•AZ31B thin sheets were produced by ON-LHR technology.•The quality of ON-LHR thin sheets is superior to that of OFF-LHR.•The yield strength-grain size relationship deviates from the Hall–Petch law.•Above 563 K, qualified thin sheets without crack flaws can be produced by ON-LHR.•At 563 K, YS, UTS, FE and crack quality have a good comprehensive performance.A series of AZ31B magnesium alloy thin sheets were prepared by on-line heating rolling processing at temperatures ranging from 443 K to 623 K with intervals of 60 K to a total thickness reduction of ∼80% from initially 4 mm down to ∼0.8 mm in 7 passes. The experimental results suggest that the fracture elongation value increases rapidly at temperatures below 563 K, and then tends to be stable (563 K-623 K). Whereas the tendency of strength, including yield strength (YS) and ultimate tensile strength, is just an opposite one. Serrated edge in sheets manufactured with low temperatures of 443 K and 503 K. As temperature increases above 563 K, no obvious edge crack can be observed. In addition, YS is sensitive to the grain size at low temperatures while insensitive at higher temperatures, resulting in a significant deviation of the YS from the Hall-Petch (H-P) law. In order to elucidate this deviation, a model of framework is proposed which suggests that the strengthening effects of deformed grains and subgrains are weakened with the increase of the fraction of DRX grains till to losing efficacy when the latter surpasses a certain value, herein about 70%.

Mg-Al-Sn magnesium alloys have bright future in application because of good properties without rare earth elements. To study the effects of rotation rate on microstructures and mechanical properties of Mg-5Al-1Sn alloy after friction stir welding (FSW), extruded plates were butt welded by FSW with various rotation rates at constant other parameters. The results showed that after FSW, Mg17Al12 phase with poor thermal stability was dissolved, while Mg2Sn phase remained due to high dissolution point and good thermal stability. The hole-type defects were observed at 600 rpm, and the weld joint was with no defects at 800~1100 rpm. The weld joint at 800 rpm gave a maximum ultimate tensile strength (UTS), which was 91% of the base material (BM). After FSW, both UTS and elongation of weld joints decreased compared with the BM, caused by the soften region between nugget zone (NZ) and thermo-mechanically affected zone (TMAZ), the dissolution of Mg17Al12 phases, the residual stress and dislocation content in the TMAZ, and the textural variation. With increasing rotation rate from 600 to 1100 rpm, the UTS of weld joints first increased and then decreased, while the elongation kept mostly unchangeable due to the common action of multifactors.

Coating of graphene and graphene/polymer composites on metals improves the corrosion resistance of metal substrates. On other hand, graphene embedded inside metal (especially Mg) matrices increases or decreases corrosion, is a crucial factor and must be explored. In present study, electrochemical behaviors of magnesium alloys (AZ31 and AZ61) and their composites reinforced with graphene nanoplatelets (GNPs) were carried out in 3.5% NaCl solution by polarization method. The surface morphology of composites before and after corrosion tests were analyzed using scanning electron microscopy. Experimental results revealed that presence of graphene nanoplatelets in different matrices decrease corrosion resistance of composites. This may be attributed to presence of graphene nanoplatelets which activates the corrosion of magnesium/alloys due to the occurrence of galvanic corrosion and this effect increases with increasing graphene nanoplatelets content. Further, an appropriate model describing the corrosion mechanism was proposed.

•Biodegradable as-extruded Mg-Sr alloys were fabricated.•Microstructure of alloys changed with increasing Sr content.•Mechanical properties of alloys could be controlled by adjusting the Sr content.•Corrosion properties of alloys decreased with increasing Sr content.•As-extruded Mg-0.5Sr alloy was potential for orthopedic application.In this study, as-extruded Mg-Sr alloys were studied for orthopedic application, and the microstructure, mechanical properties, bio-corrosion properties and cytotoxicity of as-extruded Mg-Sr alloys were investigated by optical microscopy, scanning electron microscopy with an energy dispersive X-ray spectroscopy, X-ray diffraction, tensile and compressive tests, immersion test, electrochemical test and cytotoxicity test. The results showed that as-extruded Mg-Sr alloys were composed of α-Mg and Mg17Sr2 phases, and the content of Mg17Sr2 phases increased with increasing Sr content. As-extruded Mg-Sr alloy with 0.5 wt.% Sr was equiaxed grains, while the one with a higher Sr content was long elongated grains and the grain size of the long elongated grains decreased with increasing Sr content. Tensile and compressive tests showed an increase of both tensile and compressive strength and a decrease of elongation with increasing Sr content. Immersion and electrochemical tests showed that as-extruded Mg-0.5Sr alloy exhibited the best anti-corrosion property, and the anti-corrosion property of as-extruded Mg-Sr alloys deteriorated with increasing Sr content, which was greatly associated with galvanic couple effect. The cytotoxicity test revealed that as-extruded Mg-0.5Sr alloy did not induce toxicity to cells. These results indicated that as-extruded Mg-0.5Sr alloy with suitable mechanical properties, corrosion resistance and good cytocompatibility was potential as a biodegradable implant for orthopedic application.

•A high-strength Mg-5Zn-1Ce-0.5Y-0.6Zr alloy with low RE content was developed.•A high yield strength (407 MPa) and moderate elongation (7.1%) are achieved.•The yield strength is much higher than those of several Mg-Gd-Y series alloys.•The high strength is related to fine grains, precipitates and texture.A new high-strength Mg-5Zn-1Ce-0.5Y-0.6Zr (wt%) magnesium alloy with low rare-earth content was developed by extrusion and direct aging. The peak-aged sample exhibited a yield strength of 407 MPa and an ultimate tensile strength of 421 MPa. The yield strength of this alloy was much higher than those of several Mg-Gd-Y alloys to which large amounts of rare-earth metals were added. The high strength of the alloy was closely related to the combined contributions of ultra-fine dynamically recrystallized grains (about 1 μm diameter), numerous nanoscale precipitates, and a strong basal texture.

The as-extruded Mg–Sn–Ca alloys were prepared and investigated for orthopedic applications via using optical microscopy, scanning electron microscopy, X-ray diffraction, as well as tensile, immersion and electrochemical tests. The results showed that, with the addition of 1% Sn and the Ca content of 0.2%–0.5%, the microstructure of the as-extruded Mg–Sn–Ca alloys became homogenous, which led to increased mechanical properties and improved corrosion resistance. Further increase of Ca content up to 1.5% improved the strength, but deteriorated the ductility and corrosion resistance. For the alloy containing 0.5% Ca, when the Sn content increased from 1% to 3%, the ultimate tensile strength increased with a decreased corrosion resistance, and the lowest yield strength and ductility appeared with the Sn content of 2%. These behaviors were determined by Sn/Ca mass ratio. The analyses showed that as-extruded Mg–1Sn–0.5Ca alloy was promising as a biodegradable orthopedic implant.

Graphene and its derivatives have been extensively used as reinforcing agents owing to their high mechanical properties. In the present work, an attempt is made to synthesize graphene nanoplatelets (GNPs) reinforced Mg–6Zn alloy using a disintegrated melt deposition method. The effects of GNPs on microstructural and mechanical properties of alloy were investigated. The microstructural analysis revealed uniform dispersion of GNPs throughout composite matrix along with refined grain size. The results of strength measurements indicated that addition of GNPs lead to increase in microhardness, tensile and compression strengths. The increased strength of synthesized composites may be attributed to grain refinement, uniform dispersion of GNPs, changes in basal textures and basic strengthening mechanisms. Moreover, comparison of synthesized composites with Mg–6Zn–CNTs composites revealed that GNPs have high potential to replace CNTs because GNPs are 4–6 times cheaper than CNTs.

The effects of V-bending process, continuous bending process and combination process on the microstructure and mechanical properties and formability of an AZ31 magnesium alloy sheet were investigated. The experimental results showed that no twins were found in the microstructure of all samples after processes due to the fine grain. The V-bending and continuous bending processes were proved to be an effective approach to modify the mechanical properties and formability. While the samples after the combination process exhibited better mechanical properties and formability than the single processed sample. The yield strength significantly decreased with the value of 100 MPa and the fracture elongation enhanced to 18.3% at room temperature. The Erichsen value was 5.0 mm which was significantly increased by 117% compared with as-received sample. The superior formability of combination processed samples was mainly attributed to the smaller r-value and n-value.

A novel low-cost method for melt purification of magnesium alloys, the melt self-purifying technology (MSPT), has been developed successfully based on a low temperature melt treatment (LTMT) without adding any fluxes. The iron solubility in the molten liquid of magnesium and its alloys, and the settlement velocity of iron particles were calculated. It is shown that the low temperature melt treatment is an effective method to decrease the impurity Fe content in magnesium and its alloys. Without any additions, the Fe content in the AZ31 alloy was reduced to 15 ppm from the initial 65 ppm, and the Fe content in the AZ61 melt was decreased to 20 ppm from the initial 150 ppm after the low temperature melt treatment. The results also showed that the Fe content in AM60 and AM50 dropped to 15 and 18 ppm, respectively, from the initial 150 ppm after the low temperature melt treatment. For ZK 60, the Fe content in the melt down to less than 5 ppm was achieved. After the low temperature melt treatment, the Si content in the above alloys was also decreased obviously.

Hot tearing is often a major casting defect in magnesium alloys and has a significant impact on the quality of their casting products. Hot tearing of magnesium alloys is a complex solidification phenomenon which is still not fully understood, it is of great importance to investigate the hot tearing behaviour of magnesium alloys. This review attempts to summarize the investigations on hot tearing of magnesium alloys over the past decades. The hot tearing criteria including recently developed Kou's criterion are summarized and compared. The numeric simulation and assessing methods of hot tearing, factors influencing hot tearing, and hot tearing susceptibility (HTS) of magnesium alloys are discussed.

The microstructure and mechanical properties of as-extruded and as-aged Mg–4Zn–1.5Al (in wt%) alloy rods were investigated systematically. The results indicate that the addition of Sn to as-extruded Mg–4Zn–1.5Al alloys can lead to the formation of Mg2Sn and refine the grain size as the Sn content is less than 2%. However, higher Sn results in the coarsening of grain and secondary precipitates. Among the as-extruded alloys, Mg–4Zn–1.5Al–2Sn alloy exhibits optimal combination of strength and ductility, the ultimate tensile strength (UTS), yield strength (YS) and elongation (εf) are 305 MPa, 195 MPa and 15%, respectively. A subsequent T5 heat treatment was carried out on as-extruded Mg–4Zn–1.5Al–2Sn. After aging at 150 °C for 5–50 h, there are much more secondary precipitates, which results in improved strength and ductility. The best combination of strength and ductility is as-extruded ZAT422 alloy aging at 150 °C for 40 h, the UTS, YS and ɛf are 314 MPa, 236 MPa and 18%, respectively.

•Biodegradable Mg–Sn implant alloys were prepared by sub-rapid solidification.•Secondary dendrite arm spacing of alloys decreased with increasing Sn content.•Corrosion rates of alloys increased significantly with increasing Sn content.•Mg–1Sn and Mg–3Sn alloys were harmless to MG63 cells.In this study, biodegradable Mg–Sn alloys were fabricated by sub-rapid solidification, and their microstructure, corrosion behavior and cytotoxicity were investigated by using optical microscopy, scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, X-ray diffraction, immersion test, potentiodynamic polarization test and cytotoxicity test. The results showed that the microstructure of Mg–1Sn alloy was almost equiaxed grain, while the Mg–Sn alloys with higher Sn content (Sn ≥ 3 wt.%) displayed α-Mg dendrites, and the secondary dendrite arm spacing of the primary α-Mg decreased significantly with increasing Sn content. The Mg–Sn alloys consisted of primary α-Mg matrix, Sn-rich segregation and Mg2Sn phase, and the amount of Mg2Sn phases increased with increasing Sn content. Potentiodynamic polarization and immersion tests revealed that the corrosion rates of Mg–Sn alloys increased with increasing Sn content. Cytotoxicity test showed that Mg–1Sn and Mg–3Sn alloys were harmless to MG63 cells. These results of the present study indicated that Mg–1Sn and Mg–3Sn alloys were promising to be used as biodegradable implants.

•Linear sections exist in compression strain–stress curves of hexagonal Mg–Li alloys.•Compression twins after tension ones cause the gradient decrease of linear section.•Zn affects the solidification style and the texture of hexagonal Mg–Li alloy.Mg–3Li and Mg–3Li–2Zn alloys were prepared by metal model casting method and extruded at 573 K with the extrusion ratio of 79, and samples of both cast alloys were also conducted to compression with ratios of 5% and 10%. Microstructures and mechanical properties were evaluated. The results showed that both the Zn element and the extruding were beneficial to microstructures and mechanical properties of Mg–3Li alloy. Zn addition has also affected the solidification style of the as-cast hexagonal Mg–Li alloy and resulted in the alteration of the texture. There was a descent of the gradient of the linear sections in each compressive strain–stress curve of the as-cast alloys at the strain of about 10%. This was attributed to the presentation of {10–11} compression twins, which presented after {10–12} tension twins.

•As-extruded Mg–Sn alloys with various Sn content were fabricated.•Microstructure of alloys varied with increasing Sn content.•Mechanical properties of alloys could be adjusted by controlling the Sn content.•Corrosion properties of alloys could be adjusted by controlling the Sn content.•As-extruded Mg–1Sn and Mg–3Sn alloys did not induce toxicity to cells.In this study, as-extruded Mg–Sn alloys with various Sn content were prepared and characterized for orthopedic applications. The results of microstructure observations and X-ray diffraction analysis showed that as-extruded Mg–Sn alloys were composed of α-Mg and Mg2Sn phases, and the content of Mg2Sn phase increased with increasing Sn content. The microstructure of as-extruded Mg–Sn alloy with 1 wt.% Sn was equiaxed grain, while the one with a higher Sn content was inhomogeneous microstructure and the grain size of the long elongated grains decreased with increasing Sn content. Tensile test revealed that the yield strength and ultimate tensile strength of as-extruded Mg–Sn alloys increased while the elongation decreased with increasing Sn content. Immersion and electrochemical tests indicated that the microstructure of as-extruded Mg–Sn alloys affected their corrosion properties, and the increase of Mg2Sn phase resulted from the increase of the Sn content led to a higher corrosion rate. The cytotoxicity test showed that as-extruded Mg–1Sn and Mg–3Sn alloys met the requirement of cell toxicity for orthopedic applications. Our analyses showed that as-extruded Mg–1Sn and Mg–3Sn alloys were promising to be used as biodegradable orthopedic implants.

In the present work, in order to investigate the grain refinement mechanism of AM containing Sn alloys, the as-cast AM60, AM90 alloys, and the alloys with addition of 1 wt.% Sn were fabricated by traditional casting, respectively. During the solidification of AM + Sn alloys, the morphology of divorced eutectic Mg17Al12 was refined by Mg2Sn intermetallic that served as the heterogeneous nucleation cores. The modified Mg17Al12 effectively restricted the grain growth and resulted in a grain refinement. As a result, the yield strength of as-cast AM alloys was significantly enhanced by addition of Sn, while the ductility also improved. Moreover, the edge-to-edge model was employed to predict the orientation relationship between Mg17Al12 and Mg2Sn.

Conventional powder metallurgy method was used to fabricate Mg–1Cu–xAl (x=1 wt%, 3 wt%, 6 wt%, 9 wt%) alloys to study the influence of copper and aluminum on mechanical behavior of pure magnesium. Microstructural evaluation revealed the presence of Mg17Al12 and Mg2Cu intermetallic phases in synthesized alloys. Experimental results exhibited that the increase in aluminum content lead to increase in Vickers hardness, 0.2% yield strength and ultimate strength (both in tension and compression). The tensile failure strain of alloys increases till the threshold of 3 wt% Al is reached. The decline in failure strain for the alloys containing higher wt% Al contents (i.e., 6 and 9 wt% Al), might be attributed to the formation of brittle intermetallic phase Mg17Al12.

Mg–3Al–1Zn–CNTs composites, with different weight fractions (0.25–1.0 wt%) of carbon nanotubes (CNTs) were successfully fabricated via a powder metallurgy method. The processing parameters were adopted in such a way to have uniform dispersion of short length CNTs without any damage, as well as refined and dissolved β phases structures throughout the composite matrix. The composite exhibited impressive increase in microhardness (about +23%) and tensile failure strain value (about +98%) without significant compromise in tensile strength, compared to the un-reinforced Mg–3Al–1Zn alloy. The synthesized composites can be used in automotive and aerospace industries due to their low density and high specific strength.

As-extruded Mg–5Sn–1Zn–xAl alloys (x=1, 3, and 5) were fabricated by hot extrusion. The experimental results revealed that the yield strength of alloys initially decreased and then increased with the increase of Al content. These changes were mainly attributed to the difference in crystallographic texture and volume fractions of second phases. The ultimate tensile strength, yield strength, and elongation of the alloys were greater than 310 MPa, 227 MPa, and 11%, respectively. The strain hardening ability of the alloys was also discussed.

In present study, the microstructure, mechanical and electrochemical properties of aluminum–graphene nanoplatelets (GNPs) composites were investigated before and after extrusion. The contents of graphene nanoplatelets (GNPs) were varied from 0.25 to 1.0 wt.% in aluminum matrix. The composites were fabricated thorough powder metallurgy method, and the experimental results revealed that Al-0.25%GNPs composite showed better mechanical properties compared with pure Al, Al-0.50%GNPs and Al-0.1.0%GNPs composites. Before extrusion, the Al-0.25%GNPs composite showed ~13.5% improvement in ultimate tensile strength (UTS) and ~50% enhancement in failure strain over monolithic matrix. On the other hand, Al-0.50%GNPs and Al-0.1.0%GNPs composites showed the tensile strength lower than monolithic matrix. No significant change was observed in 0.2% yield strength (YS) of the composites. However, the extruded materials showed different trends. The 0.2%YS of composites increased with increase in GNPs filler weight fractions. Surprisingly, UTS of composites with 0.25 and 0.50% GNPs was lower than monolithic matrix. The failure strain of the baseline matrix was enhanced by ~46% with 0.25% graphene nanoplatelets. The superior mechanical properties (in terms of failure strain) of the Al-0.25%GNPs composite maybe attributed to 2-D structure, high surface area and curled nature of graphene. In addition, the corrosion resistance of pure Al and its composites reinforced with 0.5 and 1.0 wt% GNPs was also investigated. It was found that the corrosion rate increased considerably by the presence of GNPs.

•The Mg-graphene/CNTs composites are fabricated in present work.•Synergetic effect of MW–CNTs and GNPs in magnesium matrix is investigated.•MW–CNTs intercalates between Graphene sheets to form 3D hybrid structures.Graphene nanoplatelets (GNPs) are novel reinforcing fillers due to their fascinating mechanical properties. However, their unique mechanical properties rapidly devolve as the sheets aggregate due to strong van der Waals forces and π–π attractions, therefore limiting their applications in metal matrix composites. In present work, the rapid aggregation of two-dimensional GNPs is inhibited by intercalating one-dimensional multi-walled carbon nanotubes (MW-CNTs). The long and flexible MW-CNTs bridge adjacent GNPs to form three dimensional hybrid structures which prevent their aggregation, thus resulting in a high contact area between CNTs + GNPs hybrid structure and the matrix. The composite reinforced with hybrid (GNPs and CNTs) reinforcement exhibited higher failure strain than those reinforced with individual GNPs and MW-CNTs. Compared to pure Mg, the Mg–1Al–0.6 wt.%(CNTs + GNPs) composite exhibited improvement in elastic modulus, 0.2% yield strength, ultimate tensile strength and failure strain (+17%; +19%; +15% and +137%, respectively). The impressive increase in tensile failure strain (%) confirmed significant synergetic effect between GNPs and MW-CNTs.

Thermal conductivity is a key parameter for thermal design and management of the electronic components in their passive cooling processes. In this work, thermal and electrical conductivities of six groups of binary Mg alloys (Mg–Al, Mg–Zn, Mg–Sn, Mg–Zr, Mg–Mn, and Mg–Ca) in as-cast, as-solution, and annealed states were measured and the corresponding microstructures were observed. In both as-cast and as-solution states, thermal/electrical conductivities of the six groups of Mg alloys decreased with composition. Effects of solution treatment and annealing on thermal/electrical conductivities of the as-cast samples were also investigated and discussed. Moreover, the specific thermal/electrical resistivity (thermal/electrical resistivity increment of the alloy derived from one atom addition) of the solute elements for Mg alloys was drawn as follows, Zn < Al < Ca < Sn < Mn < Zr. Atomic volume difference of the solute elements with Mg atom (ΔV/VMg), valency, and configuration of extra-nuclear electron of the solute were believed as the main reasons for the differences.

In recent years, graphene has attracted considerable research interest in all fields of science due to its unique properties. Its excellent mechanical properties lead it to be used in nano-composites for strength enhancement. This paper reports an Aluminum–Graphene Nanoplatelets (Al/GNPs) composite using a semi-powder method followed by hot extrusion. The effect of GNP nano-particle integration on tensile, compressive and hardness response of Al is investigated in this paper. It is demonstrated that 0.3 wt% Graphene Nanoplatelets distributed homogeneously in the matrix aluminum act as an effective reinforcing filler to prevent deformation. Compared to monolithic aluminum (in tension), Al–0.3 wt% GNPs composite exhibited higher 0.2% yield strength (+14.7%), ultimate tensile strength (+11.1%) and lower failure strain (−40.6%). Surprisingly, compared to monolithic Al (in compression), Al–0.3 wt% GNPs composite exhibited same 0.2% compressive yield strength and lower ultimate compression strength (−7.8%), and lower failure strain (−20.2%). The Al–0.3 wt% GNPs composite exhibited higher Vickers hardness compared to monolithic aluminum (+11.8%). Scanning electron microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate the surface morphology, elemental percentage composition, and phase analysis, respectively.

Deposition property and microstructure evolution of nano-scaled ZrNbAlNx multilayer films, which present a periodic modulation structure of ZrNx/AlNx/ZrNx/NbNx with different N atomic concentration, deposited using a reactive unbalanced magnetron sputtering system was investigated by varying N2 flow rate. Multilayer films were characterized using X-ray diffraction, Scanning electron microscope, Transmission electron microscope, Laser Raman spectrometer and nano-indentation tester. The experimental results show that the nano-scaled multilayer film displays a columnar growth at N2 flow rate of 4 sccm and an un-columnar deposition at N2 flow rate of 33 sccm. The increase in N2 flow rate leads to increase of N atomic concentration and decrease of Zr atomic concentration. Microstructure of multilayer films indicates a variation from close-packed hexagonal structure with (1 0 1) preferred orientation to faced cubic structure with (1 1 1) preferred orientation. The Raman spectrums position presents a shift corresponding to microstructure evolution of multilayer films. Maximum micro-hardness value of multilayer film is 22 GPa at N2 flow rate of 27.5 sccm.Highlights► A novelty ZrNbAlNx multilayer film with different N2 flow rate was deposited. ► Chemical composition and property of multilayer films were affected by N2 flow rate. ► Vickers hardness value shows a typical variation with the increase in N2 flow rate.

•We develop binary Mg–Zn sheet with high conductivity.•We develop binary Mg–Zn sheet with competitive mechanical property.•Texture weakening shows positive contribution to conductivity.•Mechanism for develop high conductivity alloy is proposed.In this work, Mg–Zn sheets with high conductivity, refined grain structure and acceptable strength were successfully developed by cold rolling and the following aging treatment. Rolling process decreased the electrical conductivity of the extruded sheet, while the following aging would improve the corresponding conductivity remarkably. The obtained highest electrical conductivity of the Mg–Zn sheet was 20.01 (106 S m−1), noting electrical conductivity of the pure Mg is 22.8 (106 S m−1). Cold rolling and aging treatment induced static recrystallization and the grain size was greatly refined. The mean grain size of the 18% cold rolled alloy was reduced to about 8 μm after aging treatment, much smaller than the original grain size (about 50 μm in average). Moreover, peak micro-hardness of the rolled alloys could reach as high as 70 HV during aging. Specially, basal texture weakening happened for largely cold rolled and aged alloy, which would contribute to increase electrical conductivity of the sheet; texture weakening was thus considered as a new noble method to develop high-quality thermal transportation Mg alloys.

Lithium alloying additions are verified to be an effective way to enhance the room temperature formability of magnesium. In this work, AZ31 (Mg–3 wt% Al–1 wt% Zn) alloys with different lithium additions (0–5 wt%) were melted and extruded to 2 mm thick sheets at 380 °C. The microstructure and texture evolution were investigated by optical microscopy, X-ray diffraction (XRD) and electronic backscattered diffraction (EBSD). Tensile tests along three directions were carried out at room temperature, to access the mechanical properties and anisotropy. It was found that the mechanical anisotropy of the as-extruded AZ31 alloy was modified remarkably with lithium additions and AZ31 alloy with 5% Li content was found to have the smallest planar anisotropy and enhanced elongation. Lithium additions also increased the rotation of basal poles in the transverse direction, which was attributed to decreased c/a ratio and refined recrystallized structure. The thickness reduction and width reduction during tensile test were also measured and discussed.

Second phases in the AZ31 as-cast magnesium alloys with different Sr contents (0, 0.1, 0.5, 1.0, 2.0, and 5.0 wt%) were investigated using scanning electron microscopy, energy dispersive spectrometry, differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. The results indicated that the Mg21(Zn, Al)17 phase with small amount was formed in the AZ31 as-cast alloy without Sr addition, in addition to the Mg17Al12 phase. At the same time, the alloy with the addition of 0.1 wt% Sr mainly consisted of the α-Mg, Mg17Al12, Mg21(Zn, Al)17, and Al4Sr phases. In addition, the α-Mg, Mg21(Zn, Al)17 and Al4Sr phases were found to be the main second phases for the alloy with the addition of 0.5 wt% Sr. However, only the α-Mg, Al4Sr and (Mg, Al)17Sr2 phases were mainly formed in the AZ31 alloy with the addition of 1.0 wt% Sr. As for the alloys with the additions of 2 and 5 wt% Sr, their as-cast microstructures were mainly composed of the α-Mg and (Mg, Al)17Sr2 phases.

The as-cast and as-extruded Mg–9Li–1Al–xCa alloys (x = 0, 0.2; wt%) were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2. The microstructures of the as-cast and as-extruded Mg–9Li–1Al–xCa alloys were observed to investigate the effect of calcium (Ca) element on the Mg–9Li–1Al (LA91) alloy, and the crystallographic calculations between Al2Ca and the matrix (α-Mg and β-Li phases) were examined on the basis of the edge-to-edge matching model. The experimental results indicate that the addition of 0.2 wt% Ca into LA91 alloy reduce the size of the α-Mg phases in the as-cast alloy and that of β-Li phases in the as-extruded alloy due to the Al2Ca particles distributed inside the matrix. Crystallographic calculation results suggested that there is a good crystallographic matching between the matrix and Al2Ca, which confirmed that Al2Ca particles can act as a heterogeneous nucleation site for both α-Mg and β-Li phases and were effective grain refiners for LA91 alloy.

A series of Zr56Co44−xAlx (x = 12, 14, 16 and 18, respectively) bulk metallic glasses (BMGs) are obtained using water-cooled copper mold casting technique. With increasing Al/Co ratio, the BMGs exhibit a better thermal stability of the supercooled liquid, higher strength and larger plasticity. The origin of the high specific fracture strength lies in the increased strength and reduced mass density (more Al). Among them, Zr56Co26Al18 BMG has a high fracture strength (∼2477 MPa), small density (∼6.31 g/cm3) and very high specific fracture strength (∼3.92 × 105 Nm kg−1) exceeding the values of commercial stainless steel, light alloys as well as some popular BMGs. It seems to be a promising structural material owning to its excellent GFA, large plasticity and high specific strength.Graphical abstractHighlights► A series of Zr–Co–Al bulk metallic glasses with high strength and large plasticity. ► The higher Poisson's ratio favors larger plasticity and vice versa. ► Zr56Co26Al18 BMG: a promising structural material. ► High specific fracture strength origins from increased strength and reduced density.

A density functional theory study was performed on fullerene derivatives C60X18 and C70X10 (X = H, F, Cl, and Br). The calculated results show that the lowest energy isomers are IPR-satisfying for C60X18 (X = H, F, Cl, and Br). It is found that the addition patterns of X (X = Cl and Br) are different from those of X (X = H and F) for C60, demonstrating that the stability of fullerene derivatives is partly attributed to the steric repulsion and electronegativity of added atoms. However, the lowest energy isomers are IPR-violating for C70X10 (X = H, F, and Cl), suggesting that many more fullerene derivatives may violate the isolated pentagon rule.

The mechanical property of Zr56Co28Al16 bulk metallic glasses (BMGs) under compression test at room temperature was investigated. The alloy exhibited high fracture strength of approximately 2136 MPa and a pronounced plastic strain of 10.2%. No strain-hardening behavior was observed. The evolution of the morphology of the shear bands on the lateral surface of the as-cast samples was studied using scanning electron microscopy (SEM). The plasticity can be attributed to the formation and interaction of multiple shear bands during deformation. The crystallization behavior was studied by differential scanning calorimetry (DSC) at different heating rates. The activation energies of the glass transition (Eg), the onset of the crystallization (Ex) and the two stages of the crystallization (Ep1 and Ep2) were calculated to be Eg = 303.2 ± 13.5, Ex = 316.4 ± 37.9, Ep1 = 336.2 ± 36.2 and Ep2 = 362.0 ± 29.5 kJ/mol, respectively. The crystallization behavior research of this alloy indicates that the precipitation of the B2-ZrCo phase may be further utilized to promote the ductility of the ZrCoAl BMG composites.Research highlights► A study of the mechanical properties and crystallization of a ZrCoAl BMG. ► high fracture strength and high plastic strain. ► B2 phases may promote ductility of the BMG composites

The influence of alloying elements on the stacking fault energy (SFE) of Mg–Y–Zn–Zr alloys was calculated by using first-principles, and the microstructure of as-cast Mg-1.05Y-0.79Zn-0.07Zr (mole fraction, %) alloy prepared by conventional casting was investigated by SEM, TEM and HRTEM. The block-like long period stacking ordered (LPSO) phase, the lamellar LPSO phase and stacking faults were observed simultaneously and the lamellar LPSO structure and stacking faults were both formed on (0001)α-Mg habit plane and grown or extended along [01i0]α-Mg direction. The calculation results by the first-principles showed that the addition of Y can sharply decrease the stacking fault energy of the Mg–Zn–Y–Zr alloy, while Zn slightly increases the stacking fault energy of the alloy. The influence of stacking fault energy on the formation of LPSO was discussed. It shows that LPSO may nucleate directly through stacking faults and the lower stacking fault energy was in favor of formation of LPSO.

The decomposition of the coarse primary M2C carbide in M2 high speed steel was investigated by using optical microscope, scanning electron microscope, energy dispersive spectrometer and X-ray diffraction analysis. It is indicated that the SEM observation using deeply etched samples can clearly reveal the details of the decomposition products of primary M2C eutectic carbides. The MC is granular and M6C is peanut-shaped in the decomposition products, and the decomposition products are found to be very small in the size. With the increase of annealing temperature and duration, part of the peanut-shaped M6C carbides change to simple skeleton-shaped ones. The phase transformation refinement of primary M2C carbides in M2 steel by the decomposition of metastable M2C carbides at high temperature can be obtained if suitable annealing parameters are applied. The complete decomposition of M2C to M6C and MC will occur when (1 100 °C, 4 h) or (1 150 °C, 2 h) annealing treatment is employed in M2 high speed steel.

AbstractThe effects of Sc addition on the microstructure and mechanical properties of the ZK60 wrought magnesium alloy were investigated by using optical microscope, scanning electron microscopy, X-ray diffraction and tensile testing. The experimental results show that a minor Sc addition to ZK60 alloy has an obvious effect on the refinement of the microstructure of the ZK60 alloy. During hot extrusion, incomplete dynamic recrystallization occurs in all the alloys, and the recrystallized grains become much finer with increasing Sc addition. The tensile strengths of ZK60 evidently increase with the addition of Sc, but the elongations decrease. The ZK60 alloy with 0.6% (mass fraction) Sc addition is found to have the tensile strength of about 350 MPa and the yield strength of about 280 MPa. After T6 heat treatment, the tensile strength of the alloy containing 0.6% Sc remains almost unchanged. However, the yield strength of the alloy increases up to 352 MPa, and the ratio of the tensile strength to the yield strength is close to 1.

MoSx-CrTiAlN film was deposited on Mg alloy substrates using unbalanced magnetron sputtering. First of all, the CrTiAlN layer was synthesized in a gas mixture of Ar + N2, and then the MoSx layer on CrTiAlN were deposited by a single MoSx target. The composition, structure and tribological property of MoSx-CrTiAlN film were characterized by X-ray photoelectron spectrometry, X-ray diffraction, transmission electron microscopy and ball-on-disc tester. The experimental results show that crystallography structure of CrTiAlN layer is FCC whilst the MoSx layer has a mixed microstructure with hexagonal and amorphous state. The coefficient of friction of MoSx-CrTiAlN film is a function of load and shows a steady decreasing with the increasing in applied load.Highlights► We have successfully prepared MoSx-CrTiAlN film on Mg alloy by unbalance magnetron sputtering. ► We check structure and tribological of MoSx-CrTiAlN multi-layer film by XRD, XPS, TEM and ball-on-disc tester. ► The coefficient of friction of MoSx-CrTiAlN multi-layer film is a function of applied load. ► Antifriction property of MoSx-CrTiAlN film significantly outperforms that of CrTiAlN film.

The research and development status of casting magnesium alloys including the commercial casting alloys and the new types casting alloys are reviewed, with more attention to microstructure and mechanical properties of modified-AZ91, AM60 and WE43 alloys with various additions, and new types of low cost casting alloys and high strength casting alloys. The modification and/or refinement of Mg2Si phase in Mg–Al–Si based casting alloys by various additions are discussed and new purifying technologies for casting magnesium alloys are introduced to improve the performance. The modified AZ81 alloy with reduced impurities is found to have the tensile strength of 280 ± 6 MPa and elongation of 16% ± 0.7%. The fatigue strength of AZ91D alloy could be obviously improved by addition of Ce and Nd. The Mg–16Gd–2Ag–0.3Zr alloy exhibits very high tensile and yield strengths (UTS: 423 MPa and YS: 328 MPa); however, its elongation still needs to be improved.