•A three-zone model was proposed for simulating sample homogeneity.•Stress has higher impact on sample homogeneity than temperature.•Electro-thermal effects cannot reduce but may increase the sintering heterogeneity raised by uneven stress distribution.In this paper, we studied the microstructure and mechanical properties of carbonyl iron powder materials fabricated by electric current activated sintering at temperatures of 650–800 °C under pressures of 20–50 MPa. All sintered samples consist of fine ferrite and spheroidized particles. The average density, average hardness and bending strength increase with an increase in either temperature or pressure. In particular, non-uniform distributions of density and hardness within the sintered samples were discussed, and a three-zone model was also proposed for simulation. Experimental and simulation results reveal that (1) the temperature distribution is homogeneous during sintering. (2) the inhomogeneous axial stress distribution, which is caused by a unidirectional load, is responsible for a poor sintering uniformity. In order to obtain homogenous sintering, more attention should be paid to axial stress distribution rather than to temperature distribution in electric current activated sintering of high thermal conductivity conductive powders like carbonyl iron powders.

•The Al2O3–ZrO2 (Y2O3) eutectic was firstly prepared by spark plasma sintering.•The specimen sintered at 1600 °C shows a typical eutectic microstructure.•The specimen sintered at 1500 °C manifests a transitional microstructure.•The specimen sintered at 1500 °C exhibits high mechanical properties.Fully densified Al2O3–ZrO2 (Y2O3) eutectic ceramics without any binders were fabricated by a novel and efficient way, namely spark plasma sintering. The morphology of the specimen sintered at 1600 °C shows a typical lamellar eutectic microstructure, while the one sintered at 1500 °C manifests a transitional microstructure between sintering and casting. The latter specimen also exhibits high mechanical properties: the Vickers hardness and fracture toughness of it are 17.5±0.3 GPa and 7.4±0.4 MPa m1/2, respectively.

•Fine-grained 93W–5.6Ni–1.4Fe heavy alloy was prepared by spark plasma sintering.•Split Hopkinson pressure bar was used to evaluate dynamic deformation behavior.•Deformation behavior and microstructure after dynamic compression was analyzed.•Effect of microstructure on deformation behavior was analyzed by adapted KHL model.In this study, split Hopkinson pressure bar was used to evaluate the dynamic deformation behavior of the 93W–5.6Ni–1.4Fe heavy alloy (93WHA) prepared by spark plasma sintering (SPS) and conventional liquid-phase sintering (CLS). The influence of the microstructural characteristics (such as W grain size, W–W contiguity and volume fraction of the matrix) on the dynamic deformation behavior was investigated. In contrast to the conventional liquid-phase sintered 93WHA, the spark plasma sintered 93WHAs exhibit high yield strength and flow stress during high strain rate compression, due to the decreased mean matrix thickness (the mean matrix thickness is related to the W grain size, W–W contiguity and volume fraction of the matrix). The decreased matrix mean thickness and increased number of grain boundaries in the spark plasma sintered 93WHAs result in an increase of aspect ratio of W grains in the core of the deformed specimen and a decreased width of shear band along the direction of maximum shear stress.

Ti–47Al–2Nb–2Cr–0.15B (at%) alloy was brazed with an amorphous Ti–25.65Zr–13.3Cu–12.35Ni–3Co–2Mo (wt%) alloy foil in vacuum furnace. The effects of brazing temperature and testing temperature on the interfacial microstructure and mechanical property of the TiAl joints were investigated in detail. Sound TiAl brazed joints are obtained at brazing temperature of 925–1050 °C for 5 min. The joint is mainly composed of two zones, and the intermetallic phases in the joint are (Ti, Zr)2, (Cu, Ni) and Ti3Al. The brazing temperature has a significant effect on the interfacial microstructure of the TiAl joint. The room temperature shear strength of the joint first increases and then decreases with the brazing temperature. The highest room temperature shear strength of the joint is 211 MPa when the TiAl alloys were brazed at 1000 °C for 5 min. The shear strength decreases with the testing temperature and maintains above 155 MPa at a temperature below 700 °C. However, solid-state diffusion and serious oxidation in the central brazed layer II lead to the sharp reduction of the joint shear strength when the testing temperature exceeds 700 °C. All the failures of the joints occur in the central brazed layer II and the (Ti, Zr)2 (Cu, Ni) intermetallic compounds occupy most of the fracture surfaces.

In this study, tungsten heavy alloy (WHA) composites were fabricated based on tungsten (W), nickel (Ni), and iron (Fe) system. WHA composites with the composition 93W–4.9Ni–2.1Fe/95W–2.8Ni–1.2Fe–1Al2O3 were prepared by liquid-phase sintering and post-heat treatment to meet the requirement for complex mechanical performance. The relationship between the microstructural characteristics (relative density, W-grain size, and W–W contiguity) and mechanical properties was investigated. Variation in the content of W and addition of Al2O3 resulted in a significant difference in the microstructure of the two parts of W–Ni–Fe heavy alloy composite. The microstructure of the alloy significantly influenced the tensile properties of the two parts of the W–Ni–Fe heavy alloy composite; however, it did not affect their compressive deformation behaviors.

The WC–Si3N4 composites toughened by in-situ elongated β-Si3N4 grains were prepared by spark plasma sintering. By exploiting the difference in kinetics between WC grain-growth and β-Si3N4 grain-growth through sintering at an elaborate temperature or two-step sintering, composites with microstructure of in-situ elongated β-Si3N4 grains were grown sufficiently in the fine-grained WC matrix without fast-grain-growth being obtained. The relation of the microstructure and mechanical properties of the composites, as well as the toughening mechanisms, are investigated. Comparing with the fracture toughness of 6.69 MPa m1/2 for the pure WC, that of the obtained WC–Si3N4 specimen reaches 10.94 MPa m1/2.