In the scope of refractory material processed by spark plasma sintering development for structural applications in the core of future combustion chamber, Mo-TiC alloys and Mo-TiC-Cr alloys were sintered at 1700°C with a pressure of 30 MPa. Powders of Mo, TiC and Cr were prepared by planetary ball mill in an argon atmosphere. In this dissertation, the structure, element and phase composition of alloys were investigated. The Mo-TiC alloys showed obvious intergranular brittle fracture. The fracture mode of Mo-TiC-Cr alloys, however, was changed to mixed intergranular and transgranular fracture. The obtained results demonstrated that, compared with the peaks of Mo and Mo2C from Mo-TiC, the peaks of Mo and Mo2C from Mo-TiC-Cr were deflected to the right, due to the addition of chromium forming a solid solution. The results of isothermal oxidation tests at 1200°C in air revealed that the chromium compound on the surface of the oxide layer increases and the pores decreases with the increase of oxidation time for Mo-TiC-Cr alloys. The pores of surface of the Mo-TiC alloys were less and smaller than the Mo-TiC-Cr.

Abstract. The changing law of microstructure and mechanical properties of low cost TC4 titanium alloy during deformation and annealing was investigated. The results show that the coarse cast dendritic structure of slab is broken to form rod-like or equiaxial Į+ȕ transformed microstructure by rolling deformation. After annealing, the microstructure of plate becomes uniform, moreover, the flake secondary Į separates out and the amount of primary Į phase decreases with the increase of annealing temperature and gradually tends to equiaxization. The tensile strength and ductility of plate show an increased tendency with deforming. When annealing temperature increases, the tensile strength firstly increases, and then reaches the maximum value at 820 °C, after that, it gradually decreases. The yield strength and reduction of area show decreasing trend as a whole, but the elongation has a little change. The plate has preferable matching of strength and ductile after annealing treatment at 750~820 °C for 1h in air.

The HSLA steel was studied on an MMS-200 thermal mechanical simulation in the temperature range of 800-1100 °C and a strain rate range of 0.1-1 s−1. The isothermal hot compression tests were used to investigate the flow behaviour of HSLA steel and develop a constitutive equation based on an Arrhenius equation. A modification of Zener–Hollomon parameter was considering the strain rate compensation after hot compression for improve the accuracy of the developed constitutive equation. The comparison of the results shows that the experimental flow stress data are in good agreement with the predicted flow stress data. The average absolute relative error with a correlation coefficient was found to be 6.81% and 0.96, respectively.