Gang Wang
材料科学技术（英）
The hot deformation behavior of a Ti-47Al-2Cr-2Nb-0.2W-0.15B (at.%) titanium aluminide alloy fabricated by pre-alloyed powder metallurgy has been investigated by using the hot compression tests in the temperature range from 950°C to 1300°C and at the strain rates between 10-3 s-1 and 10 s-1. The processing maps have been established to evaluate the optimum hot processing conditions and reveal the instability regions. It is found that the flow stress of the investigated alloy is a strong function of the temperature and the strain rate. The investigated alloy has the optimum hot-working condition at 950°C and 10-3 s-1, since the material undergoes dynamic recrystallization to produce a fine-grained microstructure. At 1250°C and 10-3 s-1, the
alloy exhibits superplastic deformation. At 1300°C and 10-1 s-1, the cyclic dynamic recrystallization with high temperature grain coarsening takes place. The material undergoes flow instabilities at lower temperatures and higher strain rates, as predicted by the instability criterion. The processing maps demonstrate that the strain significantly affected the instability regions. The manifestations of the instabilities have been observed in the form of microvoids, wedge cracks, and surface fractures.
关键词:
Titanium aluminide
R.K. Gupta Bhanu Pant Vijaya Agarwala R.C. Agarwala P.P. Sinha
材料科学技术（英）
Reaction synthesis process has been used to develop γ titanium aluminide using elemental powders. Powder mixture of Ti-48 at. pct Al was prepared in ball mill and reaction synthesis was carried out in hot press with varying temperature and pressure. Titanium aluminide synthesized under high pressure and temperature resulted in better properties with respect to densification, homogenization response, mechanical properties and oxidation resistance as compared to that synthesized under low pressure and temperature. Al rich phases were observed in as-synthesized condition in all the experiments. However, some Ti rich phases were also found in high pressure-temperature synthesized samples. Density, hardness and tensile strength have been correlated with applied pressure through empirical relations. Variation in density with pressure is found to be logarithmic whereas hardness and tensile strength variation with pressure is polynomial.
关键词:
Titanium aluminide
,
Reaction synthesis
,
Reaction synthesis, Phase transformation
