材料期刊网，材料期刊，材料类期刊，材料期刊投稿

Solid state phase transformation characteristics of the body centred β(Ti) into the hexagonal closed packed α(Ti) in Ti₄₅Al₈Nb-(0, 0.3, 0.5 and 0.8 at. pct) B alloys were investigated by heat treatment to clarify γ/α₂ lamellar microstructure refinement induced by B addition. Experimental results confirmed two kinds of boron-reduced grain refinement mechanisms through refining either β phase thenα phase (β-refinement) or α phase directly (α-refinement) to refine lamellar microstructure at room temperature; however, the role of α-refinement dominated the as-cast lamellar microstructure refinement over β-refinement in Ti₄₅Al₈Nb_xB alloy. It was also found that during the α-refinement the convoluted flake- and plate-like borides along β grain boundaries assisted nucleation of α phase, and the particle-like borides near β grain boundaries impeded α phase growth.

关键词: Titanium aluminides , Phase transformation , Microstructure

Effect of Pressure and Temperature on Phase Transformation and Properties of Titanium Aluminide Obtained through Reaction Synthesis

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