Effect of Y-Addition on the Mechanical Properties and Oxidation Resistance of TiAl-Mn-Mo

초록

TiAl-based alloys with the nominal chemical compositions of Ti-46.6Al-1.4Mn-2Mo-0.3C-xY (x=0.1, 0.33 and 0.6), were developed with Elemental Powder Metallurgy method. The alloys with yttrium addition had higher ultimate tensile strength, elongation and oxidation resistance than the Y-free alloy. Combined solid solution strengthening of Mn, Mo, C and Y, and the microstructural refining effect of C and Y were responsible for the increased strength at room temperature as well as at high temperature up to 800oC. Beside, Y2O3 and carbide precipitation also enhanced the strength. The room temperature ductility was improved by the microstructural refinement and by the reduction of interstitial oxygen in the a2 and g matrix. The improved ductility was evidenced by dislocations with ordinary perfect Burgers vectors in deformed g phase. The improvement of oxidation resistance by yttrium addition was attributed to the reduction of the concentration of oxygen vacancies in the TiO2 scale.