Solid solution strengthening mechanism of TiAl alloy

摘要

The effect of beta stabilizers, such as Fe, Cr, V, and Nb on the microstructures and phase constituents of Ti_(52)Al_(48)-xM (x=0, 1.0, 2.0, 4.0 6.0atpercent) alloys was studied. The dependence of tensile propertie and creep rupture property of TiAl alloys on the alloying elements was investigated. Fe is the strongest B2 phase stabilizer, Cr is the second one, V is an intermediate Bw phase stabilizer, while Nb is the weakest one. The composition partitioning of Fe, Cr, V, and Nb in gamma phase is affected by the formation of B2 phase. The peaks of the tensile strengths at 25 deg C, and creep rupture life of Ti_(52)Al_(48)-xM alloys generally occur at the maximum solid solution of these elements in gamma phase, which is just before the formation of B2 phase. The improvement of tensile strengths and creep resistance with the increase of Fe, Cr, V, and Nb content is chiefly attributed to the solid solution strengthening of these elements in gamma phase. The appearance of B2 phase deteriorates the creep resistances, tensile strengths and ductilities. With respect to the maximum solid solution strengthening, an empirical equation of Cr equivalent (Cr) is suggested as following: (cr)=Cr+Mn+3/5V+3/8Nb+3/2(W+Mo) +3Fe=1.5-3.0.