TITANIUM ALLOY EXCELLENT IN SUPERPLASTIC WORKABILITY AND ITS MANUFACTURE AS WELL AS METHOD FOR SUPERPLASTIC WORKING OF TITANIUM ALLOY

摘要

PURPOSE:To manufacture a Ti alloy having high strength and excellent in superplastic workability by heating a Ti alloy having a specified compsn. constituted of Al, V, O, Fe, Cr, Mo and Ti to a specified temp. and thereafter rolling down this alloy at a specified temp. and draft. CONSTITUTION:A Ti alloy contg., by weight 5.5 to 6.75% Al, 3.5 to 4.5% V, =0.2% O, 0.15 to 3.0% Fe, 0.15 to 3.0% Cr and 0.85 to 3.15% Mo as well as satisfying the conditions of 0.85%=Fe+Cr=3.15% and 3%=2Fe+1.8Cr+Mo=8% and the balance Ti with inevitable impurities is heated at a temp. of the beta transformation point -200 deg.C to less than the beta transformation point. Successively, this Ti alloy is rolled down at a temp. of less than the beta transformation point at =3 draft. In this way, the high strength Ti alloy having a low superplastic working temp., low deformation resistance and high superplastic elongation and excellent in superplastic workability can be obtd. This Ti alloy is preferably subjected to recrystallization heat treatment at a temp. of the beta transformation point - 200 deg.C to less than the beta transformation point to regulate the average grain size of alpha crystals of =6mum before executing super plastic working.