MANUFACTURE OF ALPHA+BETA (ALPHA+BETA)-TYPE TITANIUM ALLOY

摘要

PURPOSE:To manufacture, at a low cost, an alpha+beta-type Ti alloy material having strength and ductility equal to those of parts to which sufficient alpha+beta working is applied, by subjecting an alpha+beta=type Ti alloy to a combination of beta-working and heat treatment under specific conditions. CONSTITUTION:The alpha+beta-type Ti alloy such as the one of Ti-6Al-4V, etc., is worked at =80% reduction in area in a beta-single phase range in the range of temp. at and above beta-transus. Then the alloy is held at a temp. lower than the beta-transus by 20-90 deg.C for =4hr and cooled slowly down to 550 deg.C or below at =0.5-10 deg.C/sec cooling rate. Successively, the alloy is reheated to a temp. of 20-90 deg.C below the beta-transus, held at the temp. for less than 4hr, and cooled down to =550 deg.C at 0.5-10 deg.C/sec cooling rate. The alloy is further aged at 540-650 deg.C for 4-10hr and cooled to room temp. In this way, alpha+beta-type Ti alloy parts excellent in toughness as well as in strength can be obtained.