AGE-HARDENING RESPONSE OF BETA(2) TI-AL-V

The age-hardening response of a beta(2) Ti-Al-V alloy Ti-39.5at.%Al-21 .Oat.%V has been studied. Following are melting, homogenization and so lution treatment, the alloy was aged at temperatures of 973 and 873 K for times between 3 and 96 h. Aging at 873 K resulted in a gradual and a second hardness peak was observed after longer times. X-Ray and tra nsmission electron microscopy have shown that the first increase in ha rdness was due to gamma precipitation, longer-time precipitation of a, resulting in a further hardness increase. For each aging condition, t he size of former gamma plates was observed to vary over a wide range, with gamma plates being observed to grow randomly. Finally, the obser vation of a plateau and a minimum in the aging curves at 873 K and 973 K appears to be due to an increase in gamma platelet length with incr easing aging times, which results in a loss of coherency at the gamma/ beta(2), interfaces.