Age-hardening response of β2 TiAlV

The age-hardening response of a β2 TiAlV alloy Ti-39.5at.%Al-21.0at.%V has been studied. Following are melting, homogenization and solution 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 transmission electron microscopy have shown that the first increase in hardness was due to γ precipitation, longer-time precipitation of α2 resulting in a further hardness increase. For each aging condition, the size of former γ plates was observed to vary over a wide range, with γ plates being observed to grow randomly. Finally, the observation of a plateau and a minimum in the aging curves at 873 K and 973 K appears to be due to an increase in γ platelet length with increasing aging times, which results in a loss of coherency at the γβ2 interfaces.