| Effects of Al contents on the microstructure and hardness of Ti-Al-4V alloys were investigated after solution anneal and aging treatment of the alloys containing 4. 5, 6, 9 and 12% Al, respectively. The titanium alloys exhibited different α+ β⇔ βtransformation temperatures, and their hardness after solution anneal was influenced by the formation and decomposition of α` transformed from β, whereas the hardness after aging treatment was affected by the decomposition of α`, agglomeration of βgrains and precipitation of α₂(Ti₃Al). It is believed that 4% V of the alloys kept fine α₂precipitates from growing and that the α₂, precipitates, in turn, retarded the agglomeration of β-grains. α₂precipitates of about 100Å were actually observed by transmission electron microscopy in Ti-9Al-4V and Ti-12Al-4V alloys after aging treatment whereas it was not possible to observe them in Ti-6Al-4V. |
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