Microstructures and hydrogen embrittlement of Ti–49Al alloy

Microstructures and hydrogen embrittlement of Ti–49 at% Al were investigated. Results showed that there were three kinds of microstructures formed by heat treatment at 1423, 1573 and 1703 K. The specimens which were heat-treated at 1573 K, showed better elongation than the others on tensile tests at room temperature, and this kind of specimens were used to investigate the effect of hydrogen on tensile properties of this alloy. After heat-treatment in hydrogen gas at 1073 K for 3 h, the specimens were divided into three groups. In the first group, they were tensile-tested at room temperature in vacuum; in the second group, they were heat-treated at 823 K for 1.5 h in argon gas followed by tensile-testing at room temperature in vaccum; and in the third group, they were tensile-tested at 473 or 573 K in vacuum. Results showed that for the specimens precharged with hydrogen, the elongation was decreased significantly at room temperature, and that the decreased elongation was recovered by removing hydrogen at 823 K in Ar gas, although it was not recovered to that of the specimens without hydrogen. This means that hydrogen decreases the room temperature elongation of this alloy. For the precharged specimens the elongation was also decreased at 473 and 573 K in vacuum. This may indicate that hydrides in the precharged specimens affect the tensile properties in vacuum.