Mechanical properties of a Ti-15V-3Cr-3Sn-3Al alloy affected by the impurity hydrogen

The effect of hydrogen on the tensile properties of a beta titanium alloy (Ti-15V-3Cr-3Sn-3Al) has been studied. Cold-rolled specimens and specimens charged with hydrogen (annealed at 500 degrees C for Ih at atmospheric pressure of hydrogen gas) were solution-treated at 800 degrees C for 1 h, water-quenched and subsequently aged at 510 degrees C. Significant retardation in the age-hardening characteristics of the alloy occurred by the hydrogen charging. The effect of hydrogen charging on the ductility was not found except in the as-solution-treated condition, where slight decrease (from 65% to 60%) in the reduction in area by the charging was detected. However, when tensile tests were carried out using a unique testing machine equipped with an ultra high vacuum chamber and a quadrupole mass spectrometer, a large amount of hydrogen gas was evolved from the specimen at the moment of fracture. Furthermore, the ductility of the uncharged specimen was improved with a reduction in the hydrogen content. Thus it can be concluded that the impurity hydrogen event at the uncharged level has a strong correlation with the fracture and causes a deleterious effect on the ductility.