Tensile properties of LBW welds in Ti-6Al-4V alloy at evaluated temperatures below 450 ℃

摘要

The influence of temperatures below 450 ℃ on the tensile properties of laser beam (LB) welds in dual phase Ti-6Al-4V titanium alloy was investigated. The ultimate tensile strength of the weldment is slightly superior than that of the as-received parent materials. Conversely, the yield stress of the weldment is inferior to that of the parent metal, especially in the 150-450 ℃ range. The elongation of the weldment was about 5% lower than that of the parent metal for the entire temperature range. The prominent dislocation gliding on the pyramidal planes giving (1011) < 1123> and (1122) < 1123> type slip with low critical resolved shear stress leads to both the weldment and parent metal exhibiting the lowest ductility at a temperature range from 200 to 350 ℃. The maximum hardness in the fusion zone (FZ) corresponds to the needle-like martensite a' formed after the postsolidification phase transformation. As the temperature increases, the dimple dimension becomes larger and deeper.