The Influence of Microstructures on the Notched Tensile Fracture of Ti-6Al-6V-2Sn Welds at Elevated Temperatures

Notched tensile tests of Ti-6Al-6V-2Sn welds, which were subjected to distinct post-weld heat treatments (PWHTs), were carried out in air at 150, 300 and 450 degrees C. The results were compared with those of mill-annealed base metal (MB) specimens tested at same temperatures. The notched tensile strength (NTS) of the MB specimens decreased significantly with increasing temperature. Moreover, the welds with high hardness showed notch brittleness at room temperature but had a higher NTS than the MB specimen. The presence of grain boundary alpha layer promoted grain boundary shear, therefore, reduced its notch brittleness at room temperature for the weld with the PWHT at 704 degrees C (the W-704 specimen). A lack of deformation compatibility at the interfaces between the alpha and beta phases caused interfacial separations in the MB specimen as well as void formation in the W-704 specimen, leading to the low NTS of these specimens at elevated temperatures.