High-temperature mechanical performance of directed energy deposited Ti6242S alloy

Ti6242S is a near-alpha titanium alloy that is expected to be used in engineering below 500 degrees C. The high-temperature mechanical performance including the high-temperature tensile property and the high-temperature high-cycle fatigue property is well investigated by directed energy deposition using a laser beam (DED-LB) in the paper. It is confirmed that the high-temperature tensile mechanical property can highly satisfy the forging standard for heat treated DED-LB Ti6242S. And the heat-treated DED-LB Ti6242S is of reliable high-temperature high-cycle fatigue limit relying on an analysis on the coefficient of variation of the fatigue life. It is presented that the high-temperature high-cycle fatigue life of DED-LB Ti6242S alloy is highly related to the pore position and its size. Thus a new parameter is proposed to build a relationship with the high-temperature high-cycle fatigue life. Moreover, the fatigue deformation mechanism depends strongly on the alpha and alpha' colony orientations that vary frequently and intricately in accordance with the fine microstructure morphology, leading to a reduced crack expansion rate for DED-LB Ti6242S.