Effects of Heat Treatment on Microstructures and Mechanical Properties of Ti-38644 Alloy for Aerospace Fasteners

摘要

The effects of heat treatment on microstructure and mechanical properties of Ti-38644 alloy were investigated by scanning electron microscope (SEM) and transmission electron microscopy (TEM) as well as uniaxial tensile test. The results show that when the solution temperature is lower than 845°C, the microstructure of Ti-38644 alloy is equiaxed β phase with the grain size of 20μm, and the tensile strength is about 960MPa. As raising solution temperature to 860°C, the grain size of Ti-38644 alloy increases to 100μm and the tensile strength decreased to 870MPa. There are a large number of secondary a phase precipitated from the grain boundaries and within grain of p phase undergoing aging treatment. Secondary a phase coarsens with increasing the aging temperature, leading to the decrease of tensile strength. After solution treatment at 815°C for 1.5h, water quenching plus aging at 520°C for lOh, air cooling, Ti-38644 alloy shows a better mechanical property with the tensile strength 1330MPa, elongation and reduction of area 10% and 45% respectively.