Effect of Solution Treatment Temperature on Trigger Stress for Stress Induced Martensitic Transformation in Ti-10V-2Fe-3Al Alloy

Abstract

Effect of solution treatment temperature on trigger stress for stress induced martensitic transformation (SIMT) in Ti-10V-2Fe-3Al alloy has been investigated. The Ti-10V-2Fe-3Al tensile specimens were solution treated at 700-900°C and quenched to room temperature in water. All specimens, except the one solution treated at 700°C, experienced the SIMT when subjected to tensile deformation. The trigger stress was observed to initially decrease with the solution temperature increasing from 720°C to 760°C. However, it increased with the temperature increasing from 760°C to 900°C. Optical microstructure shows that with increasing solution temperature from 700°C to 740°C, β grain size of Ti-1023 alloy kept invariable. However, recrystallization was observed when solution treated at 760°C. The recrystallized β grains grew larger and larger with increasing solution treatment temperature from 760°C to 900°C. In addition, the volume fraction of primary alpha phase (αp) always decreased with increasing ST temperature from 700°C to 780°C. The microstructure was composed of only β single phase when solution treated from 830°C to 900°C. Energy dispersive spectrometry (EDS) analysis indicates that the molybdenum equivalency (Moeq) of β matrix steeply decreased initially as solution temperature increased from 700 °C to 760°C. However, it almost kept invariable with solution treatment temperature increasing from 760°C to 900°C. This evolution in trigger stress was attributed to the variations of volume fraction of primary α phase, chemical composition of β phase and the β grain size with different solution treatment temperatures.