Study of Microstructure, Hardness and Wear Behavior of Ti-6Al-4V under Various Heat Treatment Conditions

In this study, the effect of various heat treatment conditions on the microstructure, hardness and wear resistance of the Ti-6Al-4V alloy was investigated. For this purpose, solution anneal was done in temperature range of 800C to 1050C for 1 hour and then specimens were quenched in the air and the water. One of the specimens was aged in 550C for 4 hours. Microstructural investigations by optical microscope (OM) and scanning electron microscope (SEM) showed that the solution annealing treatment at 800C leads to limited growth of precipitates without changing the microstructure and increase of hardness compared to the control sample. Also, increasing the solution annealing temperature and quenching in water causes increase of hardness and creation of and acicular martensite dual microstructure; Solution annealing in 1050C leads to formation of martensite phase that changes to irregular phase by performing aging treatment and due to this phase transformation hardness increased by 47% compared to control sample. Wear test of pin-on-disk was performed under three forces of 20N, 30N and 40N and constant speed of 0.3m/s. Wear test results and microstructural investigation of worn surfaces showed that wear mechanism was controlled by microstructure and wear resistance is not dependent on hardness; Also, the highest wear resistance is related to the sample annealed in 950C and quenched in water. Wear mechanism in all samples in most of the loads was a mixture of abrasive mechanism and oxide wear.