Fine Analysis of Microstructure Evolution of Ti6242 Alloy

Microstructure characterization and evolution analysis of Ti6242 alloy with equiaxed microstructure were studied by optical and scanning electronic microscopes, combining with image processing software. The origin alloy was processed under different heat treatments. Four parameters, including volume fraction V-alpha, size D-alpha, distribution density rho(alpha) and degree of aggregation E-alpha, were used to accurately describe the characteristics and evolution process of the equiaxed primary alpha phase. It is found that V-alpha, D-alpha, rho(alpha) and E-alpha all decrease with the increase of the solution temperature T, and the relationships of V-alpha vs. T and rho(alpha) vs. T satisfy the linear and parabolic law, respectively. The declining rate of V-alpha increases with the T arising and decreases with time prolonging. With the V-alpha dropping, the content of element Al in beta phase increases, while the content of Sn, Zr, and Mo decreases; the difference of the content of the four alloying elements in beta and alpha phase becomes smaller. At 850 and 800 degrees C, the [Mo](eq) of beta phase is in the [Mo](eq) range of alpha+beta and metastable beta alloy type, respectively. After being quenched in water, the beta phase shows martensitic transformation at 850 degrees C while it retains metastable beta phase at 800 degrees C.