Effect of Microstructure on Stress Rupture Properties of Electron Beam Welds of Ti-24Al-15Nb-1.5Mo/TC11 Dual-alloy

Abstract:

The effect of microstructures obtained by different heat treatments on the stress rupture properties of Ti-24Al-15Nb-1.5Mo/TC11 dual-alloy with electron beam welds has been evaluated. The results indicate that after double heat treatment, the microstructures of the weld and the heat affected zone of Ti-24Al-15Nb-1.5Mo alloy consist of large quantities of strip α and α2 phases which are parallel arranged and vertical to the direction of stress, and there are also intermittent grain boundaries α and α2 phases. All these make microcracks connect and extend fast, reducing the rupture life of specimens. However, under the same deformation condition, the welding seam after gradient heat treatment consist of plenty of fine strip and equiaxed α, α2 phases and a few large size α, α2 phases. Under the long time load, mcirocracks consume more energy or spend more time in order to go round or go through the large size grains. The long time load at high temperature has little impact on the microhardness.

Key words:dual alloy welding seam; stress rupture property; microhardness