Variant selection, coarsening behavior of α phase and associated tensile properties in an α plus β titanium alloy

Effect of cooling rates, i.e., air cooling and furnace cooling, after solution in alpha+ beta phase-field on variant selection, coarsening behavior of alpha phase and microstructure evolution were investigated in alpha+ beta TC21 alloy. The textures of primary alpha ( alpha p ) and lamellar alpha ( alpha L ) in beta phase transformation microstructure ( beta t ) were analysed separately, and the orientation relationship among alpha p , alpha L and the parent beta phase were studied. In addition, the influence of the microstructure characteristics on the tensile properties was investigated. The results showed that all parent beta grains, despite their different orientations, produced 12 ideal alpha L variants with the same texture components and interweave to form a basketweave beta t structure under the air-cooling condition. The alpha p without Burgers orientation relationship (BOR) with beta phase exhibited obviously texture component without overlapping the alpha L texture component. The volume fraction of alpha p in the furnace-cooled sample (about 50%) was higher than that of the air-cooled sample (about 12%), while the size of it slightly increased with decreasing the cooling rate. In each beta grain, the thick alpha L in the same orientation formed an alpha colony. A typical 3 variant colonies which were related to each other were observed. Consequently, the alpha L spatial orientation distribution showed more heterogeneity. Moreover, the BOR between alpha p and beta and the same orientation of some alpha L and the surrounding alpha p grains resulting in the overlapping of alpha p texture component and alpha L texture component. At last, the relationship between microstructure and tensile properties was analysed. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

The study investigated the effect of cooling rates on variant selection, coarsening behavior of alpha phase, and microstructure evolution in alpha+ beta TC21 alloy. Different microstructure characteristics were observed under air cooling and furnace cooling conditions, leading to variations in tensile properties of the alloy.