Microstructural evolution and FCC twinning behavior during hot deformation of high temperature titanium alloy Ti65

Although the development of titanium alloys with working temperatures above 600 degrees C faces enormous difficulties and challenges, the related research has not stopped. In the present work, detailed analyses on microstructure evolution and hot deformation behavior of a new temperature resistant 650 degrees C titanium alloy Ti65 were investigated from micrometer scale to nanometer scale. The results revealed that lamellar alpha grains gradually fragmentized and spheroidized during the alpha + beta phase region compression and the orientation of the c-axis of alpha grains gradually aligned to radial directions, forming two high Schmid factors (SFs) value texture eventually with the increase of strain to 0.7. Moreover, there were some strengthening characters in the alpha + beta phase region such as lenticular alpha(s) and nano silicide (TiZr)(6)Si-3. In the beta phase region, fine equiaxed dynamic recrystallized (DRX) beta grains were formed. Besides, the variant selection of alpha martensite followed Burgers orientation relationship during the compression process. The main deformation mechanisms of the alpha + beta phase region were dislocation slip and orientation dependent spheroidization. Whereas, the deformation process in the beta phase region was controlled by beta grain DRX. Interestingly, many nano scale FCC twins were generated at the interface of alpha lath during deforming in the beta phase region, which was firstly observed in Ti65 alloy. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.