Although the development of titanium alloys with working temperatures above 600 ℃ 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 ℃ titanium alloy Ti65 were investigated from micrometer scale to nanometer scale.The results revealed that lamellar α grains gradually fragmentized and spheroidized during the α + β phase region compression and the orientation of the c-axis of α 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 α + β phase region such as lenticular αs and nano silicide (TiZr)6Si3.In the β phase region,fine equiaxed dynamic recrystallized (DRX) β grains were formed.Besides,the variant selection of αrhartensite followed Burgers orientation relationship during the compression process.The main deformation mechanisms of the α + β phase region were dislocation slip and orientation dependent spheroidization.Whereas,the deformation process in the β phase region was controlled by β grain DRX.Interestingly,many nano scale FCC twins were generated at the interface of αíath during deforming in the β phase region,which was firstly observed in Ti65 alloy.