Influences of thermal exposure time on the microstructure and properties of Cr-9Nb alloy with exposure in vacuum condition at 800 ℃ were investigated.The results show that the microstructure of the alloy is coarsened to some extent with the increase of thermal exposure.Relative density is increased slightly in the first 50 h and then tended to be stable.Change of Vickers hardness can be ignored in a whole time and fracture toughness is decreased to 6.02 MPa·m1/2 after 100 h thermal exposure.The yield strength

compressive strength and plastic strain are increased to a peak value in initial 10 h

and then declined.Besides

the plastic strain is decreased obviously from 18.3% to 10.3% after 100 h thermal exposure.In addition

alloy still keep a high yield strength of 1 536 MPa and compressive strength of 2 203 MPa.