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The effects of 0.3%(molar fraction,the same below)yttrium addition on hot deformability of lamellar Ti-45Al-5Nb alloywere investigated by simulated isothermal forging tests.The ingots with the nominal compositions of Ti-45Al-5Nb andTi-45Al-5Nb-0.3Y were prepared by induction skull melting.Simulated isothermal forging tests were conducted on Gleeble 1500Dthermo-simulation machine using a 6 mm in diameter and 10 mm in length compressive specimen at the deformation temperatures of1 100,1 150,1 200℃and strain rates of 1.0,0.1,0.01 s-1.The results show that yttrium addition remarkably improves hotdeformability of Ti-45Al-5Nb alloy.An appropriate hot deformation processing parameter of Ti-45Al-5Nb-0.3Y alloy is determinedas 1 200℃,0.01 s-1.The flow stresses are decreased by yttrium addition under the same compressive conditions.The activationenergies of deformation Q are calculated as 448.6 and 399.5 kJ/mol for Y-free and Y-containing alloys,respectively.The deformedmicrostructure observation under 1 200℃,0.01 s-1condition indicates that Ti-45Al-5Nb-0.3Y alloy shows more dynamicrecrystallization.The improvement of hot deformability of Ti-45Al-5Nb-0.3Y alloy induced by yttrium addition should be attributedto that the smaller the original lamellar colonies,the lower the deformation resistance and activation energy of deformation are,andthe more the dynamic recrystallization is.
The effects of 0.3% (molar fraction, the same below) yttrium addition on hot deformability of lamellar Ti-45Al-5Nb alloywere investigated by simulated isothermal forging tests. Ingots with the nominal compositions of Ti-45Al-5Nb and Ti-45Al-5Nb -0.3Y were prepared by induction skull melting. Simulated isothermal forging tests were conducted on Gleeble 1500Dthermo-simulation machine using a 6 mm in diameter and 10 mm in length compressive specimen at the deformation temperatures of 1 100,1 150,1 200 ° C and strain rates of 1.0, 0.1, 0.01 s-1. The results show that yttrium addition remarkably improves hotdeformability of Ti-45Al-5Nb alloy. An appropriate hot deformation processing parameter of Ti-45Al- 0.01 s-1. The flow stresses are decreased by yttrium addition under the same compressive conditions. The activationegies of deformation Q are calculated as 448.6 and 399.5 kJ / mol for Y-containing and y-containing alloys, respectively.The deformed microstructure observations ation under 1 200 ℃, 0.01 s-1condition indicates that Ti-45Al-5Nb-0.3Y alloy shows more dynamicrecrystallization. The improvement of hot deformability of Ti-45Al-5Nb-0.3Y alloy induced by ytriumtrium addition should be attributedto that smaller the original lamellar colonies, the lower the deformation resistance and activation energy of deformation are, and the more the dynamic recrystallization is.