Study On Hot Deformation Behavior Of Zr₉₂Ti₈ Alloy

The development of Aeronautic and Astronautics has led to the studies of new aeronautic materials to zirconium alloys which have the similar properties of titanium alloys.The history of development of Zr alloys can claim to be the process of optimizing their composition and processing technology.Ti and Zr can form continuous infinite solid solutions and the components of Zr-Ti have shown great potential in the design of biomedical alloys and zirconium alloys with high strength and toughness.A new Zr₉₂Ti₈binary alloy had been development for broadening the alloy system of Zr alloys and their application in non-nuclear field.The hot deformation behavior of as cast Zr₉₂Ti₈ alloy in single beta phase field had been investigated.The constitutive models and hot processing maps of Zr₉₂Ti₈ alloy in the single beta phase field had been built based on the results of experimental flow stress.The flow curves of Zr₉₂Ti₈ showed obvious flow softening behavior during hot deformation in single beta phase field,which mainly affected by the strain rate.The hyperbolic sine constitutive model of Zr₉₂Ti₈ alloy in the single beta phase field was established and modified by the true strain,and the activation energy of hot deformation which corresponding the peak stress is 281.5 kJ/mol.In the strain range of 0.1-0.7,the activation energy of hot deformation of Zr₉₂Ti₈ binary alloy decreased rapidly with the increasing strain at the very beginning and then decreased slowly with the increasing strain in the range of 195.0-252.2 kJ/mol.All the activation energies of hot deformation of Zr₉₂Ti₈alloy were determined to be higher than the self-diffusion activation energy of beta Zr and beta Ti.The BP network model which showed better predictive performance than the strain-modified constitutive equation was also established for modeling the flow stress of Zr₉₂Ti₈alloy during the hot deformation in single beta phase field.The instability region of hot processing maps of Zr₉₂Ti₈ binary alloy in single beta phase increased with the increasing strain.The hot processing maps revealed that the Zr₉₂Ti₈binary alloy had two theoretical optimal domains,one is the deformation temperature range of 825-893?and the strain rates range of 0.001-0.0033 s^-1,another is the deformation temperature range of 955-1025?and strain rates range of 0.001-0.0033s^-1.The hot deformation mechanisms of Zr₉₂Ti₈ alloy in the single beta phase field were flow localization,dynamic recovery and dynamic recrystallization.Dynamic recrystallization of Zr₉₂Ti₈ alloy was difficult to occur during the hot deformation due to he coarse initial grains.