Ti-10V-2Fe-3Al合金的结构稳定性、微观组织及力学行为

Structural stability,microstructure and mechanical behavior of Ti-10V-2Fe-3Al alloy

采用真空自耗熔炼及锻造方法制备Ti-10V-2Fe-3Al(Ti-1023)合金,利用X射线衍射、透射电子显微观察和力学性能测试等研究合金的结构稳定性以及冷轧变形合金的微观组织演变及力学行为。结果表明,Ti-1023合金的结构稳定性、微观组织和力学行为与冷轧变形及热处理密切相关。无论是单相区(833℃)固溶后水冷还是两相区(753℃)固溶后水冷,合金的应力-应变曲线均呈现"双屈服"特征。这表明单相区或两相区固溶水冷后的β相均呈现较低的结构稳定性,在应力作用下产生应力诱发α"马氏体相变,从而导致合金的"双屈服"行为。剧烈冷轧变形和应力/应变诱发α"马氏体相变均可使β相晶粒细化,同时也伴随马氏体进一步细化。由于冷轧变形引入的大量位错、晶界和相界等缺陷可作为α相的形核位置,冷轧态Ti-1023合金经550℃短时时效即可析出大量细小的α相,合金因此呈现良好的强度和塑性匹配。

In the present study,Ti-10V-2Fe-3Al(Ti-1023)alloy was prepared by vacuum consumable melting and forging technique.The structural stability,microstructural evolution and mechanical behavior of the alloy were systematically investigated by X-ray diffraction,transmitting electron microscopy and mechanical testing.It is indicated that the structural stability,microstructure and mechanical behavior of Ti-1023 alloy are closely related to the cold deformation and heat treatment.Regardless of the solution treatments in singleβphase region(833℃)orα+βphase region(753℃),double yielding occurs in the stress-strain curves of the alloy.This suggests that theβphases in the alloys with above solution treatments possess low structural stability,and stress inducesβ→α"martensitic transformation,leading to double yielding behavior.Severe cold rolling deformation and stress/strain induced martensitic transformation gives rise to the refinement ofβgrains and martensite variants.Since numerous dislocations and grain/phase boundaries induced by severe cold deformation can be used as nucleating sites for the precipitation ofαphase,a large amount of fineαphase is precipitated out of the cold rolled Ti-1023 alloy after short aging at 550℃,therefore,the alloy exhibits a good balance between strength and ductility.