热处理对Ti-6Al-2.5V-1.5Fe-0.15O合金组织及力学性能的影响

Effect of heat treatment on microstructure and mechanical property of Ti-6Al-2.5V-1.5Fe-0.15O alloy

以真空非自耗电弧炉制备的低成本Ti-6Al-2.5V-1.5Fe-0.15O合金为对象,研究了不同冷却速率下固溶及时效温度对合金组织及性能的影响,发现固溶温度主要影响初生α相的含量.固溶冷却方式影响α的类型.单相区固溶时,初生α相消失,β晶粒内出现α片层集束,固溶淬火组织主要由残余未转变的β相以及针状的α';随着固溶温度的升高,针状马氏体α'相增多;两相区固溶后,时效组织均有固溶时产生的α相、时效α相以及残留的β相.时效温度较低时,α相形核能较低,元素扩散困难,需借助过饱和β相析出弥散相形核,因而针状α相细小而弥散;时效温度升高,α相形核以及长大驱动力大,时效α相易长大变粗.经固溶时效处理,合金强度随着温度升高先小幅升高后显著降低,塑性先增大后因晶界粗化以及粗片状α集束而降低.

The effect of solid solution temperature and aging temperature in different cooling rates on microstructure and mechanical properties of Ti-6Al-2.5V-1.5Fe-0.15 O alloy prepared by vacuum non-consumable arc melting process was studied. It was found that solid solution temperature mainly affects the content of primary α,and the type of solid solution cooling method has important effect on the type of primary α. Aging temperature will change the morphology of aging α phase. When the single phase zone is in solid solution,primary α phase disappears. The structure of the alloy after solid solution quenching is mainly composed of the residual phase and the needle like α＇. With the increase of solid solution temperature,the needle like α＇ increases. After solid solution in the two phase region,α phase,aging αphase and residual β phase all exist. At lower aging temperature,nuclear power and element diffusion α phase is lower.By means of saturated β phase precipitated nucleation,acicular α phase is fine and dispersive. With increase of aging temperature,nucleation energy of α phase is larger. Aging phase is easy to grow up. After solution-aging treatment,the strength of the alloy increases slightly firstly and then decreases with increase of temperature. Plasticity firstly increases and then decreases due to grain boundary coarsening and coarse lamellar α cluster.