Influence of Heat Treatment on Microstructure and Tensile Property of In-situ TiB/Ti-55531 Composite Forging Stocks
The effects of heat treatment parameters such as solution and aging temperature on the microstructures and tensile properties of in-situ 2vol%TiB/Ti-55531 composite forging stocks were studied,which were obtained by vacuum consumable arc melting and near-isothermal thermal-plastic deformation.The results show that,after 2vol%TiB/Ti-55531 composites and its matrix alloy solid heat treatment,the size and morphology of TiB enhanced phases change little after solid solution heat treatment,and the fine acicular α phase dispersed in the β phase matrix re-dissolve mostly,while the fine acicular α phase at grain boundary and local preferred orientation grow into the rod-like primary α phase,which result in the plasticity of materials increases and the strength decreases.After the solid-soluble state Ti-55531 matrix and its composite are subjected to timely heat treatment,the rod-like primary α phases are continuously coarsened,and the fine needle-like secondary α phases are precipitated,which obviously optimize the comprehensive mechanical properties of solution treatment composites and its matrix alloy.As the solution temperature increase from α+β to β region,the rod-like primary α phases disappear basically in the solution aging microstructure,and the number of fine needle-like secondary α phase increases obviously,resulting in the strength of materials increases and the plasticity decreases.With the increase of aging temperature,the rod-like primary α phases distribute along grain boundary in the microstructure of the composite and its matrix alloy have little change,while the fine needle-like secondary α phase distribute in the matrix of β phase coarsens,which reduces the strength of materials and increases its plasticity.
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