Study on Microstructure Evolution and Microhardness of Ti2AlNb-Based Alloy in Gradient Extrusion Process
The effects of gradient extrusion on evolution of the grain orientation,grain size,and grain boundary orientation difference and mechanical properties of Ti2AlNb-based alloy were studied by EBSD combined with microhardness test.The results show that preferred orientation<101>in the microstructure of Ti2AlNb-based alloy gradually disappears after the gradient extrusion deformation,the grain size is gra-diently distributed,and the structure of fine grains on the surface and coarse grains in the core is formed.The average grain size in the edge region decreases from the initial 20.64 μm to 3.92 μm,and the average grain size in the core region decreases to 11.24 μm after gradient extrusion from two forming units.At the same time,the length of high-angle grain boundary in the edge region gradually increases from the initial 11 166.5 μm to 34 905.8 μm.The microhardness of the deformed sample shows an increasing gradient dis-tribution from the core to the edge,and the average microhardness values of the first gradient and the se-cond gradient increase by 9.9%and 11.5%respectively,compared with the initial sample.It provides theo-retical support for the study of the large plastic deformation process of high temperature titanium alloy.
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