α相含量及形态对TC4钛合金组织和力学性能的影响

Effects of content and morphology of α phase on microstructure and mechanical properties of TC4 alloy

利用扫描电镜、透射电镜、X射线衍射仪、拉伸试验机以及硬度计等研究了多重热处理TC4钛合金获得不同α相的含量和形态对其组织和力学性能的影响。结果表明:采用三重热处理工艺能有效调节TC4钛合金组织次生α相的含量和形态,从而优化试验合金的力学性能。第一重热处理温度越高,初生等轴α相含量越低且减少速率越快。第二重热处理温度越高,组织中等轴α相的数量不断减少,次生条状α相含量增多且形态更为粗大,且组织中出现二次次生α相。随着初生等轴α相数量增加,晶粒尺寸减小,次生α相长宽比降低,集束域方向越混乱,试验合金的抗拉强度越高,塑性也越好。次生α相的含量越多,试验合金的硬度越高。经过940℃×1 h(WQ)+880℃×1 h(WQ)+820℃×1.5 h(AC)热处理后,试验合金具有等轴组织,表现出最好的强塑性匹配;而采用940℃×1 h(WQ)+920℃×1 h(WQ)+820℃×1.5 h(AC)热处理试验合金具有双态组织,表现出最高的硬度,且其强塑性匹配较好。

Effects of the content and morphology ofαphase obtained by multiple heat treatments on the microstructure and mechanical properties of TC4 alloy were studied by using electron scanning microscopy,transmission electron microscopy,X-ray diffraction,tensile testing machine and hardness tester.The results show that triple heat treatments can adjust effectively the content and morphology ofαphase,so that optimize the mechanical properties of the TC4 alloy.The higher the temperature of the first heat treatment is,the lower the content of primary equiaxialαphase and the faster the decreasing rate.The higher the temperature of the second heat treatment is,the content of the equiaxialαphase in the microstructure decreases continuously,while the content of banded secondaryαphase increases and its morphology is more coarse,and second secondaryαphase appears.As the content of primary equiaxialαphase increases,the grain size and aspect ratio of secondaryαphase decrease,and the directions of cluster domains are more disordered,both the tensile strength and the plasticity of the tested alloy are higher.In addition,the higher the content of secondaryαphase is,the higher the hardness of the test TC4 alloy.After heat treatment at 940℃×1 h(WQ)+880℃×1 h(WQ)+820℃×1.5 h(AC),the tested TC4 alloy has equiaxial microstructure and shows the best strength-plasticity matching.While after heat treatment at 940℃×1 h(WQ)+920℃×1 h(WQ)+820℃×1.5 h(AC),the tested TC4 alloy has duplex microstructure and the highest hardness,as well as relatively good strength-plasticity matching.