Effect of Ultrasonic Surface Rolling Process Microstructure and Properties of Titanium Hydride Sintered Pure Titanium
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摘要: 采用超声表面滚压（USRP）技术对氢化钛烧结纯钛进行表面强化，并借助 X射线衍射(XRD)、电子背散射衍射(EBSD)、扫描电镜（SEM）和透射电子显微镜（TEM）分析滚压后纯钛的微观组织演化及性能影响。结果表明，滚压后组织呈梯度变化，最表面晶粒为等轴纳米晶，尺寸约100 nm，随表面距离增大，晶体组织依次为块状晶、层片状组织及等轴粗晶，塑性变形层厚度可达400 μm。滚压后表面硬度提高了36%，表面粗糙度显著降低，滚压后引发的晶粒细化和残余应力有助于产生致密的钝化膜，提高了耐腐蚀性能。此外滚压后抗拉强度和屈服强度为640 MPa、485 MPa，分别提高了32 %和27 %，但延伸率有所下降，断口形貌总体仍表现为韧性断裂。
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关键词:
Abstract: In this work, a titanium prepared by sintered titanium hydride was treated by ultrasonic surface rolling process (USRP), and effects of the plastic deformation on microstructure evolution and properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM).Results demonstrated that a gradient microstructure was produced by the USRP with the static load of 600 N, and the average thickness of the deformation layer was about 400 μm. In particular, the outermost layer of the deformed microstructure displayed an equiaxed nanocrystals, and the average grain size of the fine grains was about 100 nm. Improvement of surface roughness, grain refinement and high surface compressive residual stress caused by rolling synergistically help to form a dense and stable passive film on the deformation layer, which could improve the corrosion resistance effectively. In addition, taking advantages of the microstructure evolution, the ultimate tensile strength and yield strength were 640.57 MPa and 485.29 MPa, increased by 32.43 % and 27.57 % respectively. Meanwhile, the surface hardness was increased by 36% for the USRP treated titanium alloy.However, the introduction of deformation layer made a decrease of uniform elongation, while the fracture morphology indicated a ductile failure. -
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