冷轧预处理对TC4合金540 ℃渗氮组织的影响

TC4钛合金经820 ℃固溶处理及室温下冷轧得到10%、20%、30%、40%、50%不同变形量的试样,之后在540 ℃进行渗氮复合时效处理8 h。利用光学显微镜、X射线衍射仪、扫描电镜等分析了不同变形量下合金渗氮组织和时效组织的变化特点以及渗氮试样表面的相结构和形貌的变化。试验结果显示,渗氮处理后,试样表面生成了TiN、Ti₂N等高硬的氮化物颗粒,变形量越大,试样表面生成的氮化物颗粒越多且尺寸越大;经固溶处理后,TC4合金的室温组织为α相+亚稳β相,经渗氮复合时效处理后,亚稳β相分解为α相,同时α相向β相转化,变形量越大,析出的β相越多,且这种趋势不如单纯的时效处理明显。

Effect of cold rolling pretreatment on microstructure of TC4 alloy nitrided at 540 ℃

TC4 titanium alloy was solution treated at 820 ℃ and cold rolled at room temperature to obtain specimens with different deformation of 10%, 20%, 30%, 40%, 50%, and then nitrided and aged simultaneously at 540 ℃ for 8 h. The change of nitrided microstructure and aged microstructure with different deformation amounts and the change of phase structure and morphology of the nitrided specimen surface were analyzed by means of metallographic microscope, X-ray diffractometer, scanning electron microscope (SEM). The results show that after nitriding treatment, high-hardness nitride particles such as TiN and Ti₂N are formed on the surface of TC4 alloy, and the larger the amount of deformation, the more nitride particles with larger size are formed on the specimen surface. After solution treatment, the microstructure of the TC4 alloy is α phase+metastable β phase. After nitriding, the metastable β phase decomposes into α phase, while α phase transforms into β phase, and the larger the amount of deformation, the more β phase precipitates, but this phenomenon is not as obvious as that only aged.