Ti-6Al-4V titanium alloy was fabricated by a selective laser melting（SLM） technology, and annealed by heating at 800 ℃,850 ℃and 900 ℃ for 6 h followed by air cooling, respectively. The alloy was tested for microstructure, hardness, mechanical properties, fracture patterns of tensile and Charpy impact specimens. The results indicated that（a） martensite converted to a lamellar structure consisting of α and β phases in the Ti-6Al-4V alloy annealed at different temperatures;（b） the Ti-6Al-4V alloy annealed at 800 ℃ possessed the best mechanical properties compared with the Ti-6Al-4V ally annealed at other two temperatures, tensile strength being 1 029 MPa, yield strength being 928 MPa, and elongation being 12%;（c） the Ti-6Al-4V alloy annealed at different temperatures all exhibited about 16% decrease in strengths, about 42% increase in elongation, and about 50% increase in impact toughness compared to the Ti-6Al-4V alloy not annealed; and（d）the annealing temperature adaptable to Ti-6Al-4V titanium alloy formed by selective laser melting technology was 800 ℃.
采用淬火相变热膨胀仪测定了30MnNiCuMoB-RE铸钢890℃完全奥氏体化后以不同速度连续冷却时的膨胀曲线.通过金相检验和硬度测定研究了30MnNiCuMoB-RE铸钢在连续冷却过程中的相变动力学.结果表明:30MnNiCuMoB-RE铸钢在 890℃完全奥氏体化后以 0.01～100℃/s的速率冷却时,随着冷却速率的增大,奥氏体依次转变为铁素体、贝氏体和马氏体,铁素体转变温度区间为717～611℃,贝氏体转变温度区间为590～323℃,马氏体转变温度区间为313～168℃;从获得的连续冷却转变(CCT)曲线可知,随着冷却速率的降低,发生贝氏体相变的临界冷速为 50℃/s,发生铁素体转变的临界冷速为0.5℃/s;由于钢中存在一定程度的偏析,以 0.01～0.2℃/s的速率冷却时,奥氏体依次转变为铁素体和贝氏体,钢的组织不均匀;随着冷却速率的提高,钢的硬度从 200 HV10 提高至500 HV10.
20CrMnTi钢电机轴碳氮共渗和淬火后,表面硬度、心部硬度和有效硬化层深度均符合要求,但因内花键部位厚度不均匀,齿棒间距过大.在电机轴内花键薄壁部位增加一个套圈后热处理,内花键齿棒间距达到了要求.
输出轴是电动机、内燃机的重要零件.通过化学成分调整,制定合理的开坯、镦粗、精整等锻造工艺和调质处理工艺,试制成了 34CrNi3MoA钢输出轴锻件,其显微组织及拉伸、冲击性能均达到了设计技术要求.
