Ti-60Ta合金快速凝固过程中的相变研究

Research on Phase Transformation of Ti-60Ta Alloy During Rapid Solidification

采用真空自耗电弧熔炼和热锻技术制备出Ti-60Ta合金棒,用等离子旋转电极(PREP)制粉技术制备出其球形粉末,并对棒材取块样进行高温淬火处理。利用SEM、XRD、TEM、DSC等分析手段对Ti-60Ta合金在快速凝固过程中的相变行为进行了研究。结果表明,Ti-60Ta原始块样和Ti-60Ta合金粉末相组成主要以bcc结构的β相为主;粉末粒径越小,快速凝固过程中冷却速率越高,α"马氏体相越多,β相越少;原始块样经过1000℃/60 min保温、淬火处理,生成了少量α"马氏体相;TEM像和选区电子衍射花样分析表明,在冷却速率更高的Ti-60Ta合金粉末中观察到板条状α"马氏体,宽度大约为50 nm,α"马氏体相优先生成于晶界处。

The Ti-60Ta alloy bars were prepared by vacuum arc smelting and then hot forging process.The bulk samples of Ti-60Ta alloy were cut from the bars,and some of them were quenched in the water.The spherical powders of Ti-60Ta alloy were prepared by plasma rotating electrode process(PREP).The microstructure and phase transition process were characterized by SEM,XRD,TEM,DSC and so on.It is revealed that both of the bulk samples and powders are mainly composed ofβ-Ti with bcc structure.With the decrease of powder size,the cooling rate increases during the rapid solidification process,and theα"martensite phase content increases while theβ-Ti content decreases.The bulk samples were kept at 1000℃for 60 min and then quenched in the water,resulting in a small amount ofα"martensite phase.The results of TEM and SAED reveal that the lathα"martensite phase with a width of 50 nm forms in the powders after rapid solidification,and theα"martensite phase mainly precipitates at grain boundaries.