Zr和Ce对Ti-11Si亚共晶合金组织及压缩性能的影响

Effect of Zr and Ce on microstructure and compressive properties of Ti-Si hypoeutectic alloy

采用显微组织观察(OM)、X射线衍射(XRD)、扫描电镜(SEM)、能谱分析(EDS)以及压缩性能测试等手段,研究了元素Zr和Ce对Ti-11 at%Si铸态亚共晶合金组织和室温压缩性能的影响。结果表明,在Ti-Si亚共晶合金中添加8.0 at%的Zr可降低Si在α-Ti中的固溶度,促进硅化物细小、弥散析出,可改善合金的压缩强度和塑性。而添加0.5 at%的Ce可以明显细化α-Ti枝晶和共晶团组织,也可提高合金的压缩强度和塑性。且Ce对Ti-Si亚共晶合金的细晶强化效果比Zr要好。物相分析和EDS结果表明,Zr和Ce都主要存在于Ti5Si3相中,Zr则取代了部分Ti原子,形成了(Ti,Zr)5Si3相,Ce取代了部分Si原子,形成了三元硅化物Ti5(Si,Ce)3相。

The effect of Zr and Ce on microstructure and compressive properties at room temperature of as-cast Ti-11 at% Si hypoeutectic alloy was investigated by means of optical microscopy（OM）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,energy dispersive spectrometry（EDS） and compressive test.The results show that with proper addition of Zr（8.0 at%） to Ti-11 at% Si hypoeutectic alloy,the solid solubility of Si in α-Ti is reduced,which promotes the precipitation and refines the grains of silicides.Thus,the compressive strength and ductility of the alloy are improved.The sizes of α-Ti dendrites and eutectic colony of Ti-11 at% Si hypoeutectic alloy are evidently refined by minor addition of Ce element（0.5 at%）.The compressive strength and ductility of the alloy are also improved significantly.Compared to Zr element,rare earth Ce plays more prominent role in grain refining and the increase of the compressive strength and ductility of the studied alloy.Both Zr and Ce atoms distribute mostly in Ti5Si3 silicides.Zr atoms replace Ti atoms leading to the formation of（Ti,Zr）5Si3,whereas Ce atoms replace Si atoms resulting in the formation of ternary silicides Ti5（Si,Ce）3.