铜模喷铸Cu-Zr合金非平衡凝固组织演变行为

采用真空感应熔炼与铜模喷铸相结合,制备出不同成分的Cu_(100-x)Zr_x(x=5,30,50)合金。利用光学显微镜、扫描电镜、能谱分析及X射线衍射技术,对比研究了快冷合金的晶粒形貌、元素分布、相组成及类型等组织演化规律。结合差热分析技术研究了合金实时凝固过程。结果表明,随Zr含量增加,非平衡凝固Cu-Zr合金中初生相体积分数不断提高,分别呈现非小平面→小平面→非小平面的转变。由于铜模激冷效应,Cu_(70)Zr_(30)合金中Cu_(51)Zr_(14)+L→Cu_8Zr_3包晶转变与Cu_(50)Zr_(50)合金中CuZr→Cu_(10)Zr_7+CuZr_2共析转变均受到抑制。热分析曲线中未出现包晶相变峰和共析相变峰,合理解释了Cu-Zr合金非平衡组织的形成。

Microstructure evolution of non-equilibrium solidified Cu-Zr alloy by spray casting

Non-equilibrium solidified Cu100-xZrx(x=5, 30, 50) alloys with different compositions were prepared by vacuum induction melting and spray casting method. The microstructure evolution including grain morphology, element distribution and phase components of non-equilibrium solidified alloy was presented by optical microscope, scanning electron microscope, energy spectrum analysis and X ray diffraction technique. The solidification process of the alloys was studied by differential scanning calorimetry. The results show that the volume fraction of primary phase increases continuously with the increase of Zr content and reveals a transition from non-faceted to faceted and finally non-faceted phase. Affected by the fast cooling effect of copper mould, both the peritectic transformation in Cu70Zr30 alloy and eutectoid transformation in Cu50Zr50 alloy are suppressed, which are further verified by the thermal analysis curve under slow cooling condition. Consequently, the formation regularity of non-equilibrium microstructure of spray casted Cu-Zr alloy can be well explained.