铜模喷铸对钐铁合金组织形貌及物相组成的影响

Effect of Copper Mold Spray Casting on Microstructure and Phase Composition of Sm-Fe Alloy

采用铜模喷铸技术制备钐铁合金快速凝固试样,利用薄材的非稳态导热方程计算钐铁合金在铜模内的冷却速率。借助光学显微镜、扫描电镜、能谱仪、X射线衍射仪及X射线光电子能谱仪研究了钐铁合金在氮气喷铸后快速凝固过程中的组织形貌及物相组成变化。结果表明,氮气将熔融态Sm-Fe合金喷铸到铜模内后,合金的冷却速度约为16.8 K/s;较大的冷却速率使枝晶间距明显变小,促进了合金晶粒细化,并抑制各相之间的相互扩散,合金成分更加均匀;氮化反应基本上只在喷铸试样表面进行,且生成物主要由Sm2Fe17Nx与氮的氢氧化物构成,相对含量分别为34.36%与65.64%。

The rapid solidification samples of Sm-Fe alloy were prepared by copper mold spray casting.The cooling rate of Sm-Fe alloy in copper mold was calculated by the unsteady heat conduction equation of thin material.The changes of microstructure and phase of Sm-Fe alloy during rapid solidification after nitrogen spray casting were studied by means of optical microscope,scanning electron microscope,energy spectrometer,X-ray diffractometer and X-ray photoelectron spectrometer.The results show that the cooling rate of molten Sm-Fe alloy is about 16.8 K/s after it is sprayed into the copper mold by nitrogen gas.The relatively large cooling rate makes the dendrite spacing obviously decreased,promotes grain refinement of the alloy,and restrains interdiffusion of the phases,resulting in more homogeneous composition of the alloy.The nitridation reaction is basically carried out only on the surface of the casting sample,and the products are mainly Sm2Fe17Nx and nitrogen hydroxides with relative contents of 34.36% and 65.64%,respectively.