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采用过流冷却体式流变挤压成形工艺制备高铬铸铁半固态挤压件,对挤压件内部组织差异进行了分析。结果表明,由于凹模中熔体内部存在温度梯度,从而使制备的高铬铸铁半固态挤压件顶部、中部、底部组织存在明显的差异。顶部组织中部分先共晶枝晶状奥氏体或较粗大的杆状M7C3碳化物经过流冷却体时得以保留,受凸模激冷没有发生长大和相变。中部和底部的组织中枝晶状奥氏体或杆状M7C3碳化物经过流冷却体时发生蔷薇化、球化或折断、破碎、磨圆,因在凹模中凝固时间较长,先共晶相和剩余液相发生相变并有长大现象。比较而言,中部组织中先共晶相的转变产物或先共晶相较底部凝固时间更长,长大更明显。
High-chrome cast iron semi-solid extrusion was prepared by flow-through cooling and rheo-extrusion process, and the difference of the internal structure of the extrusion was analyzed. The results show that due to the temperature gradient inside the melt, the top, middle and bottom structures of the semi-solid extruded high chromium cast iron have obvious differences. Partially eutectic dendrite austenite or coarser rod-shaped M7C3 carbides in the apical tissue were retained during flow cooling and were not grown and transformed by the chilled mode. Dendrite austenite or rod-like M7C3 carbides in the middle and bottom tissues undergo roseification, spheroidization, or breakage, crushing, and rounding through the flow-cooling body. Due to the longer solidification time in the die, the first eutectic Phase and the remaining liquid phase change and growth phenomenon. In comparison, the transformation products of the first eutectic phase in the middle part of the microstructure or the eutectic phase are longer and grow more obviously than the bottom part.