重熔对(Al_2O_3+Al_3Zr)_p/A356复合材料组织及力学性能的影响

Effects of the Remelting Treatment on the Solidification Microstructure and Mechanical Properties of the In-situ Synthesized Composites in A356-ZrOCl_2 System

利用A356-ZrOCl2体系,通过熔体原位反应法制备了(Al2O3+Al3Zr)p/A356复合材料。X射线衍射仪(XRD)、扫描电镜(SEM)分析表明,A356-ZrOCl2体系原位合成的增强颗粒为Al3Zr和Al2O3,颗粒细小,且均匀分布在基体中;该复合材料经不同温度的重熔时,随着重熔温度的提高,重熔组织中内生颗粒的分布更均匀,形态趋于圆钝化,但温度过高会导致局部颗粒的粗化,最佳的重熔温度为850℃。同时,随着重熔次数的增加,颗粒变得更细小,分布更均匀,但过多次数的重熔导致了颗粒体积分数的减少,最佳的重熔次数为5次。拉伸试验结果表明,复合材料的抗拉强度随着重熔温度的提高以及重熔次数的增加而增大,但过高温度以及过多次数的重熔均导致了复合材料抗拉强度的下降。

In-situ (Al2O3+Al3Zr)p/A356 composites have been synthesized successfully by the direct melt reaction method in the A356-ZrOCl2 system. With the help of X-ray diffraction (XRD),scanning electron microscope (SEM), it is found that the formed Al3Zr and Al2O3 particles are fine and well distributed in the matrix. The distribution of in-situ particles in remelted microstructure becomes more homogeneous with the spheroidization of particles with the increase of remelting temperature, however, partial particles can be coarsened with the remelting temperature more than 850 ℃. The optimium remelting temperature is 850 ℃. Meanwhile, with the increase of remelting times, the particles become finer and finer with more homogeneous distribution, however, the volumetric fraction of the particles can be dropped as a result of excessive remelting times, so the optimized remelting times is 5. Tensile testing reveal that tensile strength of the composites is improved with increasing in remelting temperature and in remelting times, however, it is deteriorated with remelting temperature more than 850℃ and remelting times more than 5.