Thixoforming and Rheo-Die-Casting of A356/SiC Composite
Thixoforming and Rheo-Die-Casting of A356/SiC Composite
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DOI：
10.3390/met10020251
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发表时间：
2020-02
期刊：
影响因子：
2.9
通讯作者：
Sukangkana Talangkun;Charinrat Potisawang;Phuriphut Saenpong
中科院分区：
文献类型：
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作者：
Sukangkana Talangkun;Charinrat Potisawang;Phuriphut Saenpong
本研究对流变压铸工艺及触变成形制备A356/碳化硅复合材料进行了研究。该复合材料含有15%的尺寸约为15-37微米的碳化硅颗粒作为增强相。采用半固态搅拌铸造的方法制备复合喂料，将经过处理的碳化硅粉末逐步加入到A356合金熔体中，形成连续搅拌的浆料复合熔体，然后在钢模中浇注。对于触变成形，原料被重新加热到583℃(约0.4分液体)，其粘度随着剪切速率的降低而降低，这意味着A356/SiC表现出剪切变稀或非牛顿行为。这是由获得的具有相对球状颗粒的特征坯料结构引起的，该颗粒适应半固体复合材料的流动。在流变压铸工艺中，A356/SiC原料在压铸前在610-615°C(约0.8-0.9分液体)下重新熔化，所得浆料分别以3和4m/S的注射速度和11和12 Mpa的压力注入模具。一次生产两个16×15.6×205mm3的试件，T6固溶处理540℃1h，淬火，135℃时效12h，结果表明，低速和低压流变型压铸样品在零件末端呈现不均匀的充填，而高压和高速都促进了碳化硅颗粒在整个零件长度上的均匀分布。在流变压铸条件下，在4m/S速度和12 MPa压力下制备的样品获得的组织和硬度最均匀。
This research investigated the rheo-die-casting process and the production of an A356/silicon carbide (SiC) composite by a thixoforming. The composite contained 15 percent by weight SiC particles of around 15–37 µm in size as the reinforcing phase. The composite feedstock was produced by semi-solid stir-casting, where pretreated SiC powder was gradually added into the A356 alloy melt to form a continuously stirred slurry composite melt, which was then cast in a steel mold. For thixoforming, the feedstock was reheated to 583 °C (approximately 0.4 fraction liquid), and its viscosity was reduced with shear rate, implying that A356/SiC exhibits shear thinning or non-Newtonian behavior. This is caused by the characteristic billet structure obtained having relatively globular grains that accommodate the flow of the semisolid composite. In the rheo-die-casting process, the A356/SiC feedstock was re-melted at 610–615 °C (approximately 0.8–0.9 fraction liquid) prior to die-casting and the resulting slurry was injected into a die with injection speeds of 3 and 4 m/s and pressures of 11 and 12 MPa, respectively. Two work-pieces of 16 × 15.6 × 205 mm3 were produced in one shot, and the resulting samples were subjected to T6 solution treatment at 540 °C for 1 h, quenched, and aged at 135 °C for 12 h. The results show that both low speed and low pressure rheo-die-cast samples exhibit uneven filling at the end of the part, whilst both high pressure and high speed promote more uniform distribution of SiC particles throughout the part length. In the as-rheo-die-cast condition, the most uniform of microstructures and hardness obtained from a sample fabricated at 4 m/s speed and 12 MPa pressure.