纳米SiC颗粒增强镁基复合材料半固态搅拌法制备工艺优化

Process Optimization of Si C Nanoparticle Reinforced Magnesium Matrix Composites Prepared by Semi-solid Mechanical Stirring

采用半固态机械搅拌铸造法,制备了增强体平均粒径50 nm的Si C颗粒增强镁基复合材料(n-Si Cp/Mg9Al),分别对不同质量分数纳米颗粒、不同搅拌时间和不同搅拌温度时,复合材料的微观组织和力学性能进行了研究。结果表明,随着Si C含量的增加,合金基体组织先细化后又出现变粗的现象,适当延长搅拌时间能更有效地细化组织,在较低温度下搅拌可以更明显地细化复合材料的微观组织。合金抗拉强度随着Si C含量的增加先增加后降低,在Si C含量为1.5%时最好,为198 MPa。在含量为2%时又有所降低,但是高于不加Si C时。搅拌时间为15 min时,复合材料的屈服强度、抗拉强度较之基体分别提高了12.8%、22%,断后伸长率由基体合金的2%提升到4%。继续延长搅拌时间到30 min,材料的室温拉伸性能出现明显恶化。不同搅拌温度下Si Cp/Mg9Al纳米复合材料与铸态Mg9Al合金相比其室温拉伸性能有明显提高,搅拌温度为600℃的Si Cp/Mg9Al纳米复合材料的室温拉伸性能最好,其屈服强度、抗拉强度和断后伸长率分别为106 MPa、155 MPa和4%。

The semi-solid mechanical stir casting technology was used to fibricate Mg-matrix composites reinforced by Si C nanoparticle particle with an average size of 50 nm, i.e. n-Si CP/Mg9 Al. The microstructure and mechanical properties of the composites with different mass fraction of nanoparticle Si CPat different stirring time and different stirring temperature were studied. The results show that, with the increase of the Si C content, the matrix alloy is refined and then coarsened.Extending the stirring time appropriately can refine the structure more effectively, when stirring 15 min, the grain size is finest. When stirring at a lower temperature（600 ℃）, the grain refinement effect is more obvious. Tensile strength of the composite increases at first then reduce with the increase of Si C content, it＇s best when Si C content is 1.5%, and the tensile strength is 198 MPa. The yield strength, tensile strength of the composite stirred for 15 min is increased by 12.8% and 22%compared with matrix, respectively, the elongation to fracture increase from 2% to 4%. Continuing to extend the stirring time to 30 min, room temperature tensile properties become worse significantly. The room temperature tensile properties of Si Cp/Mg9 Al nanocomposite stirred at different temperature obviously enhance compared with as-cast Mg9 Al alloy, the Si Cp/Mg9 Al nanocomposite stirred at 600 ℃ behave best, its yield strength, tensile strength and elongation to fracture are106 MPa, 155 MPa and 4%, respectively.