热处理对SiC增强YL117复合材料组织和性能影响

Effect of Heat Treatment on Microstructure and Properties of SiC Reinforced YL117 Composites

用球磨的方法制备弥散分布的SiC-Al粉体,然后热压成预制块,通过预制块的重熔稀释,在半固态的情况下搅拌铸造制备SiC增强YL117复合材料。研究了SiC体积分数为3.5%、4.5%和5.5%时,YL117基复合材料的微观组织和力学性能,并对力学性能最好的4.5%SiC/YL117复合材料进行T6热处理,确定优化的固溶和时效工艺。结果表明:SiC体积分数为4.5%时,SiC弥散分布,二次相细小,显微硬度(维氏硬度)达到最大值144.0,比基体合金提高了21.7%,拉伸强度和伸长率达到最大值272.5 MPa和2.05%,分别提高23.1%,120.4%;当SiC体积分数为5.5%时,在基体内部出现了团聚现象,导致力学性能下降。实验确定的优化的热处理工艺为500℃×4h固溶,170℃×10h时效。经热处理后的4.5%SiC/YL117复合材料显微硬度(维氏硬度)达到164.3,比基体合金提高38.9%;拉伸强度达到295.4 MPa,比基体合金提高33.4%;伸长率达2.12%,提高了128.0%.

The dispersed SiC-Al powders were prepared by ball milling method and then hot pressed into the prefabricated block,and SiC reinforced YL117 composites were fabricated by semi-solid stirring casting.The microstructure and mechanical properties of YL117 matrix composites were investigated,where the volume fraction of SiC was 3.5%,4.5% and 5.5%,separately.Subsequently,the 4.5%SiC/YL117 composites with the best mechanical properties were treated by T6 treatment,and optimal solid solution treatment and aging process were obtained.The results show that in case that the volume fraction of SiC was 4.5%the composites presented an uniform distribution of SiC and small size of second phase,the maximum tension strength and elongation,272.5 MPa and 2.05%,increased by 23.1% and 120.4% with respect to those of matrix alloy,respectively.The agglomeration occured in the matrix when the volume fraction of SiC was 5.5%,which resulted in the decrease of mechanical properties.The optimal heat treatment process was experimentally determined as 500 ℃×4 hsolid solution followed by 170 ℃×10 haging.The microhardness of 4.5%SiC/YL117 composites after heat treatment reached 164.3 HV,increased by 38.9% with respect to that of matrix alloy,tensile strength and elongation,295.4 MPa and 2.12%,were improved by 33.4% and 128.0%,respectively.