粉末冶金50％Sip／6061Al复合材料的结构与性能

Microstructures and properties of 50%Si_p/6061Al composites fabricated by powder metallurgy

以Si粉和6061Al合金粉末为原料,采用机械球磨-常压烧结工艺制备硅颗粒含量(质量分数)为50%的颗粒增强铝基复合材料,利用扫描电镜和X射线衍射仪分析不同温度下烧结的复合材料结构与物相组成,并测试材料的密度、抗弯强度、硬度及热膨胀系数等性能。结果表明,通过球磨可获得成分均匀的Si_p/6061Al复合粉体。烧结温度为700℃时,50%Si_p/6061Al复合材料仅含少量Al_2O_3杂质,Si相分布均匀,呈半连续骨架结构,Si颗粒与6061Al基体合金结合良好,材料中孔隙的数量和尺寸都最小。在680~750℃温度范围内,随烧结温度升高,50%Si_p/Al复合材料的致密度及抗弯强度先增大后降低,在700℃烧结的50%Si_p/6061Al复合材料具有优异的综合性能,其致密度、抗弯强度、硬度(HB)、热膨胀系数(室温)分别为96.4%,310.8 MPa,225.4和7.43×10^(-6)/K。

50%Sip/6061Al composites were fabricated by a powder metallurgy technique via mechanical ball milling and pressureless sintering using Si and 6061Al powders as raw materials. Microstructures and phase composition were analyzed by scanning electronic microscope （SEM） and X-ray diffraction （XRD）. Density, bending strength, hardness and coefficient of thermal expansion （CTE） at room temperature （RT） of the composites were also detected. The results show that the mechanical ball milling is beneficial to form the homogeneous Sip/6061Al composite powder. When the sintering temperature is 700 ℃, the sintered 50%Sip/6061Al composites have a high purity. Only a little bit Al2O3 impurities are contained, and the Si phase distributes in the composite uniformly with a semi-continuous skeleton-like structure and combines well with the Al alloy matrix, in which the number and size of pores are the minimum. With increasing the sintering temperature from 680 ℃ to 750 ℃, the relative density and bending strength of the composites increase initially and then decrease. The Sip/6061Al composites sintered at 700 ℃ have the optimal properties： relative density of 96.4%, bending strength of 310.8 MPa, Brinell hardness of liB 225.4 and CTE （RT） of 7.43 × 10-6/K.