硅含量对喷射成形铝硅复合材料显微组织与力学性能的影响

利用双喷嘴扫描喷射成形技术制备27%SiAl、42%SiAl、50%SiAl等3种Si-Al合金电子封装材料,并对该材料进行热等静压致密化处理。研究合金沉积态和热等静压态的显微组织,测定合金的热膨胀系数、抗拉强度及抗弯强度,利用扫描电镜研究其断裂机制。结果表明:沉积态Si-Al合金的硅相呈均匀弥散分布。随含硅量增加,合金凝固区间增大,初生硅相的数量增多,平均尺寸增大,由全部颗粒状分布逐渐演化为呈部分颗粒、部分骨架状分布,这种均匀弥散分布的结构有利于降低合金的热膨胀系数。27%SiAl、42%SiAl、50%SiAl合金的热膨胀系数连续可控,室温至200℃分别为14.76×10 6、9.75×10 6、9.29×10 6/K。随硅含量升高,材料的抗弯强度和抗拉强度呈下降趋势。27%SiAl合金的平均抗拉强度和抗弯强度分别达到196 MPa和278 MPa,伸长率为9.5%。42%SiAl与50%SiAl的平均抗拉强度与抗弯强度都接近,分别达到140 MPa及220 MPa,伸长率小于1%。断裂方式由以铝相的韧性断裂为主逐渐转变为以硅相的脆性裂为主。

Effect of Si content on microstructure and properties of Al-Si metal matrix composite prepared by spray forming

Three different Si contents of 27%,42% and 50%(mass fraction) Si-Al alloys were prepared by double-nozzle scanning spray forming and hot isostatic pressing technology.The microstructure and fracture surface of the alloys were investigated by scanning electron microscopy and metallographic microscopy.The effect of Si content on thermal expansion coefficient and the ultimate flexural strength were studied.The results show that the as-deposited billet has an equiaxed and homogeneous structure.The solidification range,number of primary Si phase and the silicon crystal size of the Si-Al alloy increase with increasing Si content.The Si phase distribution status in alloy changes from particle to partly particle and partly framework,which is beneficial to the decrease of thermal expansion coefficient.The coefficient of thermal expansion of Si-Al alloy can be controlled continuously.The coefficients of thermal expansion of 27%SiAl,42%SiAl and 50%SiAl alloys are 14.76×10 6,9.75×10 6 and 9.29×10 6/K from room temperature to 200 ℃.The bending strength and the tensile strength decrease with increasing Si content.The bending strength,tensile strength and elongation rate of the 27%SiAl alloy are 196 MPa,278 MPa and 9.5%,respectively.The bending strength and tensile strength of the 42%SiAl and 50%SiA alloy are almost the same,which are 140 MPa and 220 MPa,the elongation rate of them is less than 1%.The fracture mechanism transforms from ductile fracture mode to brittle fracture mode with increasing Si content.