固溶时效过程中高导热Al-9Si合金组织性能演变

Evolution of Microstructure and Properties of High Thermal Conductivity Al-Si Alloys during Solution and Aging Treatment

采用水冷铜模制备高导热Al-9Si-Mg-Cu合金铸态试样,经固溶、时效处理后,分析了合金在不同状态下的显微组织、析出相形貌和分布、合金的硬度及导热性能,研究了固溶时效过程中合金的组织演变。结果表明,铸态下合金主要由初生α-Al、共晶Si相、Mg2Si相以及富Fe相组成;经过固溶和时效处理后,合金物相组成与铸态保持一致,但析出相显微组织形貌和分布明显发生变化;在固溶过程中,共晶Si相明显细化,时效处理后分布更为均匀,而Mg2Si和AlSiMgFe及AlSiMgCu相在时效处理后尺寸细小、分布均匀;固溶时效处理对析出相形貌、尺寸和分布均产生影响,将减少自由电子传输过程中的散射中心数量,降低散射几率,构建更有利于自由电子传输的通道,从而实现合金力学性能和导热性能的同时优化;最终,制备合金的显微硬度(HV)达到122.92,热导率达到162.73W/(m·K)。

High thermal conductivity Al-Si-Mg-Cu alloys were prepared by water-cooled copper mold.The microstructure,morphology and distribution of precipitated phases,hardness and thermal conductivity of the alloy were analyzed after solution and aging treatment.The evolution of microstructure and properties of the alloy during solution and aging treatment were analyzed.The results reveal that the alloy is mainly composed of primaryα-Al,eutectic Si phase,Mg2Si phase and iron-rich phases under as-cast state.After solution and aging treatment,the alloy phase composition presents the absence of change,however,morphology and distribution of precipitates change obviously.The eutectic Si phase is obviously spheroidized during the solution process with more uniform distribution after aging treatment,while Mg2Si and iron-rich phases have the smaller size and more uniform distribution after aging treatment.The solution and aging treatment have impact on morphology,size and distribution of the precipitated phase,which would reduce the probability of scattering during free electron transport,and build more channels for free electron transport in order to achieve the simultaneous optimization of the mechanical properties and thermal conductivity.Finally,the micro-hardness and the thermal conductivity of the alloy prepared reach 122.92 HV and 162.73 W/(m·K),respectively.