含B高导电Al-Si合金显微组织的观察与分析

Observation and Analysis of Microstructure of the B-Containing Highly Conductive Al-Si Alloy

通过电导率测量、金相观察、扫描电镜分析、透射电镜分析、X射线衍射分析和电子探针微量分析,研究了B的添加对铸造Al-Si合金晶格常数、晶粒尺寸和导电性能的影响。研究结果表明:当B的质量分数低于0.02%时,Al基体内各杂质元素Ti、Cr、Mn、V均以硼化物的形式从Al基体内析出,Al基体内的晶格畸变程度明显降低,电导率提高了6.45%;当B的质量分数超过0.02%时,B与Ti作用形成TiB_2,TiB_2促进Al3Ti相的形成,TiB_2和Al_3Ti共同促进晶粒细化,晶界增多,电子散射几率增加,同时过量的B固溶在Al基体内,电导率下降了2.55%;当B的质量分数为0.02%时,在保证合金的抗拉强度不降低的同时,合金的电导率达到最好,为33.00%IACS。

The effects of B addition on the lattice constant, grain size and electrical property of Al-Si cast alloys were investigated by Wheatstone bridge conductivity measurement, optical microscope, scanning electron microscope（SEM）, transmission electron microscope（TEM）,X-ray diffraction（XRD） and electron probe micro-analyzer（EPMA） analysis. Results indicate that impurities of Ti, Cr, Mn, V are converted from solid solution state to boride in the Al matrix when B content is below 0.02%; meanwhile, the degree of lattice distortion decreases which results in the increase of the conductivity by 6.45%. When the B content is over 0.02%, TiB2 from the reaction of B and Ti, promotes the formation of Al3 Ti phase with the increase of B content; TiB2 and Al3 Ti lead to finer grains and more crystal distortion, enhance the risk of electron scattering and the excess B dissolves in the Al matrix simultaneously; as a result, the conductivity decreases by 2.55%. When the B content is 0.02%, the electrical property of the alloy is the best and the conductivity is 33.00%IACS, based on the premise that the tensile strength is not reduced.