Mg元素含量对Al-2Si-0.8Fe合金抗退火软化和导电性能的影响

Effect of Mg element content on annealing softening resistance and electrical conductivity of Al-2Si-0.8Fe alloy

采用光学显微镜、扫描电镜、布氏硬度计、电子万能材料试验机和涡流导电仪等研究了Mg元素含量对Al-2Si-0.8Fe合金的微观组织、力学性能及导电性能的影响。结果表明:随着Mg元素含量的增加,铸态Al-2Si-0.8Fe合金的硬度和抗拉强度不断提高,而对其导电性能的影响相对较小;当Mg含量增至1.5%时,铸态合金的硬度和抗拉强度达到最大值,分别为77.1 HBW和190 MPa,较Al-2Si-0.8Fe合金的硬度(42.3 HBW)和抗拉强度(123.5 MPa)分别提升了82.3%和53.8%,而导电性能的下降幅度控制在2.9%以内。低温退火处理后,合金的导电率有所提升;当Mg含量超过1%时,退火态合金的硬度显著降低,出现退火软化现象;而在Mg含量低于1%时,退火态合金的抗拉强度和硬度并未明显下降,分别达到201.7 MPa和78 HBW,显示出良好的抗退火软化特性。添加少量的Mg后,合金的组织主要由初生α-Al、共晶Mg_(2)Si相以及长针状β-Al_(5)FeSi相构成,而随着Mg含量的增加,会发生β-Al_(5)FeSi→π-Al_8Mg_(3)FeSi_(6)反应,导致合金中Mg_(2)Si强化相数量减少,无法弥补铸态合金固溶强化对硬度的提升效果,从而产生退火软化现象。

Effect of Mg element content on microstructure,mechanical properties and electrical conductivity of Al-2Si-0.8Fe alloy was studied by means of optical microscope,scanning electron microscopy,Brinell hardness tester,electronic universal material testing machine and eddy current conductivity tester.The results show that with the increase of Mg element content,the hardness and tensile strength of the as-cast Al-2Si-0.8Fe alloy continuously increase,while the influence on its electrical conductivity is relatively small.When the Mg content increases to 1.5%,the hardness and tensile strength of the as-cast alloy reach their maximum values,which are 77.1 HBW and 190 MPa,respectively.Compared with the hardness(42.3 HBW)and tensile strength(123.5 MPa)of the Al-2Si-0.8Fe alloy,they increase by 82.3%and 53.8%,respectively,while the decrease in electrical conductivity is limited to within 2.9%.After low-temperature annealing treatment,the electrical conductivity of the alloy is improved.When the Mg content exceeds 1%,the hardness of the annealed alloy significantly decreases and annealing softening occurs.When the Mg content is below 1%,the tensile strength and hardness of the annealed alloy do not significantly decrease,reaching 201.7 MPa and 78 HBW,respectively,showing good resistance to annealing softening.After adding a small amount of Mg,the microstructure of the alloy is mainly composed of primaryα-Al,eutectic Mg_(2) Si phase and long acicularβ-Al 5FeSi phase.With the increase of Mg content,a reaction of β-Al_(5)FeSi→π-Al_8Mg_(3)FeSi_(6)occurs,resulting in a decrease in the number of Mg_(2) Si strengthening phases in the alloy,which cannot compensate for the hardening effect of solid solution strengthening on the hardness of the as-cast alloy,leading to annealing softening phenomenon.