低频电磁半连续铸造对4045合金显微组织与性能的影响

Effect of Low Frequency Electromagnetic Casting on Microstructure and Properties of 4045 Alloy

采用普通DC铸造和低频电磁半连续铸造工艺,制备了Φ100 mm的4045铝合金锭坯,并利用光学电子显微镜和扫描电镜对铸锭的显微组织进行检测与分析,用显微硬度计和电子拉伸试验机对铸锭的力学性能进行检测。结果表明,采用低频电磁半连续铸造,铸锭的显微组织中的-αAl枝晶组织被明显打碎,成为细小均匀的枝晶组织;共晶Si也较普通DC铸造组织中的共晶Si细小、均匀。在铸锭外表层附近存在富Si区域,但采用低频电磁半连续铸造,富Si区域明显减小。采用低频电磁半连续铸造,初生-αAl中的硅含量增加,达到2.79%,合金的力学性能也得到提高,bσ为225 MPa、ψ为11.4%、硬度为HV 69.5。

Under low frequency electromagnetic field, 4045 alloys were semi-continuously cast into ingots with 100 mm in diameter. Microstructures of samples taken from different part of the cast with different cooling conditions were characterized by optical microscopy and scanning electron microscopy （SEM）. Unlike casting without electromagnetic field, the α-Al dendrites were found to be thin and homogeneous under low frequency electromagnetic field. The eutectic Si grains are homogeneous with fine dimensions. Also, the Si-rich region formed at the edge of the ingot was found to be significantly decreased under low frequency electromagnetic field. The content of silicon in the primary aluminum reached to 2.59 %（wt）. The mechanical properties of the electromagnetic modifying casting 4045 aluminum alloy improved with σb （ultimate tensile strength）of 225 MPa, ψ（elongation percentage）of 11.36% and HV（Vickers diamond hardness） of 69.5 MPa.