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采用金相显微镜和电子拉伸机,研究了6061合金半固态坯料的电磁半连续铸造、二次加热、触变模锻成形以及成形件热处理。结果表明:采用近液相线电磁半连续铸造技术制备的6061合金半固态坯料微观组织为均匀、细小非枝晶组织;低过热度浇铸时,临界晶核半径减小,此时在电磁场作用下,降低了熔体的温度梯度,促进了准固相原子团簇在熔体中形成,形核率增大;二次加热时,初生α-Al不断球化,淬火组织也呈圆整状,620±5℃、保温15 min,模具温度250~300℃,留模时间10~15 s,触变成形出表面光洁的成形件;经T5处理后,抗拉强度达到328 MPa,延伸率达到8%,大大高于压铸成形件的性能。半固态压铸成形由于成形速度高,溶体高速充型,造成成形件气孔率高,使成形件组织致密度不如半固态模锻成形件,这是半固态压铸件强度低、模锻件强度高的主要原因。
The semi-continuous casting of semi-solid 6061 alloy, secondary heating, thixoforming and heat treatment of forming parts were studied by metallographic microscope and electronic stretching machine. The results show that the microstructure of 6061 alloy semi-solid billets prepared by near-liquidus electromagnetic semi-continuous casting technology is uniform and fine non-dendritic microstructure. The critical crystal nucleus radius decreases when casting with low superheat degree. Under the action of electromagnetic field , Reducing the temperature gradient of the melt, promoting the formation of quasi-solid atomic clusters in the melt and increasing the nucleation rate. During the secondary heating, the primary α-Al continuously spheroidizes and the quenched structure is also rounded. 620 ± 5 ℃, holding for 15 min, mold temperature of 250 ~ 300 ℃ and mold holding time of 10 ~ 15 s, thixoformed to form smooth surface forming parts. After T5 treatment, the tensile strength reached 328 MPa and elongation reached 8 %, Much higher than the performance of die-casting parts. Semi-solid die-casting forming due to high forming speed, high-speed melt filling, resulting in high porosity of the forming part, the forming part of the fabric density as semi-solid forging, which is the semi-solid die-casting low strength die forging the main high strength the reason.