6061铝合金自孕育流变压铸薄壁件制备及组织性能

Microstructure and mechanical properties of 6061 aluminum alloy thin-walled diecasting prepared by self-inoculation method

采用自孕育法制备6061变形铝合金半固态浆料,研究浆料保温时间对自孕育流变压铸件凝固组织及力学性能的影响,并分析了压铸件不同部位的凝固组织及其差异形成的原因。结果表明:自孕育法可有效改善6061铝合金传统铸造形成的粗大树枝晶组织,制备出具有等轴状或球状初生α-Al晶粒的铸件。采用自孕育法制浆结合高压压铸能成形完整的6061铝合金半固态流变压铸件。相比传统金属型铸造和液态高压压铸,自孕育流变压铸能显著提高铸件的力学性能。浆料等温保温过程中,初生α-Al晶粒尺寸随着保温时间的延长逐渐增大且逐渐圆整,在保温时间为5 min时获得的流变压铸件组织最为圆整,力学性能最好,过长的保温时间会恶化组织并显著降低铸件的力学性能。对于同一参数的压铸件,随着浆料充型距离的增加,模具冷却速率逐渐增大,压铸件内部组织差异明显。

The semi-solid slurry of 6061 wrought aluminum alloy was prepared by self-inoculation method(SIM),the effect of isothermal holding time on microstructure and mechanical properties of rheo-diecastings was investigated,and the solidification structure of different parts of the rheo-diecastings and the reasons for their differences were analyzed.The results indicate that the coarse dendrite structure of the 6061 aluminum alloy formed by traditional casting can be effectively modified by self-inoculation method(SIM),and the castings with equiaxed or spherical primary α-Al grains can be prepared by SIM.The completed rheo-diecastings of the 6061 aluminum alloy can be prepared by SIM combined with high pressure die casting.Compared with traditional metal casting and liquid high pressure die casting,the mechanical properties of the SIM rheo-diecastings are significantly improved.During the isothermal holding process of the slurry,the average size of primary α-Al grains increases gradually and gradually round with the increase of the holding time.The microstructure of the rheo-diecastings is the roundest and its mechanical properties are the highest when the holding time is 5 min,and too long holding time will deteriorate the microstructure and significantly reduce the mechanical properties of the rheo-diecastings.For die castings with the same parameters,the die cooling rate gradually increases with the increase of slurry filling distance,and the internal microstructure difference of the rheo-diecastings is obvious.