超低速压铸ADC12合金的铸态和热处理态组织和性能研究

Microstructure and Mechanical Properties of ADC12 Alloy by Super Slow Speed Die Casting at As-cast and Heat-treated State

采用超低速（0.05-0.9 m/s）压铸制备了ADC12合金样件,并对其进行了固溶时效热处理,研究了不同状态下合金的组织和力学性能。结果表明,在铸态下,超低速压铸ADC12合金具有高的力学性能,因为合金组织中共晶硅颗粒细小、圆整;该铸态合金能够进行热处理强化,经过固溶和时效热处理,合金强度和塑性较铸态有显著提高,因为合金组织中共晶硅颗粒更加球化,而且分布更均匀,金属间化合物从骨骼状逐渐粒化;170℃时效10 h后,其拉伸强度、屈服强度和伸长率较日本标准分别提高78.3%、104.0%和257.1%;而且在170-190℃,时效4-10 h,时效参数对强度的影响不显著;无论铸态还是热处理态,金属间化合物都是该材料断裂时的裂纹源。

ADC12 alloy castings were produced by super slow speed （SSS） die casting, its microstructure and mechanical properties at as-cast and heat-treated were researched. The results show that, at as-cast, the SSS casting has high mechanical properties due to fine eutectic silicon particles. The SSS casting can be heat-treated. The mechanical properties of SSS castings after solid dissolving and aging are greatly improved comparing with those as-cast, because the eutectic silicon particle is more spherized and evenly distributed in a phase, and intermetallic compounds contained A1, Si, Fe, Cu, Mn are granulated from rib shape. For example, the tensile strength, 0.2% yield strength and the ductility of the alloy after 520 ℃ solid dissolving and 170 ℃ aging treatment are increased by 41.2%, 104.0% and 257.1%,respectively, compared with the values in JIS H5302-2000. And the parameters varying in 170-190 ℃ for 4-10 h don＇t influence the strength obviously. However, the intermetallic compounds with different shape and size are found to be the origins of cracks in tensile condition.