Si含量对高强高韧7050铝合金组织和力学性能的影响

通过熔炼制备8种不同杂质Si含量的7050铝合金，研究了Si含量从0.033%~0.491%的变化对7050铝合金组织和力学性能的影响规律.结果表明：当Si含量增加至0.134%时，合金铸态组织中出现明显的粗大富Si杂质相，并且随Si含量增加，富Si杂质相含量增多；粗大富Si杂质相在均匀化退火、热挤压以及固溶处理过程中都难以溶解，残留在时效态合金组织中；当Si含量增加至0.134%时，时效态合金的室温拉伸强度和塑性明显提高；在Si含量高于0.344%后，Si含量的增加使合金的室温拉伸强度、塑性和断裂韧性都显著降低.为获得最佳的室温强度和塑性，7050铝合金的Si含量应控制在0.121%~0.134%，但要获得更好的断裂韧性，需进一步降低合金中Si含量.

Influence of Si Contents on Microstructures and Mechanical Properties of High Strength and Toughness 7050 Aluminum Alloys

Eight kinds of 7050 aluminum alloys with different Si contents have been prepared by cast. The influence of Si contents from 0.033% to 0.491% on microstructures and mechanical properties has been investigated. The results show that significant coarse Si-rich impurity phase has been found in as-cast microstructures when Si content is increased to 0.134%, and the content of this phase is increased with Si content increasing. The coarse Si rich impurity phases are insoluble during homogenizing annealing, hot extrusion and solution treatment, and remain in aged microstructures of alloys. The aged alloy with 0.134%Si has the highest tensile strength and plasticity at room temperature. The strength, plasticity and fracture toughness reduce significantly when Si content is higher than 0.344%. Si content should be controlled in the range of 0.121% to 0.134% to get the best strength and plasticity. To obtain a better fracture toughness, the Si content in the alloy should be further reduced.