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研究了浇注温度和固溶温度对挤压铸造Al-6.8Zn-2.5Mg-2.0Cu合金组织和性能的影响。结果表明,与金属型重力铸造相比,挤压铸造可以显著细化合金的微观组织,减少铸件缩松缺陷,从而提高其力学性能。在金属型重力铸造下,初生α-Al相晶粒尺寸随着浇注温度的增加而增大。在挤压力为60MPa时,随浇注温度的增加,α-Al相晶粒尺寸先减小而后增加。在浇注温度为720℃时,凝固组织的二次枝晶间距最小,约为26.3μm,铸件的抗拉强度和伸长率分别为310 MPa和4.0%。铸件经过470℃固溶10h+130℃时效24h热处理后,抗拉强度和伸长率分别达到590MPa和4.7%,获得了良好的强韧化效果。
The effects of pouring temperature and solution temperature on microstructure and properties of squeeze cast Al-6.8Zn-2.5Mg-2.0Cu alloy were investigated. The results show that, compared with metal gravity casting, squeeze casting can remarkably refine the microstructure of the alloy and reduce the shrinkage defects of castings so as to improve the mechanical properties. Under metal gravity casting, the grain size of primary α-Al phase increases with the increase of pouring temperature. When the extrusion pressure is 60 MPa, the grain size of α-Al phase first decreases and then increases with the increase of pouring temperature. When the pouring temperature is 720 ℃, the secondary dendritic spacing of the solidified structure is the smallest, about 26.3μm. The tensile strength and elongation of the castings are 310 MPa and 4.0% respectively. After heat treatment at 470 ℃ for 10h + 130 ℃ for 24h, the tensile strength and elongation of the castings reached 590MPa and 4.7%, respectively. Good toughness was obtained.