Microstructure and properties of spray-formed high-strength Al-Zn-Mg-Cu alloy containing manganese
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摘要: 利用噴射成形和熱擠壓的方法制備了含錳為2%(質量分數)的高強鋁合金Al-8.8Zn-2.9Mg-1.6Cu合金,用X射線衍射(XRD)、光學顯微鏡(OM)和掃描電鏡(SEM)和透射電鏡(TEM)等方法研究了鋁合金的微觀組織,并進行了力學性能測試.研究結果表明:噴射成形制備的含錳鋁合金經過熱擠壓和固溶處理后,基體組織為細小均勻的再結晶晶粒組織,平均尺寸約8μm.MnAl6顆粒在噴射沉積過程中沿晶界析出,經過熱擠壓后,尺寸大的顆粒破碎,大部分的顆粒則沿擠壓方向產生一定的塑性變形.固溶處理對MnAl6顆粒尺寸的影響不明顯,但棒狀/片狀顆粒的邊角處發生球化,有利于降低誘發顯微裂紋的應力或應變集中.時效后,鋁合金達強度為775MPa,延伸率達4.3%,斷口以細小的韌窩為主,尺寸小于500nm.Abstract: An Al-Zn-Mg-Cu alloy containing 2% Mn (mass fraction) was prepared by spray forming method and hot extrusion. The microstructure and mechanical properties of the spray-deposited Al alloy were studied by optical microscopy, scanning electron microscopy, X-ray diffraction, and tensile tests. The results show that the Al alloy has uniformly fine recrystallized grains with an average size of 8μm after hot extrusion and solid solution treatment. MnAl6 particles were precipitated at grain boundaries during the spray forming process, most of the MnAl6 particles were plastically deformed to some extent along the direction of extrusion during the hot extrusion process, and some large MnAl6 particles were fragged. The effect of solution treatment on the size of MnAl6 particles is negligible but the spheroidization of rod-like/plate-like particles occurred at the corner of these particles. The spheroidization of MnAl6 particles is benefit to the decrease of stress or strain concentration which would induce microcracks. When aged at 120℃ for 24 h, the tensile strength of the Al alloy was increased up to 775 MPa with an elongation of 4.3%, and the fracture surface consisted mainly of dimples with a size lower than 500 nm.
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Key words:
- ultra-high strength aluminum alloy /
- manganese /
- microstructure /
- mechanical properties /
- spray forming /
- hot extrusion
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