【摘要】：鋁合金被用于船舶制造已有上百年的歷史。隨著造船業(yè)的發(fā)展,船舶輕量化越來越受重視,艦船材料對于鋁合金材料的屈服強度和耐蝕性的要求越來越高。A357合金鑄造性能優(yōu)異,抗疲勞、抗腐蝕性能、氣密性好,在航空航天、汽車工業(yè)已廣泛使用。通過優(yōu)化A357合金的成分和工藝,在不降低其耐蝕性的前提下提高屈服強度,具有非常重要的實用價值。本文研究了Si、Cu、Mg、Mn合金元素對金屬型鑄造鋁硅合金屈服強度和耐蝕性能的影響。設(shè)計四因素三水平正交實驗,綜合各因素對合金屈服強度、延伸率和耐蝕性的影響,確定最優(yōu)成分;分析了不同Sr濃度對優(yōu)化成分合金的變質(zhì)效果;通過金相顯微鏡、SEM觀察合金的微觀組織;研究了最優(yōu)成分合金的最佳時效工藝;觀察合金的斷口形貌并分析斷裂機理;分析對比了最優(yōu)成分合金和A357合金的耐腐蝕性。研究表明隨著Si、Mg、Cu元素濃度的升高,合金的屈服強度增大;隨著Si元素濃度的升高,合金的延伸率減小,耐蝕性先略微減弱后增強;隨著Cu元素濃度的升高,耐蝕性顯著減弱;優(yōu)化后的成分為Si:8.3 wt.%,Cu:0.1 wt.%,Mg:1.0 wt.%,Mn:0.1 wt.%。0.06 wt.%Sr對最優(yōu)成分合金中的硅具有良好的變質(zhì)和細(xì)化效果;熱處理后硅相呈顆粒狀分布在基體中,粒度在5μm左右;富錳相呈細(xì)小顆粒狀分布;Cu、Mg元素主要以彌散的脫溶相的形式分布在基體中;過變質(zhì)的鋁合金晶界元素富集嚴(yán)重,延伸率很低。最優(yōu)成分的合金的最佳時效工藝為時效溫度170℃時,時效時間為8h;此工藝下合金的屈服強度為322.5MPa,延伸率3.2%,耐蝕性優(yōu)于A357鋁合金。不同成分的合金斷口形貌均為穿晶韌性斷口;硅含量不同對斷口形貌影響顯著,隨著硅含量的升高,韌窩面積逐漸變小,深度逐漸變淺;基體中脆性相逐漸增多,撕裂棱也逐漸增多,合金塑性變差。
[Abstract]:Aluminum alloys have been used in shipbuilding for hundreds of years. With the development of shipbuilding industry, more and more attention has been paid to the lightening of ships, and the requirements of ship materials for the yield strength and corrosion resistance of aluminum alloy are higher and higher. A357 alloy has excellent casting performance, fatigue resistance, corrosion resistance and air tightness. In aerospace, the automobile industry has been widely used. By optimizing the composition and process of A357 alloy, it is of great practical value to improve the yield strength without reducing the corrosion resistance of A357 alloy. In this paper, the effect of Si,Cu,Mg,Mn alloy elements on the yield strength and corrosion resistance of Al-Si alloy in metal mold casting has been studied. The orthogonal experiment of four factors and three levels was designed to determine the optimum composition by synthesizing the effects of each factor on the yield strength, elongation and corrosion resistance of the alloy, and the modification effect of different Sr concentration on the alloy with optimized composition was analyzed. The microstructure of the alloy was observed by SEM; the optimum aging process of the alloy was studied; the fracture morphology of the alloy was observed and the fracture mechanism was analyzed; and the corrosion resistance of the optimum composition alloy and A357 alloy was analyzed and compared. The results show that the yield strength of the alloy increases with the increase of the concentration of Si,Mg,Cu element, the elongation of the alloy decreases with the increase of the concentration of Si element, and the corrosion resistance of the alloy decreases slightly and then increases with the increase of the concentration of Si element. The corrosion resistance decreased with the increase of Cu concentration. The optimized composition is Si:8.3 wt.%,Cu:0.1 wt.%,Mg:1.0 wt.%,Mn:0.1 wt.%.0.06 wt.%Sr, which has good modification and refinement effect on silicon in the optimal composition alloy. After heat treatment, the silicon phase is granular in the matrix, the particle size is about 5 渭 m, the manganese rich phase is a fine granular distribution, and the Cu,Mg element is mainly distributed in the matrix in the form of dispersive desolvent phase. The overmodified aluminum alloy is rich in grain boundary elements and its elongation is very low. The best aging process of the alloy with the optimum composition is that the aging temperature is 170 鈩，

本文編號：2417568