压铸Al-10Si-0.3Mg合金的组织和力学性能研究
发布时间：2018-11-22 09:32
【摘要】：近年来,随着我国汽车工业的飞速发展,铝合金作为目前交通工具轻量化中替代钢铁的首选材料,逐渐在汽车行业中得到越来越广泛地运用。在汽车用铝合金中,真空压铸铝合金以其良好的表面质量、优异的力学性能以及较高的材料利用率等优点,在汽车用铝合金零部件中占有极其重要的地位。以Aural-2(Al-10Si-0.3Mg)为代表的高塑性压铸铝合金的开发推动了铝合金大铸件在汽车结构件上的应用。本文以厚度为2.5mm和5.0mm的真空压铸Aural-2(Al-10Si-0.3Mg)铝合金薄板作为研究对象。在汽车工业上,真空压铸Al-10Si-0.3Mg合金通常用于制造形状复杂的大型薄壁汽车部件。汽车的复杂结构将使不同部位对合金构件的厚度要求存在差异,使得合金在制作成压铸部件后存在尺寸不均的问题,因此本文首先将对不同壁厚合金的铸态组织进行对比分析,研究冷却速率对合金凝固组织和性能的影响。此外,为了改善合金的综合力学性能,特别是塑性方面,本文随后将对合金进行固溶和时效处理,采用光学显微镜(OM)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等分析手段,并通过室温力学性能拉伸试验,系统研究热处理工艺对合金的微观组织和力学性能的影响,获得合金的最佳热处理工艺参数。同时通过观察热处理后合金的拉伸断口形貌和拉伸断口纵向面的微观组织,对影响合金拉伸断裂的因素和合金的断裂行为进行分析探讨。研究结果表明:(1)两种壁厚合金的铸态组织沿厚度方向均呈不均匀分布:2.5mm厚合金的铸态组织沿厚度方向呈梯度分布,可以观察到不太明显的 三明治‖结构,而5mm厚合金的铸态组织沿厚度方向呈明显的 三明治‖结构分布,即表层区+心部区+表层区。随着冷却速率的增加,合金的微观组织得到细化。相较于5.0mm厚合金,2.5mm厚合金表层细晶区比例由35%增加到40%左右,同时合金中共晶硅的纤维化趋势增加。铸态下,2.5mm厚合金的硬度、抗拉强度、屈服强度及伸长率依次为106.9HV、303.1MPa、164.2MPa、7.6%。;当冷却速率较低,合金厚度为5.0mm时,其硬度、抗拉强度、屈服强度及伸长率分别下降到91HV、227.4MPa、115.3MPa、5.8%。(2)固溶处理将提高合金基体内固溶的Mg元素和Si元素含量。同时在此过程中,合金中的共晶硅形貌将向粒状化和球状化转变。在时效处理过程中,2.5mm厚合金将有沉淀硬化相析出,主要是占主导的细针状β‖相、少量杆状β’相和颗粒Si相。其中,β‖析出相的横断面直径约10-18nm,长度约200-800nm;β’析出相的横断面直径约20-38nm,长度为600-1400nm,两者均沿着基体的001方向分布。(3)人工时效可以显著改善合金的力学性能。在本文设定的热处理工艺条件下,2.5mm厚合金在最佳热处理工艺参数450℃/1.5h+225℃/1h下,其抗拉强度、屈服强度及伸长率依次为212.2MPa、113.1MPa、16%;5.0mm厚合金在最佳热处理工艺参数450℃/1.5h+225℃/2h下,其抗拉强度、屈服强度及伸长率依次为184.5MPa、118.7MPa、8.73%。(4)通过对合金的拉伸断口形貌和拉伸断口纵向面微观组织的分析可知,热处理后合金的断裂类型为韧性断裂,同时合金中共晶硅颗粒的尺寸和取向将对合金的拉伸性能产生影响。合金在拉伸过程中,将发生第二相的开裂、微裂纹的萌生与生长和微裂纹的连接三个过程,最终合金的断裂方式将是沿晶断裂和穿晶断裂两种方式的结合。
[Abstract]:In recent years, with the rapid development of the automobile industry in China, the aluminum alloy has been widely used in the automobile industry as the preferred material for replacing iron and steel in the light weight of the current vehicle. In the aluminum alloy for automobiles, the vacuum die-casting aluminum alloy has the advantages of good surface quality, excellent mechanical property and high material utilization ratio, and plays an extremely important role in automobile aluminum alloy parts. The development of high-plastic die-cast aluminum alloy represented by Auural-2 (Al-10Si-0. 3Mg) has promoted the application of the aluminum alloy large-cast to the structural parts of the automobile. The Al-10Si-0.3Mg (Al-10Si-0. 3Mg) aluminum alloy sheet with a thickness of 2. 5 mm and 5. 0mm is used as the research object. In the automotive industry, the vacuum die-cast Al-10Si-0. 3Mg alloy is commonly used to make large thin-walled automobile parts with complex shapes. The complicated structure of the automobile will make the difference of the thickness of the alloy component in different parts, so that the alloy has the problem of non-uniform size after making the die-casting part, The effect of cooling rate on the microstructure and properties of the alloy was studied. In addition, in order to improve the comprehensive mechanical properties of the alloy, in particular the plastic aspect, the alloy is subjected to solid solution and aging treatment, and an optical microscope (OM), a scanning electron microscope (SEM) and a transmission electron microscope (TEM) are used to analyze the alloy. The effect of heat treatment on the microstructure and mechanical properties of the alloy was studied by mechanical tensile test at room temperature, and the optimum heat treatment process parameters of the alloy were obtained. At the same time, by observing the tensile fracture morphology of the alloy after heat treatment and the microstructure of the longitudinal surface of the tensile fracture, the factors affecting the tensile fracture of the alloy and the fracture behavior of the alloy are analyzed. 鐮旂┒缁撴灉琛ㄦ槑:(1)涓ょ澹佸帤鍚堥噾鐨勯摳鎬佺粍缁囨部鍘氬害鏂瑰悜鍧囧憟涓嶅潎鍖，
本文编号：2348877
[Abstract]:In recent years, with the rapid development of the automobile industry in China, the aluminum alloy has been widely used in the automobile industry as the preferred material for replacing iron and steel in the light weight of the current vehicle. In the aluminum alloy for automobiles, the vacuum die-casting aluminum alloy has the advantages of good surface quality, excellent mechanical property and high material utilization ratio, and plays an extremely important role in automobile aluminum alloy parts. The development of high-plastic die-cast aluminum alloy represented by Auural-2 (Al-10Si-0. 3Mg) has promoted the application of the aluminum alloy large-cast to the structural parts of the automobile. The Al-10Si-0.3Mg (Al-10Si-0. 3Mg) aluminum alloy sheet with a thickness of 2. 5 mm and 5. 0mm is used as the research object. In the automotive industry, the vacuum die-cast Al-10Si-0. 3Mg alloy is commonly used to make large thin-walled automobile parts with complex shapes. The complicated structure of the automobile will make the difference of the thickness of the alloy component in different parts, so that the alloy has the problem of non-uniform size after making the die-casting part, The effect of cooling rate on the microstructure and properties of the alloy was studied. In addition, in order to improve the comprehensive mechanical properties of the alloy, in particular the plastic aspect, the alloy is subjected to solid solution and aging treatment, and an optical microscope (OM), a scanning electron microscope (SEM) and a transmission electron microscope (TEM) are used to analyze the alloy. The effect of heat treatment on the microstructure and mechanical properties of the alloy was studied by mechanical tensile test at room temperature, and the optimum heat treatment process parameters of the alloy were obtained. At the same time, by observing the tensile fracture morphology of the alloy after heat treatment and the microstructure of the longitudinal surface of the tensile fracture, the factors affecting the tensile fracture of the alloy and the fracture behavior of the alloy are analyzed. 鐮旂┒缁撴灉琛ㄦ槑:(1)涓ょ澹佸帤鍚堥噾鐨勯摳鎬佺粍缁囨部鍘氬害鏂瑰悜鍧囧憟涓嶅潎鍖，
本文编号：2348877
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