高Cu铝硅压铸合金及其热处理研究

发布时间：2018-06-08 06:32

  本文选题：高Cu压铸铝合金 + 拉伸性能　； 参考：《重庆大学》2015年硕士论文

【摘要】：轻量化推动着以铝合金为代表的轻合金获得越来越广泛的应用。压铸作为最广泛应用的液态成形方法,常用于铝合金大型复杂薄壁铸件的生产。但常用压铸铝硅合金的性能较低。因此,开发适合压铸的高强韧铝合金,是进一步为铝压铸件减重的有效途径。铜是铝的常用固溶合金化元素。本文以A356铸造合金为对象,通过实验性压铸、金相观察、拉伸性能检测、断口扫描电子显微表征等方法,研究较高Cu添加量(4%-6%)时,Cu对A356的铸态、T6热处理态的组织、拉伸性能及断裂行为的影响,并得到如下结论:①Cu含量超过5%时,会导致A356的充型性能略有下降,但在压铸成型下,这种下降对铸件的成型能力的影响并不明显。②A356压铸组织中主要是条片状的Si相。添加Cu后,合金中出现Al2Cu相,该相分布在Si相四周及晶界上。随着Cu含量的升高,Si相由条片状变为团聚的骨骼状。可能是因为Si四周的Al2Cu相增多,原有的条片状的Si相被打断,形成团聚的细小的Si相。除了主要的强化相Al2Cu相以外,组织中还生成了强化相W(AlxMg5Si4Cu4)。③压铸A356抗拉强度为206MPa,延伸率达到8.89%。添加Cu后,合金强度得到较明显提升,当Cu含量为5.5%时,合金的抗拉强度达到299MPa的最大值,此时延伸率为6.52%;但Cu过高会明显降低合金的塑性,Cu含量达到6%时,抗拉强度下降到270MPa,延伸率仅有3.77%。④530℃×3h固溶热处理后,合金在160℃下的时效硬化在3h时达到硬度峰值(74.5HRE);在随后的时效过程中,合金硬度一直在低于峰值的小范围内波动。压铸态条片状Si相在2h左右的固溶处理后基本完成球化,随着固溶时间的延长而分布更加均匀;时效过程中,合金组织变化不明显。固溶处理后,压铸试样表面出现大小、分布不均匀的气泡。⑤T6热处理后,不同含Cu量试样的拉伸性能都有一定的提升,且全部试样的延伸率超过了5%。其中,Cu含量为4.5%的合金的综合机械性能最佳,具有337MPa的抗拉强度、6.23%延伸率。⑥铸态拉伸断口为宏观脆性断裂、微观准解理断裂。断口没有肉眼可观察到的气孔,但显微镜下可观察到缩松缺陷。T6热处理后,合金宏观断裂模式仍为脆性断裂,但微观是准解理和韧性混合断裂模式;断口上出现可肉眼观察到的小气孔,显微镜下可观察到尺寸扩大的缩松缺陷。
[Abstract]:Light weight has promoted the application of aluminum alloy as the representative of light alloy more and more widely. As the most widely used liquid forming method, die casting is often used in the production of large complex thin-walled aluminum alloy castings. However, the properties of commonly used die-cast Al-Si alloys are relatively low. Therefore, the development of high strength and toughness aluminum alloy suitable for die casting is an effective way to further reduce the weight of aluminum die casting. Copper is a common solution alloying element of aluminum. In this paper, by means of experimental die-casting, metallographic observation, tensile property test and fracture scanning electron microscopy (SEM), the microstructure of the as-cast T6 heat treated A356 alloy with higher Cu content (4% -6%) was studied by means of experimental die-casting, metallographic observation, tensile property test, and scanning electron microscopy (SEM). The effect of tensile properties and fracture behavior on the properties of A356 was obtained. It is concluded that the filling properties of A356 decrease slightly when the ratio of 1: 1 Cu is higher than 5, but under the condition of die casting, The effect of this decline on the molding ability of casting is not obvious. 2A356 die casting structure is mainly a slice of Si phase. After the addition of Cu, the Al _ 2Cu phase appears in the alloy, which distributes around the Si phase and on the grain boundary. With the increase of Cu content, the Si phase changed from strip to bone. This may be due to the increase of Al _ 2Cu phase around Si and the interruption of the original lamellar Si phase to form a fine and agglomerated Si phase. In addition to the main strengthening phase Al _ 2Cu, the strengthening phase Wy Al _ Xmg _ 5Si _ 4Cu _ 4C _ 3 die-cast A356 has a tensile strength of 206 MPA and an elongation of 8.89 MPA. When Cu was added, the tensile strength of the alloy increased obviously. When Cu content was 5.5, the tensile strength of the alloy reached the maximum value of 299MPa, and the elongation of the alloy reached 6.52.However, when Cu was too high, the plastic Cu content of the alloy reached 6g. The tensile strength decreases to 270MPa, and the elongation is only 3.770.4530 鈩，

本文编号：1994948