本文選題：高Cu壓鑄鋁合金 + 拉伸性能　； 參考：《重慶大學(xué)》2015年碩士論文

【摘要】：輕量化推動著以鋁合金為代表的輕合金獲得越來越廣泛的應(yīng)用。壓鑄作為最廣泛應(yīng)用的液態(tài)成形方法,常用于鋁合金大型復(fù)雜薄壁鑄件的生產(chǎn)。但常用壓鑄鋁硅合金的性能較低。因此,開發(fā)適合壓鑄的高強韌鋁合金,是進一步為鋁壓鑄件減重的有效途徑。銅是鋁的常用固溶合金化元素。本文以A356鑄造合金為對象,通過實驗性壓鑄、金相觀察、拉伸性能檢測、斷口掃描電子顯微表征等方法,研究較高Cu添加量(4%-6%)時,Cu對A356的鑄態(tài)、T6熱處理態(tài)的組織、拉伸性能及斷裂行為的影響,并得到如下結(jié)論:①Cu含量超過5%時,會導(dǎo)致A356的充型性能略有下降,但在壓鑄成型下,這種下降對鑄件的成型能力的影響并不明顯。②A356壓鑄組織中主要是條片狀的Si相。添加Cu后,合金中出現(xiàn)Al2Cu相,該相分布在Si相四周及晶界上。隨著Cu含量的升高,Si相由條片狀變?yōu)閳F聚的骨骼狀�？赡苁且驗镾i四周的Al2Cu相增多,原有的條片狀的Si相被打斷,形成團聚的細小的Si相。除了主要的強化相Al2Cu相以外,組織中還生成了強化相W(AlxMg5Si4Cu4)。③壓鑄A356抗拉強度為206MPa,延伸率達到8.89%。添加Cu后,合金強度得到較明顯提升,當Cu含量為5.5%時,合金的抗拉強度達到299MPa的最大值,此時延伸率為6.52%;但Cu過高會明顯降低合金的塑性,Cu含量達到6%時,抗拉強度下降到270MPa,延伸率僅有3.77%。④530℃×3h固溶熱處理后,合金在160℃下的時效硬化在3h時達到硬度峰值(74.5HRE);在隨后的時效過程中,合金硬度一直在低于峰值的小范圍內(nèi)波動。壓鑄態(tài)條片狀Si相在2h左右的固溶處理后基本完成球化,隨著固溶時間的延長而分布更加均勻;時效過程中,合金組織變化不明顯。固溶處理后,壓鑄試樣表面出現(xiàn)大小、分布不均勻的氣泡。⑤T6熱處理后,不同含Cu量試樣的拉伸性能都有一定的提升,且全部試樣的延伸率超過了5%。其中,Cu含量為4.5%的合金的綜合機械性能最佳,具有337MPa的抗拉強度、6.23%延伸率。⑥鑄態(tài)拉伸斷口為宏觀脆性斷裂、微觀準解理斷裂。斷口沒有肉眼可觀察到的氣孔,但顯微鏡下可觀察到縮松缺陷。T6熱處理后,合金宏觀斷裂模式仍為脆性斷裂,但微觀是準解理和韌性混合斷裂模式;斷口上出現(xiàn)可肉眼觀察到的小氣孔,顯微鏡下可觀察到尺寸擴大的縮松缺陷。
[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，

本文編號：1994948