發(fā)布時間：2018-11-02 15:38

【摘要】：Al-Si-Cu合金具有良好的流動性能、密度低、熱穩(wěn)定性好、耐磨等優(yōu)點,常作為鑄造鋁合金廣泛應(yīng)用于汽車、輪船、軍工等領(lǐng)域。但是鑄造鋁合金普遍韌性較差,為進一步提高合金韌性,本文以ADC12壓鑄鋁合金為研究對象,分別單獨添加0-2%的稀土 Y、Ce和Nd,對ADC12合金進行變質(zhì)細化及進行后續(xù)的熱處理;降低Cu和Fe含量、略微提高Mn和 Mg 含量,制備 Al-xSi-0.55Cu-0.85 Y-0.45Mn-0.45Mg-0.35Fe(x=7.5, 8.5, 9.5 wt%)合金。采用ICP、XRD、OM和SEM進行相組成和組織分析,萬能材料拉伸試驗機、螺旋流動模具和沖擊試驗機對比合金的室/高溫拉伸力學(xué)性能、流動性能和沖擊韌性,從而確定最佳的合金化元素類型、含量和熱處理工藝參數(shù),建立合金成分與組織、性能之間的內(nèi)在關(guān)系,為高韌性壓鑄鋁合金的開發(fā)提供理論依據(jù)。主要結(jié)果如下:(1) ADC12-xRE 合金由 α-Al、共晶 Si、Al_2Cu、Al_8SiFe2相及 Al-RE 相組成。Y、Ce和Nd三種稀土元素對ADC12合金具有一定的變質(zhì)效果,變質(zhì)效果為Y最佳,Ce次之,Nd最差。當(dāng)Y為0.85 %時,ADC12合金變質(zhì)效果最佳,合金鑄態(tài)組織細化最顯著。不僅使初生α-Al由粗大樹枝晶轉(zhuǎn)變?yōu)榧毿“麪罹Ш偷容S晶,而且使針狀共晶Si轉(zhuǎn)變?yōu)榧毿±w維狀或顆粒狀,分布更均勻,等軸晶和顆粒狀的共晶Si硅數(shù)目大大增加,同時生成Al3Y新相;此時合金的鑄態(tài)流動長度、室溫抗拉強度、伸長率和沖擊韌性分別為1541mm,225 MPa,3.5%和10.8J/cm2,而鑄態(tài)ADC2合金流動長度、室溫抗拉強度、長率和沖擊韌性分別為 1287 mm,188 MPa, 1.5 %和 3.8 J/cm2。(2)經(jīng)過520℃保溫8 h熱處理后,ADC12合金的組織被細化,抗拉強度為205 MPa,伸長率為1.5%,沖擊韌性為7.4 J/cm2;而ADC12-0.85Y合金組織中共晶硅相顆粒發(fā)生長大,抗拉強度降低,伸長率提高,沖擊韌性大幅提高,與鑄態(tài)ADC12-0.85Y合金相比,材料韌性顯著提高。(3) Al-8.5Si-0.55Cu-0.85Y-0.45Mn-0.45Mg-0.35Fe 合金組織均勻,部分 Al 基體由枝晶狀轉(zhuǎn)變?yōu)榈容S晶,短棒狀共晶Si增加。合金具有優(yōu)異的流動性能,但抗拉強度和伸長率分別為189 MPa和2.0 %,其綜合力學(xué)性能不及ADC12-0.85Y合金。
[Abstract]:Al-Si-Cu alloy has many advantages such as good fluidity, low density, good thermal stability, wear resistance and so on. It is widely used as casting aluminum alloy in automobile, ship, military industry and so on. But the general toughness of cast aluminum alloy is poor. In order to further improve the toughness of cast aluminum alloy, this paper takes ADC12 die casting aluminum alloy as the research object, separately adding 0-2% rare earth YCe and Nd, respectively. The ADC12 alloy was modified and refined and followed by heat treatment. The content of Cu and Fe was decreased, the content of Mn and Mg was increased slightly, and Al-xSi-0.55Cu-0.85 Y-0.45Mn-0.45Mg-0.35Fe (x _ 2O _ 7.5, 8.5, 9.5 wt%) alloys were prepared. The phase composition and microstructure of the alloy were analyzed by ICP,XRD,OM and SEM. The tensile mechanical properties, fluidity and impact toughness of the alloy at room / high temperature were compared between the universal material tensile tester, the spiral flow mould and the impact tester. Thus the optimum alloying element type, content and heat treatment process parameters are determined, and the internal relationship between alloy composition, microstructure and properties is established, which provides a theoretical basis for the development of high toughness die casting aluminum alloy. The main results are as follows: (1) the ADC12-xRE alloy is composed of 偽-Al, eutectic Si,Al_2Cu,Al_8SiFe2 phase and Al-RE phase. YCe and Nd have a certain modification effect on ADC12 alloy, and the modification effect is the best. Ce was second, Nd was the worst. When Y is 0.85%, the modification effect of ADC12 alloy is the best, and the microstructure refinement of the alloy is the most obvious. Not only the primary 偽-Al is changed from coarse dendrite to fine cellular crystal and equiaxed crystal, but also acicular eutectic Si is transformed into fine fibrous or granular, the distribution is more uniform, and the number of equiaxed and granular eutectic Si silicon is greatly increased. At the same time, the new phase of Al3Y was formed. The flow length, tensile strength, elongation and impact toughness of the as-cast ADC2 alloy were 1 541 mm / 225 MPa,3.5% and 10.8 J / cm 2, respectively, while the flow length, room temperature tensile strength, length ratio and impact toughness of the as-cast ADC2 alloy were 1287 mm, respectively. After heat treatment at 520 鈩，

本文編號：2306211