本文關(guān)鍵詞： 混合稀土 鋁合金 流動(dòng)性 T6熱處理 摩擦磨損　出處：《南昌大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：作為一種Al-Si合金,ADC12鋁合金具有良好的鑄造性能,在國民經(jīng)濟(jì)中得到了廣泛應(yīng)用。然而,其鑄態(tài)顯微組織含有大量粗大的初生α-Al枝晶以及長針狀的共晶硅相,嚴(yán)重的降低了合金的性能。此外,在熔煉過程中也會(huì)引入較多的鐵等雜質(zhì)。因此,通過研究控制合金中這些相的大小和形貌來改善合金性能非常有必要。為此,本文通過向ADC12合金中添加高能間歇超聲法制備的Al-5La-5Yb中間合金,探討混合稀土(La+Yb)對(duì)鋁合金組織及性能的影響。結(jié)果表明:混合稀土(La+Yb)的加入可以明顯地細(xì)化組織中α-Al枝晶和共晶硅,改善有害β-Al5FeSi相。α-Al二次枝晶臂間距、平均直徑和平均晶胞面積顯著減小,晶粒排列整齊,取向趨于一致;粗大的針狀或板條狀共晶硅細(xì)化成彌散分布的短棒狀或顆粒狀;長針狀或板條狀β-Al5FeSi相形貌得到極大改善。當(dāng)添加0.6wt.%的混合稀土?xí)r,變質(zhì)效果最明顯�；旌舷⊥�(La+Yb)可以極大地提高合金機(jī)械性。合金抗拉強(qiáng)度、延伸率、彈性模量和硬度均隨著稀土加入量的增加而提高,當(dāng)加入量為0.6wt.%時(shí)達(dá)到最高值,此時(shí)抗拉強(qiáng)度275.40 Mpa、延伸率4.92%、彈性模量73.09 GPa及硬度117 HV,相對(duì)基體分別提高了92.4%、132.1%、6.42%、29.8%�；旌舷⊥�(La+Yb)的加入可以顯著改善ADC12鋁合金的流動(dòng)性。合金流動(dòng)性與稀土添加量存在二次函數(shù)關(guān)系,最佳稀土添加量為0.52wt.%,而這個(gè)最佳值與澆注溫度的關(guān)系不大。添加不同含量稀土?xí)r,加入量為0.6wt.%條件下ADC12鋁合金流動(dòng)性對(duì)澆注溫度的敏感性最高。合金流動(dòng)性隨著澆注溫度的升高而增加,存在近似Lf=7.943Tp-4750.783的直線型關(guān)系,可以適當(dāng)提高合金澆注溫度來改善流動(dòng)性。經(jīng)過T6熱處理,合金組織得到顯著改善,共晶硅由固溶處理前的長針狀細(xì)化成小顆粒狀或圓質(zhì)點(diǎn),長針狀β-Al5FeSi相也變得短小細(xì)化,甚至轉(zhuǎn)化成古漢字筆畫狀的α-Al8Fe2Si相。添加一定量的稀土,時(shí)效析出顆粒狀A(yù)l2Cu強(qiáng)化相。T6熱處理后,合金力學(xué)性能提高,塑性改善。添加不同含量的稀土,合金性能表現(xiàn)出先增大后減小的趨勢(shì)。當(dāng)添加0.6wt.%的混合稀土?xí)r,組織改善最佳,力學(xué)性能達(dá)最佳,塑性最好,抗拉強(qiáng)度與延伸率分別達(dá)到312.56 MPa、3.86%,相對(duì)熱處理態(tài)基體分別提高了69.35%、113.26%�；旌舷⊥�(La+Yb)和熱處理均可明顯地改善ADC12合金的耐磨性,質(zhì)量磨損率和摩擦系數(shù)大大下降。隨著稀土添加量的增加,合金的質(zhì)量磨損率和摩擦系數(shù)均表現(xiàn)為先減少而增加的趨勢(shì),摩擦系數(shù)波動(dòng)穩(wěn)定。當(dāng)混合稀土添加量達(dá)0.6wt.%時(shí),鑄態(tài)合金耐磨性最好,質(zhì)量磨損率和摩擦系數(shù)分別下降到4.42%和0.30,相對(duì)基體分別減少了29.95%和23.1%。T6熱處理后,質(zhì)量磨損率和摩擦系數(shù)分別下降到0.43%和0.26,相對(duì)熱處理基體分別減少了67.2%和25.7%,相對(duì)鑄態(tài)稀土合金分別下降了90.3%和33.3%。鑄態(tài)基體合金表現(xiàn)出疲勞磨損的機(jī)制,T6熱處理態(tài)基體則為氧化磨損機(jī)制;添加稀土后,鑄態(tài)和T6態(tài)合金均表現(xiàn)出以磨粒磨損為主的磨損機(jī)制。
[Abstract]:As a kind of Al-Si alloy, ADC12 Aluminum Alloy has good casting properties, has been widely used in the national economy. However, the microstructures contain a large number of coarse primary alpha -Al dendrite and long acicular eutectic silicon phase, seriously reduce the performance of the alloy. In addition, iron and other impurities in the melting the process will also introduce more. Therefore, through the study of these phases in the alloy to control the size and morphology to improve the properties of the alloy is very necessary. Therefore, this article by adding Al-5La-5Yb master alloy prepared by intermittent high-energy ultrasound to ADC12 alloy, explore the mixed rare earth (La+Yb) and the influence on the performance of Aluminum Alloy organization. The results indicate that the mixed rare earth (La+Yb) could obviously refine alpha -Al dendrite and eutectic silicon, improve the harmful phase. Alpha -Al beta -Al5FeSi two dendrite arm spacing, average diameter and average cell area was significantly reduced, crystal The particle arranged to have the same orientation; acicular or lath coarse eutectic silicon refinement into dispersed rod like or granular; long needle or plate strip beta -Al5FeSi morphology has been greatly improved. When the mixed addition of rare earth 0.6wt.%, the most obvious modification effect. The mixed rare earth (La+Yb) can greatly improve the mechanical alloy. The tensile strength, elongation, elastic modulus and hardness were increased with increasing amount of rare earth, when adding to 0.6wt.% reached the highest value at 275.40 Mpa, tensile strength, elongation 4.92%, elastic modulus and hardness of 117 HV, 73.09 GPa, relative to the substrate were increased by 92.4%, 132.1%, 6.42%, 29.8%. mixed rare earth (La+Yb) liquidity could significantly improve the ADC12 Aluminum Alloy. There are quadratic function relationship between the fluidity of the alloy and rare earth content, the optimum adding amount of rare earth 0.52wt.%, and the best value and casting Little relation to temperature. Adding different content of rare earth, adding liquidity ADC12 Aluminum Alloy 0.6wt.% under the condition of pouring temperature was the highest. The fluidity of the alloy increases with the increase of the pouring temperature, there is a linear relationship between the Lf=7.943Tp-4750.783 type approximation, can improve the fluidity of increasing casting temperature of the alloy after T6 heat treatment. The microstructure of the alloy has been significantly improved, the eutectic silicon by solid solution refinement before long needle into small granular or circular particle, long needle like -Al5FeSi phase becomes short beta refinement, even transformed into a -Al8Fe2Si shape. The ancient Chinese characters strokes to add a certain amount of rare earth, precipitation granular Al2Cu.T6 phase after heat treatment. To improve the mechanical properties of the alloy, plastic improved. Adding different content of rare earth alloy, performance showed first increased and then decreased. When the mixed addition of rare earth 0.6wt.%, improve the organization The best mechanical properties was the best, the best plastic tensile strength and elongation were respectively 312.56 MPa, 3.86%, relative heat treatment state matrix were increased by 69.35%, 113.26%. rare earth (La+Yb) resistance and heat treatment can obviously improve the quality of ADC12 alloy, the wear rate and friction coefficient decreased greatly with increasing. The amount of rare earth alloy, the mass wear rate and friction coefficient were decreased and increased, the friction coefficient stability. When the mixed rare earth content was 0.6wt.%, the wear resistance of the cast alloy the best quality, the wear rate and friction coefficient are decreased by 4.42% and 0.30, relative to the matrix were reduced by 29.95% and 23.1%.T6 after heat treatment, the quality of the wear rate and friction coefficient are decreased by 0.43% and 0.26, the relative heat treatment matrix were reduced by 67.2% and 25.7%, relatively rare earth alloy as cast cast were decreased by 90.3% and 33.3%. The matrix alloy shows fatigue wear mechanism, and the T6 heat treated matrix is the mechanism of oxidation wear. After adding rare earth, the wear mechanism of the as cast and T6 alloy shows abrasive wear.

【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG146.21

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本文編號(hào)：1451494