高性能過共晶Al-Si-Cu-Mg合金組織與性能的研究
發(fā)布時間：2019-06-22 08:43
【摘要】：過共晶Al-Si-Cu-Mg合金具有比強度高、硬度高、線膨脹系數(shù)小、耐磨性好、熱穩(wěn)定性好等特點,是一種理想的汽車發(fā)動機活塞材料。常規(guī)的重力鑄造過共晶Al-Si-Cu-Mg合金中粗大的初生Si和片層狀的共晶Si對基體有割裂作用,影響合金的性能。因此改變共晶Si和初生Si的形貌進(jìn)而提高合金性能成為國內(nèi)外過共晶Al-Si-Cu-Mg合金在應(yīng)用方面的研究重點。本文利用變質(zhì)處理、合金化、擠壓鑄造和熱處理等方法改善合金的顯微組織,進(jìn)而提高合金的力學(xué)性能。對過共晶Al-Si-Cu-Mg合金進(jìn)行變質(zhì)處理和合金化,研究變質(zhì)處理和合金化對合金的顯微組織及力學(xué)性能的影響。研究表明,Sr的加入使合金組織中的粗大片狀共晶Si變?yōu)榧?xì)小的纖維狀,對擠壓鑄造合金進(jìn)行變質(zhì)處理時,隨著P的加入原本擠壓鑄造時細(xì)小塊狀的初生Si反而長大,合金的抗拉強度及伸長率明顯降低,主要是形成的Al-Sr-P影響了變質(zhì)效果。Sr變質(zhì)的擠壓鑄造合金的力學(xué)性能較好,抗拉強度為203.67MPa、伸長率為2.95%、硬度113.13HB。Ni、Cr和Mo的加入可以提高合金的力學(xué)性能,改善了過共晶Al-Si-Cu-Mg合金的顯微組織,合金中的Al-Si-Mn-Fe多元相由花瓣狀轉(zhuǎn)變?yōu)榱钋覐浬⒎植加诨w中,阻礙位錯的運動,對基體有一定的釘扎作用。合金化的合金的抗拉強度為231.50MPa、伸長率為2.86%、硬度124.10HB。擠壓鑄造選取了398MPa、598MPa、796MPa三個不同的擠壓力。隨著比壓增加,初生Si相尺寸逐漸變小后逐漸消失;共晶Si相也得到明顯細(xì)化,分布均勻,組織中α-Al枝晶明顯增加,越來越發(fā)達(dá)。擠壓鑄造比壓為598MPa時,力學(xué)性能最好,合金抗拉強度為231.50MPa,伸長率為2.68%,硬度為124.10HB。研究熱處理對擠壓鑄造Al-17.5Si多元合金顯微組織及力學(xué)性能的影響。分別改變固溶處理溫度和固溶處理時間,Si相在尖端、凹槽處逐漸溶解、�；�,塊狀初生Si相逐漸細(xì)化,球化,棱角和尖端鈍化,溫度過高或時間過長時Si相出現(xiàn)粗化現(xiàn)象。同時熱處理過程中析出的Al2Cu、AlNi相等也發(fā)生明顯改變,多元合金相在熱處理時發(fā)生消融現(xiàn)象,減小對基體的割裂作用,熱處理對Al-Si-Cu-Mg摩擦磨損性能有較大影響,提高了合金的耐磨性。熱處理1h和12h合金力學(xué)性能較好,抗拉強度達(dá)到274.5MPa和286.67MPa,硬度達(dá)到了130.63HB和144.07HB,伸長率達(dá)到4.00%和4.32%,且磨損量相近。
[Abstract]:Hypereutectic Al-Si-Cu-Mg alloy is an ideal piston material for automobile engine because of its high specific strength, high hardness, low linear expansion coefficient, good wear resistance and good thermal stability. The coarse primary Si and lamellar eutectic Si in the conventional gravity casting hypereutectic Al-Si-Cu-Mg alloy have cutting effect on the matrix and affect the properties of the alloy. Therefore, changing the morphology of eutectic Si and primary Si to improve the properties of hypereutectic Al-Si-Cu-Mg alloys at home and abroad has become the focus of application. In this paper, modification, alloying, squeeze casting and heat treatment are used to improve the microstructure of the alloy, and then the mechanical properties of the alloy are improved. The hypereutectic Al-Si-Cu-Mg alloy was modified and alloyed, and the effect of modification and alloying on the microstructure and mechanical properties of the alloy was studied. The results show that the coarse sheet eutectic Si in the microstructure of the alloy becomes fine fiber with the addition of Sr. When the squeeze casting alloy is modified, the primary Si of the fine block grows with the addition of P, and the tensile strength and extension of the alloy decrease obviously, mainly because the Al-Sr-P formed affects the modification effect. The mechanical properties of the squeeze casting alloy modified by Sr are better. The tensile strength is 203.67 MPA, the extension is 2.95%, and the hardness is 113.13 HB.Ni. the addition of Cr and Mo can improve the mechanical properties of the alloy and improve the microstructure of hypereutectic Al-Si-Cu-Mg alloy. The Al-Si-Mn-Fe multicomponent phase in the alloy changes from petal to grain and is dispersed in the matrix, which hinders the movement of dislocation and has a certain pinning effect on the matrix. The tensile strength, extension and hardness of the alloyed alloy are 231.50MPA, 2.86% and 124.10HB respectively. 398 MPA, 598 MPA and 796 MPA were selected for squeeze casting. With the increase of specific pressure, the size of primary Si phase gradually decreases and then disappears, the eutectic Si phase is also obviously refined and evenly distributed, and the 偽-Al dendrite in the microstructure increases obviously and becomes more and more developed. When the specific pressure of squeeze casting is 598MPa, the mechanical properties of the alloy are the best. The tensile strength of the alloy is 231.50 MPA, the elongation is 2.68%, and the hardness is 124.10 HB. The effect of heat treatment on microstructure and mechanical properties of squeeze casting Al-17.5Si multicomponent alloy was studied. When the solid solution treatment temperature and solid solution treatment time are changed respectively, the Si phase is gradually dissolved and granulated at the tip, the groove is gradually dissolved, the bulk primary Si phase is gradually refined, the spheroidizing, angular and tip passivation, and the coarsening of Si phase occurs when the temperature is too high or the time is too long. At the same time, the equality of Al2Cu,AlNi precipitated in the process of heat treatment also changed obviously, and the multicomponent alloy phase melted during heat treatment, which reduced the cutting effect on the matrix. Heat treatment had a great influence on the friction and wear properties of Al-Si-Cu-Mg, and improved the wear resistance of the alloy. The mechanical properties of the alloy are good at 1 h and 12 h after heat treatment, the tensile strength is up to 274.5MPa and 286.67 MPA, the hardness is up to 130.63HB and 144.07 HB, the elongation is 4.00% and 4.32%, and the wear rate is similar.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.21
本文編號：2504416
[Abstract]:Hypereutectic Al-Si-Cu-Mg alloy is an ideal piston material for automobile engine because of its high specific strength, high hardness, low linear expansion coefficient, good wear resistance and good thermal stability. The coarse primary Si and lamellar eutectic Si in the conventional gravity casting hypereutectic Al-Si-Cu-Mg alloy have cutting effect on the matrix and affect the properties of the alloy. Therefore, changing the morphology of eutectic Si and primary Si to improve the properties of hypereutectic Al-Si-Cu-Mg alloys at home and abroad has become the focus of application. In this paper, modification, alloying, squeeze casting and heat treatment are used to improve the microstructure of the alloy, and then the mechanical properties of the alloy are improved. The hypereutectic Al-Si-Cu-Mg alloy was modified and alloyed, and the effect of modification and alloying on the microstructure and mechanical properties of the alloy was studied. The results show that the coarse sheet eutectic Si in the microstructure of the alloy becomes fine fiber with the addition of Sr. When the squeeze casting alloy is modified, the primary Si of the fine block grows with the addition of P, and the tensile strength and extension of the alloy decrease obviously, mainly because the Al-Sr-P formed affects the modification effect. The mechanical properties of the squeeze casting alloy modified by Sr are better. The tensile strength is 203.67 MPA, the extension is 2.95%, and the hardness is 113.13 HB.Ni. the addition of Cr and Mo can improve the mechanical properties of the alloy and improve the microstructure of hypereutectic Al-Si-Cu-Mg alloy. The Al-Si-Mn-Fe multicomponent phase in the alloy changes from petal to grain and is dispersed in the matrix, which hinders the movement of dislocation and has a certain pinning effect on the matrix. The tensile strength, extension and hardness of the alloyed alloy are 231.50MPA, 2.86% and 124.10HB respectively. 398 MPA, 598 MPA and 796 MPA were selected for squeeze casting. With the increase of specific pressure, the size of primary Si phase gradually decreases and then disappears, the eutectic Si phase is also obviously refined and evenly distributed, and the 偽-Al dendrite in the microstructure increases obviously and becomes more and more developed. When the specific pressure of squeeze casting is 598MPa, the mechanical properties of the alloy are the best. The tensile strength of the alloy is 231.50 MPA, the elongation is 2.68%, and the hardness is 124.10 HB. The effect of heat treatment on microstructure and mechanical properties of squeeze casting Al-17.5Si multicomponent alloy was studied. When the solid solution treatment temperature and solid solution treatment time are changed respectively, the Si phase is gradually dissolved and granulated at the tip, the groove is gradually dissolved, the bulk primary Si phase is gradually refined, the spheroidizing, angular and tip passivation, and the coarsening of Si phase occurs when the temperature is too high or the time is too long. At the same time, the equality of Al2Cu,AlNi precipitated in the process of heat treatment also changed obviously, and the multicomponent alloy phase melted during heat treatment, which reduced the cutting effect on the matrix. Heat treatment had a great influence on the friction and wear properties of Al-Si-Cu-Mg, and improved the wear resistance of the alloy. The mechanical properties of the alloy are good at 1 h and 12 h after heat treatment, the tensile strength is up to 274.5MPa and 286.67 MPA, the hardness is up to 130.63HB and 144.07 HB, the elongation is 4.00% and 4.32%, and the wear rate is similar.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.21
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