本文選題：長周期有序堆垛結(jié)構(gòu) + Al合金化　； 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：鎂合金是當(dāng)今最輕的結(jié)構(gòu)金屬,具有優(yōu)良的機(jī)加工性能,阻尼減震性良好,比強(qiáng)度、比剛度高和可循環(huán)利用的優(yōu)點(diǎn),被譽(yù)為“21世紀(jì)發(fā)展前途最大的結(jié)構(gòu)金屬材料”,被廣泛應(yīng)用于交通運(yùn)輸,航空航天,消費(fèi)電子產(chǎn)品和計(jì)算機(jī)通訊等領(lǐng)域,是近年來國內(nèi)外材料界的研究熱點(diǎn)之一。稀土鎂合金因其高強(qiáng)性、高韌性、耐熱性好等突出特點(diǎn),在商用鎂合金領(lǐng)域占有重要地位。而長周期有序堆垛結(jié)構(gòu)(LPSO)的發(fā)現(xiàn),進(jìn)一步提高了稀土鎂合金的高溫性能和強(qiáng)韌性,國內(nèi)外學(xué)者針對長周期鎂合金進(jìn)行了廣泛的研究。本文通過常規(guī)鑄造制備了含有長周期相的Mg-Y-Zn-Mn-(Al)合金,該合金中生成了一種新的原位自生強(qiáng)化相。通過對鑄態(tài)合金進(jìn)行固溶處理和正擠壓變形處理,探究了固溶時(shí)間和冷卻方式以及擠壓速度對Mg-Y-Zn-Mn-Al合金微觀組織和力學(xué)性能的影響,同時(shí)探究了Al對18R和14H LPSO轉(zhuǎn)化的影響。除此以外還研究了不同狀態(tài)下Mg_(93.6)Y_(2.5)Zn_(2.5)Al_(0.4)合金的電化學(xué)腐蝕性能,以及富鈰混合稀土對Mg-Y-Zn-Mn-(Al)合金的變質(zhì)作用,主要研究結(jié)果如下:(1)Al能夠在一定程度上細(xì)化枝晶,減小枝晶臂間距;該合金元素的加入能夠在基體上生成新的Al(Y,Zn)_2相,起到復(fù)合強(qiáng)化的作用,添加量為0.4 at%時(shí),LPSO和Al(Y,Zn)_2相的比例達(dá)到最佳,鑄態(tài)下合金抗拉強(qiáng)度和伸長率達(dá)到259 MPa/5.4%。(2)固溶處理的最佳溫度為500℃,固溶處理后隨爐冷卻的合金,W相由網(wǎng)狀變?yōu)轭w粒狀;條狀18R-LPSO相固溶進(jìn)基體內(nèi)然后在冷卻過程中以精細(xì)的層片狀14H-LPSO相析出,同時(shí)在層片狀14H-LPSO之中夾著0.2μm左右的18R-LPSO相;Al(Y,Zn)_2相由固態(tài)下的點(diǎn)狀或針狀聚集長大,變?yōu)轸~骨狀。固溶處理后水淬的合金微觀組織因?yàn)槔鋮s速度太快,沒有精細(xì)層片狀14H-LPSO相析出,基體上只有細(xì)小的18R-LPSO相。(3)Al(Y,Zn)_2相對固溶處理時(shí)間十分敏感,固溶時(shí)間過長該相會(huì)發(fā)生聚集會(huì)導(dǎo)致組織惡化。固溶30 h時(shí)合金的力學(xué)性能最佳,抗拉強(qiáng)度和伸長率分別為257 MPa和15.4%。(4)正擠壓速率對Mg_(93.6)Y_(2.5)Zn_(2.5)Al_(0.4)合金中各相的形貌及動(dòng)態(tài)再結(jié)晶的數(shù)量和大小有顯著影響,速率為30mm/min中Al(Y,Zn)_2相得到充分碎化,分布最彌散,同時(shí)動(dòng)態(tài)再結(jié)晶的體積分?jǐn)?shù)最大。其力學(xué)性能最佳為375 MPa和17.5%。
[Abstract]:Magnesium alloy is the lightest structural metal with excellent machinability, good damping, high specific strength, high specific stiffness and recyclable utilization. It is called "the most promising structural metal material in the 21st century". It is widely used in the fields of transportation, aerospace, consumer electronics and computer communication. It is one of the research hotspots in the field of materials at home and abroad in recent years. Rare earth magnesium alloy plays an important role in commercial magnesium alloy field because of its high strength, high toughness and good heat resistance. The discovery of LPSO (long period ordered stacking structure) has further improved the high temperature properties and strength and toughness of rare earth magnesium alloys. Scholars at home and abroad have carried out extensive research on long period magnesium alloys. In this paper, Mg-Y-Zn-Mn-Al) alloy containing long period phase was prepared by conventional casting, and a new in-situ strengthening phase was formed in Mg-Y-Zn-Mn-Al) alloy. The effects of solution time, cooling mode and extrusion speed on the microstructure and mechanical properties of Mg-Y-Zn-Mn-Al alloy were investigated by solution treatment and forward extrusion treatment. The effects of Al on the transformation of 18R and 14H LPSO were also investigated. In addition, the electrochemical corrosion properties of mg _ S _ (93. 6) / Y _ S _ (2. 5) ~ (2. 5) / S _ (2.5) / S ~ (2 +) -AlN _ 4) alloy and the modification effect of cerium rich rare earth on Mg-Y-Zn-Mn-Al) alloy have been studied. The main results are as follows: (1) 1% Al can refine the dendrite to a certain extent and reduce the dendrite arm spacing; The addition of this alloy element can form a new phase of Al _ 2O _ Y _ O _ Zn _ T _ 2 on the matrix, which plays the role of compound strengthening. The ratio of LPSO and Al-YY _ (Zn) _ (2) is the best when the addition amount is 0.4 at%. The tensile strength and elongation of the as-cast alloy reached 259 MPA / 5.4. The optimum temperature of solution treatment was 500 鈩，

本文編號(hào)：1884550