發(fā)布時間：2018-01-16 20:13

  本文關(guān)鍵詞：鑄造Al-Si合金中稀土與硼的組織調(diào)控作用及對性能的影響　出處：《東南大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 鑄造鋁硅合金 稀土元素 晶粒細(xì)化 顯微組織 力學(xué)性能

【摘要】：本文以鑄造Al-Si系合金為研究對象,通過添加微量稀土元素La和元素B,綜合采用OM、SEM、TEM等組織觀察、凝固過程熱分析和拉伸測試等分析手段,探究La和B對合金微觀組織及拉伸性能的影響。在Al-11Si合金中添加Ti、La、B及Sr四種元素,并改變元素的添加順序,考察了Ti、La、B、Sr之間的交互作用對合金鑄態(tài)組織及拉伸性能的影響。結(jié)果表明,在0.02wt.%Sr變質(zhì)的Al-11Si合金中,進(jìn)一步添加0.05wt.%B,會使共晶Si由細(xì)小的纖維狀轉(zhuǎn)變?yōu)榇执蟮陌迤瑺?Sr所引起的IIT機(jī)制被抑制,共晶Si以TPRE機(jī)制生長,即引起了 Sr、B毒化。Ti可以解除Sr、B毒化,使得共晶Si生長由TPRE機(jī)制再次轉(zhuǎn)變?yōu)镮IT機(jī)制,共晶Si形貌相應(yīng)地由粗大的板片狀轉(zhuǎn)變?yōu)榧?xì)小、均勻的纖維狀,從而顯著提高合金的延伸率。La同樣可以解除Sr、B毒化,只是這種解除毒化的作用還取決于元素的添加順序,與此同時,La的添加還可以使合金的α-Al枝晶得到顯著的細(xì)化。以近共晶及過共晶Al-Si合金為研究對象,考察了 B單獨(dú)添加及La、B聯(lián)合添加對合金中Si相的影響。結(jié)果表明,在未經(jīng)變質(zhì)的Al-Si合金中添加B可以促進(jìn)Si相的形核,并使得共晶Si中孿晶發(fā)生單方向的增殖,促進(jìn)共晶Si的不斷分枝,從而導(dǎo)致共晶區(qū)擴(kuò)大,且使得共晶Si由粗大的片狀轉(zhuǎn)變?yōu)楦鼮槊芗�、�?xì)小的片狀。LaB6相的密排面{110}與Si相的密排面{111}之間具有良好的晶體學(xué)位相關(guān)系,LaB6可能作為Si相的形核基底促進(jìn)Si相的形核。LaB6相與富Fe相之間在多對原子面上均存在著良好的晶體學(xué)匹配關(guān)系,因而LaB6可能作為富Fe相的形核基底促進(jìn)富Fe相的形核,進(jìn)而富Fe相作為Si相的異質(zhì)形核核心促進(jìn)Si相的形核。利用熔體反應(yīng)原位合成法,使用工業(yè)純鋁,A1-3B和Al-10La中間合金制備了Al-2La-1B中間合金。在金屬型澆注的條件下,Al-2La-1B中間合金可以對Al-7Si、Al-11Si合金以及ZL101合金進(jìn)行有效細(xì)化,但不能細(xì)化ZL101A合金;在砂型澆注的條件下,Al-2La-1B中間合金不能有效細(xì)化ZL101A合金,而能有效細(xì)化ZL104合金,并提升ZL104合金的鑄態(tài)拉伸性能。在Al-11 Si-1.2La-0.6B合金中添加足量的Ti,可以置換LaB6中的La而生成TiB2,La在隨后的凝固過程中以富La化合物的形式析出。
[Abstract]:In this paper, the cast Al-Si alloy was studied. The microstructure of the cast Al-Si alloy was observed by adding trace rare earth element La and element B, etc. The effect of La and B on the microstructure and tensile properties of Al-11Si alloy was investigated by means of thermal analysis and tensile test. The effect of the interaction between Ti-Li La-B-Sr on the as-cast microstructure and tensile properties of the alloy was investigated by changing the addition order of the elements. The addition of 0.05wt.B to the Al-11Si alloy modified by 0.02wt.and Sr can change the eutectic Si from fine fibrous to coarse lamellar. Sr-induced IIT mechanism was inhibited, and eutectic Si was grown by TPRE mechanism, which caused SrB poisoning. The growth of eutectic Si was changed from TPRE mechanism to IIT mechanism, and the morphology of eutectic Si changed from coarse sheet to fine and uniform fiber. Thus, the elongation of the alloy. La can also be detoxified, but the effect of this detoxification also depends on the addition order of elements, at the same time. The addition of La can also refine the dendrite of 偽 -Al. Taking the near eutectic and hypereutectic Al-Si alloys as research objects, the addition of B and La were investigated. The results show that the addition of B to the unmodified Al-Si alloy can promote the nucleation of Si phase and make the twin in eutectic Si propagate in one direction. It promotes the continuous branching of eutectic Si, which results in the enlargement of eutectic region and the transition of eutectic Si from coarse flake to more dense. There is a good crystal degree phase relationship between the compact plane {110} and the dense plane {111} of the small lamellar 路LaB6 phase. LaB6 may act as the nucleation substrate of Si phase to promote the nucleation of Si phase. There is a good crystallographic matching relationship between Fe rich phase and Fe rich phase. Therefore, LaB6 may be used as the nucleation substrate of Fe-rich phase to promote the nucleation of Fe-rich phase, and then Fe-rich phase as the heterogeneous nucleation core of Si phase to promote the nucleation of Si phase. The melt reaction in-situ synthesis method is used. The Al-2La-1B master alloy was prepared by using industrial pure aluminum alloy A1-3B and Al-10La master alloy. Al-2La-1B master alloy can refine Al-7Si-Al-11Si alloy and ZL101 alloy effectively, but it can not refine ZL101A alloy. The Al-2La-1B master alloy can not refine ZL101A alloy effectively, but can refine ZL104 alloy effectively under the condition of sand mold pouring. The as-cast tensile properties of ZL104 alloy were improved. Adding sufficient amount of Ti to Al-11 Si-1.2La-0.6B alloy, La in LaB6 could be replaced to form TiB2. La precipitates in the form of La-rich compounds during subsequent solidification.
【學(xué)位授予單位】：東南大學(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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