發(fā)布時間：2018-04-22 01:15

  本文選題：ZK60鎂合金 + 電脈沖處理��； 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：隨著能源危機的日益嚴峻,環(huán)境惡化的不斷加劇,人類社會越來越注重輕量化,綠色化制造。作為一種新型的環(huán)保材料,鎂合金因其密度低、比強度高、減震性好、機加工性能優(yōu)良、易回收等優(yōu)點,廣泛應(yīng)用于航空航天、汽車、3C產(chǎn)品等諸多領(lǐng)域。但由于受材料制備、加工技術(shù)、抗腐蝕性能等因素的制約,鎂合金的發(fā)展?jié)摿εc實際應(yīng)用的現(xiàn)狀之間存在巨大差異。在此背景下,對鎂合金的研究在為拓寬鎂的應(yīng)用市場,緩解能源危機方面有著重要的戰(zhàn)略意義。本文利用高能脈沖電流處理20%和60%兩種變形量的ZK60鎂合金,通過調(diào)節(jié)電脈沖頻率、脈寬、處理時間等實驗參數(shù),使變形鎂合金在較低溫度下發(fā)生靜態(tài)再結(jié)晶,并通過表征結(jié)果和理論計算兩方面對電脈沖處理過程中產(chǎn)生的熱效應(yīng)和非熱效應(yīng)、再結(jié)晶過程中的形核與長大以及再結(jié)晶機理進行了分析。結(jié)果表明,電脈沖處理能夠細化變形鎂合金的微觀組織從而提高其綜合力學(xué)性能。ZK60鎂合金的晶粒尺寸由鑄態(tài)的150μm細化到4μm,抗拉強度提高了52.3%,伸長率提高了105%,EBSD分析表明處理后的試樣織構(gòu)強度顯著減弱。此外,通過理論計算發(fā)現(xiàn),脈沖電流為鎂合金的再結(jié)晶提供了額外的吉布斯自由能,降低了再結(jié)晶形核的能量勢壘,提高了再結(jié)晶形核率并顯著細化再結(jié)晶組織。對比實驗數(shù)據(jù)得知,與傳統(tǒng)熱處理方法相比,電脈沖處理能夠在較低的溫度下完成再結(jié)晶,再結(jié)晶晶粒長大趨勢較小,從而得到更加細小均勻的顯微組織。探究對比了不同變形量的ZK60鎂合金在脈沖處理過程中的再結(jié)晶形核機理,不同變形量的ZK60鎂合金在脈沖處理過程中的形核方式有很大差異。小變形量試樣主要在晶界處形核,而原晶粒內(nèi)部幾乎無新晶核出現(xiàn),主要發(fā)生回復(fù),形成較為粗大不均勻的組織;而大變形量試樣由于變形均勻,絕大部分區(qū)域在脈沖處理初期就形成了大角度晶界,從而發(fā)生形核和長大,形成細小均勻的再結(jié)晶組織。
[Abstract]:With the increasingly severe energy crisis and the worsening of environment, human society pays more and more attention to lightweight and green manufacturing. As a new kind of environmental protection material, magnesium alloy is widely used in many fields such as aerospace, automobile and 3C products, because of its low density, high specific strength, good shock absorption, good machinability, easy recovery and so on. However, due to the constraints of material preparation, processing technology, corrosion resistance and other factors, there is a great difference between the development potential of magnesium alloy and the current situation of practical application. In this context, the research on magnesium alloys has important strategic significance in broadening the application market of magnesium and alleviating the energy crisis. In this paper, ZK60 magnesium alloys with 20% and 60% deformations were treated with high energy pulse current. The static recrystallization of wrought magnesium alloys at low temperature was achieved by adjusting the experimental parameters such as frequency, pulse width and treatment time. The thermal and non-thermal effects, nucleation and growth during recrystallization and the mechanism of recrystallization were analyzed by means of both characterization results and theoretical calculations. The results show that Electrical pulse treatment can refine microstructure of wrought magnesium alloy and improve its comprehensive mechanical properties. The grain size of ZK60 magnesium alloy is refined from 150 渭 m to 4 渭 m in as-cast state, tensile strength is increased by 52.3% and elongation is increased by 105% EBSD analysis. The texture strength of the sample decreased significantly. In addition, it is found that pulse current provides additional Gibbs free energy for recrystallization of magnesium alloy, reduces the energy barrier of recrystallization nucleation, increases the rate of recrystallization nucleation and refines the recrystallization structure. Compared with the traditional heat treatment method, compared with the traditional heat treatment method, the electrical pulse treatment can complete recrystallization at lower temperature, and the recrystallization grain length trend is smaller, resulting in more fine and uniform microstructure. The mechanism of recrystallization nucleation of ZK60 magnesium alloys with different deformations during pulse treatment was studied and compared. The nucleation modes of ZK60 magnesium alloys with different deformations were very different during pulse treatment. The small deformation samples nucleate mainly at grain boundaries, but there is almost no new nucleation in the original grains, which mainly restores to form a coarse and uneven structure, while the large deformation samples are homogeneous due to deformation. Large angle grain boundaries were formed in most of the regions at the early stage of pulse processing, which resulted in nucleation and growth, resulting in fine and uniform recrystallization structure.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.22

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