本文選題：鎂合金　切入點(diǎn)：旋轉(zhuǎn)磁場(chǎng)　出處：《沈陽工業(yè)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：電磁攪拌技術(shù)對(duì)鎂合金具有細(xì)化晶粒、改善力學(xué)性能的作用,但不同攪拌參數(shù)下鎂合金的組織和性能存在較大的差異。本文以Mg-Al-Zn系鎂合金為實(shí)驗(yàn)材料,在不同攪拌參數(shù)下(改變攪拌頻率和磁場(chǎng)電流)澆注鎂合金管坯,研究旋轉(zhuǎn)磁場(chǎng)對(duì)鎂合金顯微組織和力學(xué)性能的影響。并采用Ansoft和Fluent軟件順序耦合的方法對(duì)電磁攪拌作用下鎂合金凝固過程的電磁場(chǎng)、溫度場(chǎng)進(jìn)行數(shù)值模擬,研究電磁攪拌參數(shù)對(duì)磁場(chǎng)和溫度場(chǎng)的影響規(guī)律。研究結(jié)果表明:一個(gè)周期內(nèi)旋轉(zhuǎn)磁場(chǎng)在不同時(shí)刻的分布規(guī)律相同,且旋轉(zhuǎn)周期與電流變化周期相同。隨著磁場(chǎng)電流增大,產(chǎn)生的最大磁感應(yīng)強(qiáng)度和最大電磁力逐漸增大;隨著攪拌頻率增大,產(chǎn)生的最大磁感應(yīng)強(qiáng)度逐漸減小,而作用于熔體的最大電磁力逐漸增大。不同攪拌參數(shù)下,沿著半徑方向,磁感應(yīng)強(qiáng)度先減小后增大,電磁力逐漸增大。電磁攪拌改變了金屬液的換熱條件,使鎂合金溶液凝固過程溫度變化趨于均勻。當(dāng)攪拌頻率6Hz時(shí),磁場(chǎng)電流分別為90A、120A、150A條件下對(duì)應(yīng)的過冷度為2.5℃、4℃、4.5℃,磁場(chǎng)電流越大,AZ31鎂合金溶液冷卻速度越快越有利于增加形核率,逐漸細(xì)化晶粒。當(dāng)磁場(chǎng)電流150A時(shí),攪拌頻率分別為6Hz、8Hz、10Hz條件下對(duì)應(yīng)的過冷度為4℃、5℃、6.5℃,攪拌頻率越大,AZ91鎂合金溶液冷卻速度越快,同樣有利于增加形核率,逐漸細(xì)化晶粒。磁場(chǎng)電流越大或攪拌頻率越大,晶粒細(xì)化效果越好,且磁場(chǎng)電流為150A時(shí),AZ31鎂合金晶粒內(nèi)部產(chǎn)生了較多的孿晶,可以提高合金的抗拉強(qiáng)度和屈服強(qiáng)度;β-Mg17Al12相逐漸溶解到α-Mg基體中,形成細(xì)小的第二相,并增加了Al原子在基體中的固溶度,可以提高合金的伸長(zhǎng)率。磁場(chǎng)電流越大或攪拌頻率越大,鎂合金的力學(xué)性能越好。磁場(chǎng)電流150A時(shí),AZ31鎂合金抗拉強(qiáng)度為194MPa,屈服強(qiáng)度為89MPa,伸長(zhǎng)率為14.8%,與自然凝固狀態(tài)相比分別提高23.6%、20.3%和57.5%。攪拌頻率10Hz時(shí),AZ91鎂合金抗拉強(qiáng)度為164MPa,屈服強(qiáng)度為99MPa,伸長(zhǎng)率為5.1%,與自然凝固狀態(tài)相比分別提高21.5%、19.3%、41.7%。
[Abstract]:Electromagnetic stirring technology can refine the grain and improve the mechanical properties of magnesium alloys, but the microstructure and properties of magnesium alloys under different stirring parameters have great differences. In this paper, Mg-Al-Zn series magnesium alloys are used as experimental materials. Casting magnesium alloy tube billets with different stirring parameters (varying stirring frequency and magnetic field current), The effect of rotating magnetic field on microstructure and mechanical properties of magnesium alloy was studied. The electromagnetic field and temperature field of magnesium alloy solidified by electromagnetic stirring were numerically simulated by Ansoft and Fluent software sequential coupling method. The effect of electromagnetic stirring parameters on magnetic field and temperature field is studied. The results show that the distribution of rotating magnetic field is the same at different times in a period, and the rotation period is the same as the period of current variation. With the increase of stirring frequency, the maximum magnetic induction intensity decreases gradually, while the maximum electromagnetic force acting on the melt increases gradually. Under different stirring parameters, the maximum magnetic induction intensity increases along the radius direction. The magnetic induction intensity decreases first and then increases, and the electromagnetic force increases gradually. Electromagnetic stirring changes the heat transfer condition of molten metal and makes the temperature change of magnesium alloy solution more uniform. When the stirring frequency is 6 Hz, the temperature change of magnesium alloy solution is uniform. The corresponding undercooling degree is 2.5 鈩，

本文編號(hào)：1580313