發(fā)布時間：2018-11-09 17:49

【摘要】：鎂合金作為最輕的金屬結(jié)構(gòu)材料,廣泛應(yīng)用于汽車、航空航天及3C等領(lǐng)域,而鎂合金產(chǎn)品主要通過板材的形式使用。因此研制與開發(fā)短流程、大寬幅、高性能鎂合金板材受到人們廣泛關(guān)注。本文通過離心鑄造數(shù)值模擬與澆注,固溶處理,板材軋制及板材的退火處理,確定了一套合理的AZ91鎂合金板材成型工藝,研究過程如下:(1)通過計算機對離心鑄造制備長度為1500mm,外直徑為400mm,厚度為20mm的AZ91鎂合金管材的澆注過程進行流場及溫度場的模擬,分析得出:離心鑄造澆注過程中,合金液由澆口流入模具并向兩端流動,逐層充型,當澆注時間至8.4s時,第一層合金液首次充滿模具,20s時澆注過程結(jié)束;澆注過程中澆口部位合金液溫度最高,遠離澆口方向溫度逐漸降低,澆注結(jié)束時,管材兩端完全凝固,管材中心部位尚未凝固。(2)通過離心鑄造制備長度為1500mm,外直徑為400mm,厚度為20mm的AZ91鎂合金管材并確定離心鑄造工藝參數(shù)為:離心轉(zhuǎn)速900r/min,澆注溫度700℃,模具預熱溫度200℃;離心鑄造制備AZ91鎂合金管材外表面光滑平整,厚度均勻,充型完整,管材力學性能較鑄態(tài)有明顯提高,抗拉強度為158MPa,伸長率為3.4%。管材晶粒細小,分布均勻。(3)對離心鑄造AZ91鎂合金管材進行固溶處理,通過實驗分析得出:管材力學性能隨著固溶溫度的升高而提高,固溶溫度為415℃時力學性能達到最好,抗拉強度為176MPa,伸長率為6.7%;管材抗拉強度隨著固溶時間的增加先升高后下降,固溶時間為18h時達到最好,抗拉強度為181MPa,伸長率隨固溶時間的增長而升高,固溶時間為24h時達到最好,伸長率為9.2%,隨著固溶時間的增加,β-Mg17Al12相溶于基體能力增強。(4)對離心鑄造AZ91鎂合金管材進行展平,包套軋制。通過不同軋制溫度下板材對比可知:軋制溫度為400℃時,板材外形無明顯表面裂紋及邊部開裂,厚度均勻,抗拉強度及伸長率較鑄態(tài)得到明顯提高,板材伸長率及抗拉強度分別為7.2%和291MPa,軋制后板材組織均明顯細化,軋制過程中發(fā)生動態(tài)再結(jié)晶;通過不同軋制總壓下量板材對比發(fā)現(xiàn):大壓下量板材力學性能得到明顯提高,其抗拉強度及伸長率分別為317MPa和7.4%;對軋制態(tài)板材進行不同保溫時間的退火處理發(fā)現(xiàn):退火后板材塑性提高,保溫時間90min時達到最好,伸長率分別為8.6%。
[Abstract]:As the lightest metal structure material, magnesium alloy is widely used in automotive, aerospace and 3C fields, while magnesium alloy products are mainly used in the form of sheet metal. Therefore, the research and development of magnesium alloy sheet with short process, wide width and high performance has received extensive attention. Through centrifugal casting numerical simulation and casting, solid solution treatment, plate rolling and sheet annealing treatment, a set of reasonable forming process of AZ91 magnesium alloy sheet was determined. The research process is as follows: (1) the flow field and temperature field of AZ91 magnesium alloy pipes with a length of 1500 mm, an outer diameter of 400 mm and a thickness of 20mm are simulated by computer, and the results show that: in the process of centrifugal casting, When the pouring time reaches 8.4 s, the first layer of alloy liquid fills the mold for the first time, and the pouring process ends at 20 s. During the pouring process, the temperature of the alloy liquid was the highest in the gate part, and gradually decreased away from the gate. At the end of pouring, the two ends of the pipe were completely solidified, and the central part of the pipe was not solidified. (2) the length of the tube was 1500mm by centrifugal casting. The outer diameter is 400mm and the thickness of AZ91 magnesium alloy pipe is 20mm. The technological parameters of centrifugal casting are determined as follows: centrifugal rotational speed 900rr / min, pouring temperature 700 鈩，

本文編號：2321129