本文選題：AZ31鎂合金　切入點：La　出處：《合肥工業(yè)大學》2017年碩士論文

【摘要】：鎂合金作為最輕的輕質金屬結構材料,商業(yè)應用前景相當廣闊,被譽為“21世紀綠色結構材料”。然而對于密排六方晶體結構的鎂合金,由于其室溫塑性差,成型困難和絕對強度低等問題,嚴重制約鎂合金的發(fā)展。本文采用室溫拉伸、維氏硬度及電化學腐蝕測試方法,金相(optical microstructure,OM),X射線衍射(X-ray,XRD)、能譜掃描(energy spectrum analysis,EDS)、電子顯微鏡(SEM)等分析手段,研究了稀土La改性、冷軋工藝和再結晶退火工藝等因素對AZ31鎂合金的微觀組織結構、力學性能以及耐蝕性能的影響規(guī)律。取得的主要研究結論和成果如下(1)設計了5組合金成分,La的加入量分別為0.2%、0.3%、0.4%、0.6%和0.9%。研究表明:添加微量La,能夠細化AZ31鑄態(tài)組織,獲得具有細小等軸形貌的晶粒;同時細化了原始粗大的第二相Mg17Al12,產生熱穩(wěn)定性良好、細小針狀的析出相Al11La3。當La的含量為0.6%時,合金鑄態(tài)組織晶粒大小約為40μm,晶粒最細小,合金力學性能最優(yōu)。另外,添加La能提高合金的抗腐蝕性能,當La含量為0.4%時合金耐腐蝕性能較優(yōu),此時時效態(tài)變形合金(總加工率約為75%)的靜態(tài)腐蝕深度為10mm/a,且隨著La的繼續(xù)增加,抗腐蝕性能降低,當La含量為0.6%時,其靜態(tài)腐蝕深度為17.9mm/a,仍優(yōu)于商用AZ31鎂合金(靜態(tài)腐蝕深度約為60mm/a)。(2)設計了3組冷軋工藝,變形量分別為10%、20%和30%,以探究冷軋工藝參數(shù)對AZ31-0.6La合金組織與性能的影響規(guī)律。研究表明:合金臨界冷軋壓下量為30%,超過30%,合金組織將會碎裂。當合金的冷軋量為10%時,冷軋過后合金內部產生了大量位錯和孿晶,經過240℃×1h+200℃×24h熱處理后,合金能獲得較優(yōu)的力學性能和抗腐蝕性能,其時效態(tài)(合金總加工率約為75%)抗拉強度與屈服強度、延伸率和靜態(tài)腐蝕深度分別為:340MPa/240MPa、25%、1.02mm/a。(3)通過設計再結晶退火工藝的溫度(240℃、280℃和320℃)和時間(t=5、10…180min),研究再結晶退火工藝對AZ31-0.6La合金經10%冷軋后的組織與性能的影響規(guī)律。研究表明:合金板材經240℃×2.5h退火處理后,發(fā)生完全再結晶,獲得晶粒最細小且均勻的合金組織。(4)結合顯微硬度測試(AZ31-0.6La冷軋量5%、10%和15%,240℃、280℃和320℃,t=5、10…180min)和Arrhenius方程,確定了AZ31鎂合金發(fā)生靜態(tài)再結晶的激活能,建立了AZ31鎂合金的靜態(tài)再結晶動力學方程和晶粒尺寸模型。
[Abstract]:As the lightest light metal structure material, magnesium alloy has a broad prospect of commercial application and is praised as "green structural material in the 21st century".However, the development of magnesium alloys with dense hexagonal crystal structure is seriously restricted because of its poor room temperature plasticity, difficult forming and low absolute strength.In this paper, rare earth La modification was studied by means of room temperature stretching, Vickers hardness and electrochemical corrosion test, X-ray diffraction X ray diffraction (X ray diffraction), energy spectrum analysis (EDS), electron microscopy (SEM), etc.Effects of cold rolling and recrystallization annealing on microstructure, mechanical properties and corrosion resistance of AZ31 magnesium alloy.The main conclusions and results obtained are as follows: 1) the addition amount of La in 5 combinations is 0.20.30.30.40% and 0.9% respectively.The results show that the as-cast microstructure of AZ31 can be refined by adding a small amount of La, and the grains with fine equiaxed morphology can be obtained, and the coarse second phase Mg17Al12 is refined, resulting in good thermal stability and fine needle-like precipitated phase Al11La3.When the content of La is 0.6, the grain size of the as-cast alloy is about 40 渭 m, the grain size is the smallest, and the mechanical properties of the alloy are the best.In addition, the addition of La can improve the corrosion resistance of the alloy. When La content is 0.4, the corrosion resistance of the alloy is better, and the static corrosion depth of the aging deformed alloy (total processing rate is about 75mm / a) is 10 mm / a, and increases with the increase of La content.When La content is 0.6, its static corrosion depth is 17.9 mm / a, which is still superior to commercial AZ31 magnesium alloy (the static corrosion depth is about 60 mm / a) and three groups of cold rolling process have been designed.The deformation amounts are 10% and 30% respectively to investigate the effect of cold rolling process parameters on the microstructure and properties of AZ31-0.6La alloy.The results show that the critical cold rolling reduction of the alloy is 30 and above 30, the microstructure of the alloy will break.When the cold rolling amount of the alloy is 10, a large number of dislocations and twins occur inside the alloy after cold rolling. After heat treatment at 240 鈩，

本文編號：1714460