【摘要】：鎂合金具有密度小、優(yōu)異的電磁屏蔽及極佳的阻尼減震等性能吸引研究學者,在航空、電子及體育器材等領域具有廣泛應用前景。未經過處理的鑄態(tài)Mg_(97)Zn_1Y_2合金中組織形貌對其耐磨性、耐腐蝕性、強度等性能的影響。因此,本文采用變質處理、機械攪拌、等溫熱處理及亞快速凝固方法對含長周期結構Mg_(97)Zn_1Y_2合金的組織及性能進行研究。主要研究結論如下:(1)Mg_(97)Zn_1Y_2加入少量Si元素后,Mg_(97)Zn_1Y_2合金組織中出現(xiàn)了顆粒物相,長周期從條狀變?yōu)楣聧u態(tài);加入1.8wt.%Si的合金中出現(xiàn)粗大的漢字狀Mg2Si相,此時合金的硬度達到95.5HV,提高了40%。加入0.2wt.%Si的Mg_(97)Zn_1Y_2合金抗拉強度和伸長率明顯高于鑄態(tài)Mg_(97)Zn_1Y_2合金,其抗拉強度達到220Mpa,伸長率為10%,分別增加24%和36%。細小的Mg5Si6或Mg2Si顆粒相均勻地分布于鎂基體中,能有效阻礙腐蝕液中Cl-的滲入,大大降低合金腐蝕速率。(2)對Mg_(97)Zn_1Y_2合金施加機械攪拌后,其內部長周期相變?yōu)楣聧u狀,從冰花狀枝晶開始破碎,破碎枝晶組織變得細小相連,熟化后變成玫瑰薔薇狀。當攪拌時間5min,合金硬度值增長32%,其伸長率達最大為11%,抗拉強度為191MPa,伸長率增值較大為50%;隨著攪拌時間延長,鎂合金的組織細化和成分分布均勻,合金腐蝕下降。合金通過高速剪切速率攪拌易較快達到薔薇狀;當攪拌速度達到700r/min,此時硬度值增至110HV,增幅61%,抗拉強度達到210MPa,伸長率為8.3%,抗拉強度及伸長率增幅分別為18.6%和13.7%。隨著剪切速率的增加,熟化的薔薇狀有利于改善鎂合金的腐蝕能力,但同時合金經攪拌后的晶界處組織粗大,由于腐蝕主要發(fā)生在晶界處,晶界易受腐蝕后且易顯露出來,加速鎂合金腐蝕速率。(3)在等溫熱處理時,合金保溫溫度從540℃~600℃,組織尺寸由大-小-大的順序變化,經過了分離及球化至最后粗化三個過程。等溫溫度為575℃下合金的組織演變趨勢大致為:枝晶態(tài)-不規(guī)則球形和塊狀-球形狀,當保溫時間15min,其組織為均勻、圓整的球狀晶。(4)吸鑄合金組織由三個區(qū)域組成,分別為:外圍細小等軸晶區(qū),中間柱狀組織區(qū),內部粗大等軸晶區(qū)。當吸鑄合金直徑為8mm,冷卻速率約為63.8k/s,一次枝晶臂間距為25μm;直徑為4mm,則其冷卻速率約為138k/s,二次枝晶臂間距為9.67μm。冷卻速度提高可減少其晶界偏析,有效抑制元素富集,組織趨于均勻分布。
[Abstract]:Magnesium alloys with low density, excellent electromagnetic shielding and excellent damping and shock absorption properties attract researchers, and have a wide application prospect in aviation, electronics and sports equipment. Effect of microstructure morphology on wear resistance, corrosion resistance and strength of as-cast Mg_ _ (97) Zn_1Y_2 alloy without treatment. Therefore, the microstructure and properties of Mg_ _ (97) Zn_1Y_2 alloy with long-period structure were studied by means of modification, mechanical stirring, isothermal heat treatment and subrapid solidification. The main conclusions are as follows: (1) the granular phase appeared in the microstructure of Mg_ _ (97) Zn_1Y_2 alloy after adding a small amount of Si element, the long period changed from strip to island state, and the coarse Chinese character Mg2Si phase appeared in the alloy with 1.8wt.%Si, and the hardness of the alloy reached 95.5 HVV, which increased the hardness of the alloy by 40 steps. The tensile strength and elongation of Mg_ (97) Zn_1Y_2 alloy added with 0.2wt.%Si were significantly higher than that of as cast Mg_ (97) Zn_1Y_2 alloy. The tensile strength and elongation of Mg_ (97) Zn_1Y_2 alloy were 220 MPA and 10, respectively, which increased by 24% and 36%, respectively. The fine Mg5Si6 or Mg2Si particles are uniformly distributed in magnesium matrix, which can effectively block the infiltration of Cl- in the corrosion solution and greatly reduce the corrosion rate of the alloy. (2) after mechanical stirring of Mg_ (97) Zn_1Y_2 alloy, the internal long period phase becomes isolated island. The broken dendritic structure becomes fine and connected from ice flower dendrite to rose after ripening. When the stirring time is 5 min, the hardness value of the alloy increases 32%, the elongation reaches the maximum of 11 MPA, the tensile strength is 191 MPA, and the elongation increment is 50%. With the prolongation of the stirring time, the microstructure of the magnesium alloy is refined and the composition is evenly distributed, and the corrosion of the alloy decreases. When the stirring speed is 700 rmin, the hardness increases to 110 HVV, the tensile strength is 210 MPA, the elongation is 8.3%, and the tensile strength and elongation increase by 18.6% and 13.7%, respectively. With the increase of shear rate, the aging rose shape is beneficial to improve the corrosion ability of magnesium alloy, but at the same time, the grain boundary of the alloy after stirring is coarse, because the corrosion occurs mainly at the grain boundary, the grain boundary is easy to be corroded and exposed. (3) during isothermal heat treatment, the alloy holding temperature changed from 540 鈩，

本文編號：2222658