含长周期结构Mg-Y-Zn合金组织形态控制及性能研究
发布时间：2018-09-04 15:59
【摘要】：镁合金具有密度小、优异的电磁屏蔽及极佳的阻尼减震等性能吸引研究学者,在航空、电子及体育器材等领域具有广泛应用前景。未经过处理的铸态Mg_(97)Zn_1Y_2合金中组织形貌对其耐磨性、耐腐蚀性、强度等性能的影响。因此,本文采用变质处理、机械搅拌、等温热处理及亚快速凝固方法对含长周期结构Mg_(97)Zn_1Y_2合金的组织及性能进行研究。主要研究结论如下:(1)Mg_(97)Zn_1Y_2加入少量Si元素后,Mg_(97)Zn_1Y_2合金组织中出现了颗粒物相,长周期从条状变为孤岛态;加入1.8wt.%Si的合金中出现粗大的汉字状Mg2Si相,此时合金的硬度达到95.5HV,提高了40%。加入0.2wt.%Si的Mg_(97)Zn_1Y_2合金抗拉强度和伸长率明显高于铸态Mg_(97)Zn_1Y_2合金,其抗拉强度达到220Mpa,伸长率为10%,分别增加24%和36%。细小的Mg5Si6或Mg2Si颗粒相均匀地分布于镁基体中,能有效阻碍腐蚀液中Cl-的渗入,大大降低合金腐蚀速率。(2)对Mg_(97)Zn_1Y_2合金施加机械搅拌后,其内部长周期相变为孤岛状,从冰花状枝晶开始破碎,破碎枝晶组织变得细小相连,熟化后变成玫瑰蔷薇状。当搅拌时间5min,合金硬度值增长32%,其伸长率达最大为11%,抗拉强度为191MPa,伸长率增值较大为50%;随着搅拌时间延长,镁合金的组织细化和成分分布均匀,合金腐蚀下降。合金通过高速剪切速率搅拌易较快达到蔷薇状;当搅拌速度达到700r/min,此时硬度值增至110HV,增幅61%,抗拉强度达到210MPa,伸长率为8.3%,抗拉强度及伸长率增幅分别为18.6%和13.7%。随着剪切速率的增加,熟化的蔷薇状有利于改善镁合金的腐蚀能力,但同时合金经搅拌后的晶界处组织粗大,由于腐蚀主要发生在晶界处,晶界易受腐蚀后且易显露出来,加速镁合金腐蚀速率。(3)在等温热处理时,合金保温温度从540℃~600℃,组织尺寸由大-小-大的顺序变化,经过了分离及球化至最后粗化三个过程。等温温度为575℃下合金的组织演变趋势大致为:枝晶态-不规则球形和块状-球形状,当保温时间15min,其组织为均匀、圆整的球状晶。(4)吸铸合金组织由三个区域组成,分别为:外围细小等轴晶区,中间柱状组织区,内部粗大等轴晶区。当吸铸合金直径为8mm,冷却速率约为63.8k/s,一次枝晶臂间距为25μm;直径为4mm,则其冷却速率约为138k/s,二次枝晶臂间距为9.67μm。冷却速度提高可减少其晶界偏析,有效抑制元素富集,组织趋于均匀分布。
[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，
本文编号：2222658
[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，
本文编号：2222658
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