Sn和超声处理对Mg-6Zn-0.5Y合金组织及性能的影响

发布时间：2018-06-20 03:19

  本文选题：Mg-6Zn-0.5Y合金 + Sn　； 参考：《重庆大学》2015年硕士论文

【摘要】：本文分别采用合金化和熔体超声处理两种手段来改善合金的组织和性能,特别是合金的塑韧性,以期扩大其应用范围。实验通过采用光学显微镜、扫描电子显微镜、X射线衍射仪、电子万能试验机等进行分析表征,确定了合金最佳的成分比及最佳的超声处理功率,并系统探讨了Sn合金化和熔体超声处理对合金组织及力学性能的影响机理。Sn的添加明显细化了合金的铸态组织,且随着Sn的增加α-Mg基体逐渐向近等轴晶转变,但是当Sn含量达到4%时,晶粒有长大的趋势。Sn在合金中主要以Mg Sn Y和Mg2Sn相的形式存在。另外,铸态合金的抗拉强度和延伸率随Sn含量的增加呈先上升后下降的规律。Sn含量为1%时,合金的延伸率达到最大值,由7.2%增加到13.5%,增幅达87.5%。Sn含量为2%时,合金的抗拉强度达到最大值,由110MPa增加到189MPa,增幅达71.8%。分析认为,Sn主要通过细晶强化、固溶强化及弥散强化来提高铸态合金的性能。Mg-6Zn-0.5Y-x Sn合金经420℃/12h均匀化热处理后,Zn在晶界的偏聚基本消除,Sn在晶界的偏聚没有得到明显改善,Y的分布仍然比较均匀。其中,Mg-6Zn-0.5Y-2Sn合金的均匀化效果最为理想,随着Sn含量的继续增加,合金均匀化效果越来越差,未溶的块状化合物越来越多,分析表明这些未溶的块状化合物主要是Mg Sn Y和Mg2Sn相。Mg-6Zn-0.5Y-x Sn合金在热挤压变形过程发生了动态再结晶,晶粒得到了明显细化,随着Sn含量的增加,没有被破碎的大块状第二相逐渐增多。另外,挤压态Mg-6Zn-0.5Y-x Sn合金的抗拉强度、屈服强度、延伸率都随着Sn含量的增加呈先上升后下降的规律。当合金中Sn含量为1%时,屈服强度略有提高,抗拉强度提高则较为明显,此时延伸率达到最大值为14.8%,增幅为6.5%。当Sn含量为2%时,抗拉强度和屈服强度均达到最大值,分别为312MPa和212 MPa,增幅分别为18.6%和26.9%。继续增加Sn的含量,合金性能开始恶化。分析认为,挤压变形过程中未被破碎的大块状第二相是导致合金性能恶化的主要因素。超声处理能够显著细化Mg-6Zn-0.5Y合金的凝固组织,其细化程度与超声处理功率有关,当处理功率为600W时,晶粒细化效果最好。另外,未经超声处理铸态Mg-6Zn-0.5Y合金的准晶I相在晶界呈粗大的半连续网状分布,经超声处理后,准晶I相在晶界明显细化、弥散化,且随着处理功率的提高,准晶I相的面积分数逐渐减少。最后随着超声处理功率的提高,铸态Mg-6Zn-0.5Y合金的抗拉强度和延伸率呈先上升后下降的趋势,当处理功率为600W时,两者均达到最大值分别为184MPa和11.2%,比未处理时分别提高了67.3%和55.6%。分析认为,弥散分布的准晶I相是促进铸态Mg-6Zn-0.5Y合金力学性能提高的主要因素。
[Abstract]:In this paper, alloying and melt ultrasonic treatment are used to improve the microstructure and properties of the alloy, especially the ductility of the alloy, in order to expand its application range. By means of optical microscope, scanning electron microscope, X-ray diffractometer and electronic universal testing machine, the optimum composition ratio and ultrasonic treatment power of the alloy were determined. The effects of Sn alloying and melt ultrasonic treatment on the microstructure and mechanical properties of the alloy were systematically discussed. The as-cast microstructure of the alloy was obviously refined with the addition of Sn, and the 伪 -Mg matrix gradually changed to the near equiaxed crystal with the increase of Sn. However, when Sn content reaches 4, the grain size tends to grow in the form of mg Sn Y and mg 2Sn phase. In addition, with the increase of Sn content, the tensile strength and elongation of the as-cast alloy increased first and then decreased. When the content of Sn was 1, the elongation of the alloy reached the maximum value, from 7.2% to 13.5%, with an increase of 87.5. The tensile strength of the alloy reached its maximum value, from 110 MPA to 189 MPA, with an increase of 71.8%. It is considered that Sn is mainly strengthened by fine grain. Solid solution strengthening and dispersion strengthening to improve the properties of as-cast alloys. After 420 鈩，

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