本文選題：Mg-6Zn-0.5Y合金 + Sn�。� 參考：《重慶大學》2015年碩士論文

【摘要】：本文分別采用合金化和熔體超聲處理兩種手段來改善合金的組織和性能,特別是合金的塑韌性,以期擴大其應用范圍。實驗通過采用光學顯微鏡、掃描電子顯微鏡、X射線衍射儀、電子萬能試驗機等進行分析表征,確定了合金最佳的成分比及最佳的超聲處理功率,并系統(tǒng)探討了Sn合金化和熔體超聲處理對合金組織及力學性能的影響機理。Sn的添加明顯細化了合金的鑄態(tài)組織,且隨著Sn的增加α-Mg基體逐漸向近等軸晶轉(zhuǎn)變,但是當Sn含量達到4%時,晶粒有長大的趨勢。Sn在合金中主要以Mg Sn Y和Mg2Sn相的形式存在。另外,鑄態(tài)合金的抗拉強度和延伸率隨Sn含量的增加呈先上升后下降的規(guī)律。Sn含量為1%時,合金的延伸率達到最大值,由7.2%增加到13.5%,增幅達87.5%。Sn含量為2%時,合金的抗拉強度達到最大值,由110MPa增加到189MPa,增幅達71.8%。分析認為,Sn主要通過細晶強化、固溶強化及彌散強化來提高鑄態(tài)合金的性能。Mg-6Zn-0.5Y-x Sn合金經(jīng)420℃/12h均勻化熱處理后,Zn在晶界的偏聚基本消除,Sn在晶界的偏聚沒有得到明顯改善,Y的分布仍然比較均勻。其中,Mg-6Zn-0.5Y-2Sn合金的均勻化效果最為理想,隨著Sn含量的繼續(xù)增加,合金均勻化效果越來越差,未溶的塊狀化合物越來越多,分析表明這些未溶的塊狀化合物主要是Mg Sn Y和Mg2Sn相。Mg-6Zn-0.5Y-x Sn合金在熱擠壓變形過程發(fā)生了動態(tài)再結(jié)晶,晶粒得到了明顯細化,隨著Sn含量的增加,沒有被破碎的大塊狀第二相逐漸增多。另外,擠壓態(tài)Mg-6Zn-0.5Y-x Sn合金的抗拉強度、屈服強度、延伸率都隨著Sn含量的增加呈先上升后下降的規(guī)律。當合金中Sn含量為1%時,屈服強度略有提高,抗拉強度提高則較為明顯,此時延伸率達到最大值為14.8%,增幅為6.5%。當Sn含量為2%時,抗拉強度和屈服強度均達到最大值,分別為312MPa和212 MPa,增幅分別為18.6%和26.9%。繼續(xù)增加Sn的含量,合金性能開始惡化。分析認為,擠壓變形過程中未被破碎的大塊狀第二相是導致合金性能惡化的主要因素。超聲處理能夠顯著細化Mg-6Zn-0.5Y合金的凝固組織,其細化程度與超聲處理功率有關(guān),當處理功率為600W時,晶粒細化效果最好。另外,未經(jīng)超聲處理鑄態(tài)Mg-6Zn-0.5Y合金的準晶I相在晶界呈粗大的半連續(xù)網(wǎng)狀分布,經(jīng)超聲處理后,準晶I相在晶界明顯細化、彌散化,且隨著處理功率的提高,準晶I相的面積分數(shù)逐漸減少。最后隨著超聲處理功率的提高,鑄態(tài)Mg-6Zn-0.5Y合金的抗拉強度和延伸率呈先上升后下降的趨勢,當處理功率為600W時,兩者均達到最大值分別為184MPa和11.2%,比未處理時分別提高了67.3%和55.6%。分析認為,彌散分布的準晶I相是促進鑄態(tài)Mg-6Zn-0.5Y合金力學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 偽 -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，

本文編號：2042699