超輕鎂鋰合金的拉伸與疲勞特性研究; Tensile and Fatigue Properties Study of Superlight Mg-Li Alloys

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Title:	超輕鎂鋰合金的拉伸與疲勞特性研究;Tensile and Fatigue Properties Study of Superlight Mg-Li Alloys
Authors:	鍾仕豪;Ser-how Chong
Contributors:	機械工程研究所
Keywords:	鎂鋰合金;固溶強化;抗拉強度;疲勞限;Mg-Li Alloys;Solid Solution Hardening;Ultimate Strength;Fatigue Limit
Date:	2011-07-04
Issue Date:	2012-01-05 12:28:06 (UTC+8)
Abstract:	本研究目的為探討新型超輕鎂鋰合金之拉伸與疲勞特性。選用具有低密度及室溫良好成型性之Mg-Li系列合金為研究對象，分別為LAZ1110和添加Be、Sc元素之LAZ1110+Be+Sc兩種合金。但由於此系列合金缺乏足夠的機械強度，故利用固溶處理來強化來提昇其機械強度。　　顯微組織方面，兩種合金皆呈現α+β的雙相組織結構，並在晶粒內部有“費德曼組織”的出現；添加了Be、Sc元素的鎂鋰合金，其晶粒大小則略低於原材。經350℃/1小時固溶處理後，兩種材料均呈現單一β相組織，並且晶粒明顯粗大化。　　機械性質方面，LAZ1110的抗拉強度為 150MPa，添加Be、Sc元素後由於細晶強化的效果，強度略為提昇至157MPa。固溶後兩種材料的抗拉強度皆提昇了將近100MPa，強化效果顯著。LAZ1110和LAZ1110+Be+Sc的應變硬化程度相差不大，然而固溶強化後卻有明顯的提昇，增加了材料抑制頸縮變形的能力。　　LAZ1110、LAZ1110+Be+Sc的疲勞限分別為35MPa和43MPa，並有觀察到α相顆粒有延緩裂縫成長的效果。固溶強化後由於材料內部差排移動受阻的影響，使得兩種材料的疲勞限明顯增加。 This research focuses on the tensile and fatigue properties of super-light Mg-Li Alloy. LAZ1110 with low-density and good room temperature forming was chosen as the subject, and Be, Sc were added to form LAZ1110+Be+Sc. However, this kind of alloy lacked strength, so it was strengthened by using solid solution hardening. As for the microscopic, both alloys present the two-phased structure of α+β, and “Widmansta ̈tten Structure” also appeared. The addition of Be, Sc reduced the grain size of Mg-Li alloys. After solid solution hardening, both alloys present single β phase, whose grain size coarsening apparently. The ultimate strength of LAZ1110 is 150MPa, and after Be, Sc addition its strength increased to 157MPa due to effect of fine grain size strengthening. After solid solution hardening, both alloys’ ultimate strength increased by nearly 100MPa. The ability of strain hardening of LAZ1110 is close to that of LAZ1110+Be+Sc, but the each ability of strain hardening increases apparently after heat-solute treatment. The fatigue limit of LAZ1110 is 35MPa, and that of LAZ1110+Be+Sc is 43MPa, but α phase was observed to delay the crack propagation. After solid solution hardening, due to dislocation strain field interaction, the fatigue limit of two alloys apparently increased.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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