五元富鋁低密度高熵合金之微結構觀察與其機械性質研究;Microstructure and mechanical properties of low density Al-rich quinary high entropy alloys

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Title:	五元富鋁低密度高熵合金之微結構觀察與其機械性質研究;Microstructure and mechanical properties of low density Al-rich quinary high entropy alloys
Authors:	林彥廷;Lin, Yen-Ting
Contributors:	機械工程學系
Keywords:	高熵合金;低密度;high-entropy alloys;low density
Date:	2020-08-13
Issue Date:	2020-09-02 19:12:44 (UTC+8)
Publisher:	國立中央大學
Abstract:	高熵合金具有卓越的機械性質，但大都密度偏高，這在能耗的觀點上是較不利的，而如果能設計出一個低密度的高熵合金，又同時擁有良好的機械性質，便有機會能夠取代市面上的鋁合金及鈦合金。為了能夠達到設計需求，採用五元非等量高熵合金的設計方法，以低密度的Al做為主要元素，添加Ti、Cr、Mn、V四種元素，藉由控制Al元素在50%原子比例，製作Al50TiCrMnV合金系統，成功製作出密度在5g/cm3以下的雙相低密度高熵合金。在合金設計中，藉由調整Ti、Cr、Mn、V元素的比例，探討各個元素在這五元高熵合金系統的影響。本實驗合金結構大都為FCC + BCC雙相，但在Ti元素不夠充足的情況下，會使相結構轉變，因此合金設計只要注意Ti含量足夠的情況下，即可達成雙相之五元低密度高熵合金。根據測試結果，增加Ti元素會使材料軟化；而Mn元素並不扮演著會大幅影響強度的角色；另外，Cr、V這兩種元素的添加量增加，都會對硬度及強度有明顯的增幅，因此可藉由些許元素的改變，以得到期望之機械性質。其中在Al50TiCrMn高熵合金系統裡，機械性質最好的成分為Al50Ti20Cr10Mn15V5，其降伏強度為705MPa，最大抗壓強度到達1820MPa，壓縮率則是36%。根據微結構的觀察，發覺相的形貌與機械性質會有關聯，相形貌如果呈現細針狀和竹葉狀這種細長樣並且整體排序整齊，都可預期會有不錯的機械性質。 ;Most high-entropy alloys (HEAs) possess excellent mechanical properties but high density. The resulting properties are not suitable in energy and transportation areas. In this work, a novel series light-weight (≦ 5 g/cm3) HEA with good mechanical properties will be developed which can replace the commercial aluminum alloys and titanium alloys in the near future. To meet the requirement of light-weight, light elements were chosen to design the alloys accompanied with non-equiatomic concept. Aluminum was designated as the principal element, and other minor elements such as the titanium, chromium, manganese and vanadium were added to investigate the effect of different elements. In this study, light-weight Al50TiCrMnV series alloys were introduced. The XRD results revealed that these as-cast alloys are composed of dual-phase (BCC + FCC) structure. The structure of these as-cast alloys and the morphology of FCC phase are strongly influenced by the Ti and Mn content. Additionally, the compressive strength of these as-casted alloys are affected by the Cr and V content. The optima mechanical properties occurred at the alloy of Al50Ti20Cr10Mn15V5 with compressive yield strength of 705 MPa, ultimate compressive strength of 1820 MPa, and plastic strain of 36 %. According to the observation of SEM, the morphology of FCC phase will influence their mechanical properties. With fine FCC phases, these as-cast alloys will demonstrate excellent mechanical compressive properties and outstanding specific compressive strength which led it to be a promising materials on the application of energy industries.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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