高熵合金有別於傳統合金擁有獨特的顯微結構以及優越的機械性質，在應用中引起極大的研究關注。過去十幾年，大部分的研究主要專注於多元等量的成分合金上。而本研究將探討非等量高熵合金之成分設計，欲設計出密度在5 g/cm3且具有高強度(降伏強度1200MPa)以及高延展性(塑性變形15%)的高熵合金。 本研究選取Ti(AlCrNbV)系列合金添加微量原子半徑較小且有高彈性模數的鎳，達到固溶強化的效果；經過成分的微調找出具有較佳延性的成分比例Ti(AlCrNbV)Ni1、Ti(AlCrNbV)Ni3，再利用不同的熱機處理製程(一)冷軋70 %、(二)冷軋85 %以及(三)熱軋50 %後再冷軋70 %等三種加工硬化方式，和四個不同再結晶溫度為809℃、853℃、882℃、926℃後馬上進行水淬。 由拉伸試驗結果得知，隨著再結晶溫度提高，降伏強度下降，延性增加，而Ti(AlCrNbV)Ni3經過冷軋85%和熱軋50%後再冷軋70%這兩種加工方式再進行853℃的再結晶熱處理，其降伏強度分別為1250 MPa和1232 MPa且延性都16%以上，符合本實驗期望降伏強度提高至1200MPa且塑性變形15%以上。 ;High-entropy alloys (HEA) attract great attention in past few decades. Most HEA researches mainly concentrate on the heavier multi-principal elements with equiatomic or near-equiatomic alloys. In this study, we focus on the light-weight and non-equiatomic medium-entropy alloys (MEA) system with low density (5 g/cm3) and high strength (yield strength of 1200 MPa) and high ductility (plastic deformation of 15%). In this study, the Ti(AlCrNbV) series alloy was selected to add a small amound nickel with smaller atomic radius and high elastic modulus form the Ti(AlCrNbV)Ni series alloy, which was added in a small amount to achieve the effect of solid solution strengthening and maintain the single-phase BCC structure. The optimal composition is Ti(AlCrNbV)Ni1 and Ti(AlCrNbV)Ni3 alloys, Moreover, there two alloys were thermomechanical treated by different processes: (1) Cold rolled 70% (2) Cold rolled 85% (3) Hot rolled 50% then cold rolled 70%. Three different work hardening processes and then follow by annealing temperature ,809°C, 853°C, 882°C, and 926°C, and then immediately water quenched. According to the results of the tensile test, as increasing the recrystallization temperature the yield strength decreases and the ductility increases. Both of the specimen of cold-rolled 85% and hot-rolled 50% then cold-rolled 75% exhibit Yield strength of 1250 MPa and 1232 MPa, respectively after recrystallized at 853℃.Meanwhile, both specimen present similar tensile ductility of 16%.
