■ 제 목:  중엔트로피 합금의 심한 격자 뒤틀림


 연 사:  손석수 교수 (고려대학교)  


■  일 시:  5월 28일(화) 16:00


■ 장 소:  응용공학동 (W1) 1층 영상강의실


 Host :  강기범 교수 


 Abstract :   


Severe lattice distortion is a core effect in the design of multi-principal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium- and high-entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of lattice distortion. Here, based on a combined theoretical and experimental approach, I’ll introduce that the degree of lattice distortion is indeed a key parameter in controlling strengthening mechanisms for the design of hitherto unexplored ultrastrong medium-entropy single-phase alloys. Vanadium (V) is exploited as a very efficient element in a disordered VCoNi solid solution alloy. It is demonstrated that a wide fluctuation of the atomic bond distances in such alloys, i.e., severe lattice distortion, improves both yield stress and its sensitivity to grain size. Due to this enhanced Hall-Petch dependency, the VCoNi alloy could present 1.3 GPa of yield strength at 1mm of average grain size. In addition, the dislocation-mediated plasticity effectively enhances the strength–ductility relationship by generating nanosized dislocation substructures due to massive pinning.