In this study, we report the microstructure and characterization of Ta20Nb20V20W20Ti20 high-entropy alloy powders and sintered samples. The effects of milling time on the microstructure and mechanical properties were investigated in detail. Microstructure and structural characterization were performed by scanning electron microscopy and X-ray diffraction. The mechanical properties of the sintered samples were analyzed through a compressive test at room temperature with a strain rate of 1 × 10−4 s−1. The microstructure of sintered Ta20Nb20V20W20Ti20 high-entropy alloy is composed of a BCC phase and a TiO phase. A better combination of compressive strength and strain was achieved by using prealloyed Ta20Nb20V20W20Ti20 powder with low oxygen content. The results suggest that the oxide formed during the sintering process affects the mechanical properties of Ta20Nb20V20W20Ti20 high-entropy alloys, which are related to the interfacial stability between the BCC matrix and TiO phase.

니오븀 금속을 기반으로 하는 Nb56Ti23Ni21 합금 분리막의 수소 투과 특성 및 화학적 안정성에 관한 연구를 수행하였다. 이를 위하여 직경 10 mm, 두께 0.5 mm의 Nb56Ti23Ni21 합금 분리막을 제작하였으며, 2가지 조성(H2 100%, H2 60% + CO2 40%)의 공급가스를 450℃의 온도에서 투과시킬 때 압력에 따른 수소 투과 특성에 관한 실험을 진행하였다. 본 실험에서의 최대 수소 투과량은 순수한 수소를 투과시킬 경우 절대압력 3 bar에서 5.58mL/min/cm2로 나타났다. 또한 공급가스 조성에 따른 각각의 경우 모두 Sievert's law에 잘 부합하였으며, 이산화탄소와의 혼합가스 사용시, 투과량은 수소 분압 감소에 비례하여 감소하였다. 투과 실험 후 XRD 분석을 통하여 Nb56Ti23Ni21 합금 분리막의 이산화탄소에 대한 화학적 안정성에 대한 실험을 수행하였다.

Al-42wt%Nb powder was prepared by high-energy mechanical milling(HEMM). The particle size, phase transformation and microstructure of the as-milled powder were investigated by particle size distribution (PSD) analyzer, scanning electron microscopy (SEM), X-ray diffractometery (XRD), transmission electron microscopy (TEM)and differential thermal analysis (DTA). The milled powders were heated to a sintering temperature at 1000C with under vaccum with vaccum tube furnace. Microstructural examination of sintered Ti-42wt%Nb alloy using 4h-milled powder showed Ti-rich phases (α-Ti) which are fine and homogeneously distributed in the matrix (Nb-rich phase: β-Ti). The sintered Ti-42wt%Nb alloy with milled powder showed higher hardness. The microstructure of the as quenched specimens fabricated by sintering using mixed and milled powder almost are same, but the hardness of as quenched specimen fabricated by using mixed powder increased due to solution hardening of Nb in Ti matrix. The aging effect of these specimens on microstructural change and hardening is not prominent.