Al-Mm-Ni 계 비정질합금의 미세조직과 기계적 특성 = Microstructure and Mechanical Properties of Al-Mm-Ni Amorphous Alloys

다국어 초록 (Multilingual Abstract)

The objectives of this study are firstly to find optimum fabrication condition of the high strength Al-Mm(misch metal)-Ni and Al-Mm-Ni-Fe amorphous alloys made by a single roll melt-spinner in air and vacuum, and secondly to investigate the correlation of the mechanical properties and microstructure of the alloys. Alloys containing about 4 at.% Mm and 10 at.% Ni content revealed uniform amorphous phase, and showed high fracture strength. Among these alloys Al_(86)-Mm₄-Ni_8-Fe₂ alloy, melt-spun in vacuum, showed the highest fracture strength of about 850MPa. Meltspun Al_(86)-Mm₄-Ni_(10) amorphous alloy showed two-stage crystallization from amorphous to amorphous matrix phase with fcc-Al particles, and then to amorphous matrix phase containing intermetallic compounds. As annealing temperature increased, fracture strength and elongation decreased in the range up to about 350℃, and then increased again. The decrease in fracture strength seems to be caused by a decrease of free volume of amorphous phase by the structural relaxation before the formation of fcc-Al particles, in conjunction with an enhancement of embrittlement after formation of fcc-Al particles. The replacement of Ni content by 2 at.% of Fe in Al_(86)-Mm₄-Ni_(10) alloy resulted in an increase of both thermal stability and the mechanical properties. This can be explained in terms of increased attractive bonding force among the constituent atoms by the replacement of Fe.