| The structure, mechanical property and thermal stability of rapidly solidified aluminum-transition metal (=Fe, Co, Zr) alloy system were investigated. The structure was changed from Al phase to amorphous one through a mixed structure consisted of Al and amorphous phases with solute content. The amorphous single phase was formed at the Al-rich compositional range of Al=87-88at%. The crystallization temperature(T_x,) of amorphous Al_(88)Ni_(12-x)(Fe,Co)_x(X≤6at%) alloys was increased with the content of Fe or Co, indicating the thermal stabilization of the amorphous phase. Hardness (H_v,) and tensile fracture strength (σ_f) exhibited a maximum at the 5at% Fe or Co. On the other hand, aging treatment at temperature range less than 500K in amorphous Al_(88)Ni_9(Co,Fe)₃ alloys formed aluminum nanoparticles distributed homogeneously in an amorphous matrix. The H_v for the mixed phase alloy increased monotonically with the V_f. The σ_f showed a maximum at about 15%V_f and with further increase of the V_f decreased due to the embrittleness of the amorphous matrix. The increase is presumed because the Al particles act as an effective barrier to shear deformation of the amorphous matrix. The ultimate tensile fracture strength at elevated temperature less than 480K in an amorphous Al_(88)Ni_8Zr₃ alloy kept a high level more than 650㎫ and exhibited a large elongation of 25% at 440K. The large elongation can be explained by crystallization-induced plasticity. |
|
