Crystallization process in rapidly solidified Al-Nd-Ni amorphous alloy prepa red by melt spinning

1　INTRODUCTIONIntherecentfew years ,Al richmetallicglasshasbeenpaidmoreandmoreattentiontointhenovelmaterialsresearchfield ,notonlyduetoitshighstrength ,hardnessandlowdensity ,butalsobecauseanew typeAl basednanophasecompositecanbeob tainedfromitbypartialcrystallization[17] .ManyAl basedamorphous/nanocrystallinealloyscontainingrareearth(RE =La ,Y ,Ce ,Nd ,etc)andtransitionmetal(TM =Fe ,Co ,Ni,etc)elementshaveanattractivecombinationofmechanicalproper ties .Ithasbeenreportedthatmanyofth…

Crystallization process in rapidly solidified Al-Nd-Ni amorphous alloy prepared by melt spinning

Rapidly solidified ribbons of Al90 Nd7 Ni3 metallic glasses were prepared by using melt spinning. Crystal lization process of the totally amorphous ribbons was investigated by differential scanning calorimetry and X-ray diffraction analysis, under continuous heating regime. The results show that, under continuous heating regime, the metallic glass devitrifies via two main stages: primary crystallization, resulting in two-phase mixture of α(Al) plus residual amorphous phase, and secondary crystallization, corresponding to some inter-metallic phases appearing,successively including Al11 Nd3, Al3 Ni, and some unknown phases, in the Al amorphous/crystal matrix. Four peaks appear on the continuous heating DSC curves. Their peak temperatures are respectively 470.8, 570.8, 585.6, and731.6 K at infinitesimal heating rate, and their activation energies of the respective phase transformation are 183.0,294.7, 232.5 and 269.1 kJ/mol. The values of Avrami exponent of the four reactions decrease with increasing relative transformation degree. At the earlier stage of phase transformation, the values of n are larger than 4, and at the later stage the values of n become close to some value from 0.5 to 2.0.