Magnetism And Effect Of High Magnetic Field On The Crystallization Of Al-Ni-Y Amorphous Alloys

Al-based amorphous alloys possess excellent mechanical properties and corrosion resistance, and have attracted the researchers' attention in recent years. But the sample size of Al-based amorphous alloys developed at present is quite small, and the crystallization temperature is quite low (100～250℃), which limits its practical application to some extent. Adding a small amount of Ni and Y elements in Al alloys as ternary alloys, is expected to form new materials with special magnetism. After partially crystallization of Al-based amorphous alloys, nano-Al crystals precipitate within amorphous matrix, and the strength can be further improved to above 1500MPa. The performance of the nano-aluminum /amorphous phase composite has close relationship with the shape, size, distribution of the nano Al particles. The introduction of high magnetic field is expected to change the shape, size and distribution of the nano-Al crystals which precipitate after partial crystallization of Al-based amorphous alloy, so as to improve the comprehensive properties. In this thesis the alloys ribbons of Al92-xNixY8 (x= 2,3,4,5,6,7,8,12) were prepared, the magnetism of both fully amorphous and partially crystallized Al90Ni2Y8 and Al84Ni8Y8 alloys were investigated, the annealing treatment of Al84Ni8Y8 amorphous alloy was carried out under a high magnetic field of 12T. The thermal stability of alloys, the change of magnetism and the effect of high magnetic field on crystallization were analysed.The as-spun Al90Ni2Y8 ribbons have a microstructure of nano-Al crystals dispersed in amorphous matrix, and as-spun ribbons of Al80Ni12Y8 have an amorphous matrix with small amount of intermetallics dispersed, other alloys form a monolithic amorphous structure by melt spinning. With increase of Ni content, the thermal stability of alloy is remarkably improved. Primary crystallization is observed in Al84Ni8Y8 alloy; both Al90Ni2Y8 and Al87Ni5Y8 alloys crystallized at a eutectic mode, the crystallization route of Al80Ni12Y8 alloy is more complicated. The magnetism of the as-spun Al90Ni2Y8 and Al84Ni8Y8 alloy are diamagnetism, and the alloys are magnetized more easily with higher Ni content. When the magnetic field reaches 5000 Oe, the specific magnetization of Al90Ni2Y8 and Al84Ni8Y8 alloy is -0.083 emu/g and -0.091 emu/g respectively. The magnetism of alloys does not change after partially crystallized, but the absolute value of specific magnetization is increased. The absolute value of specific magnetization of the Al90Ni2Y8 alloy increases to 0.231 emu/g, and that of the AlNi8Y8 alloy increases to 0.163 emu/g corresponding to a magnetic field of 5000 Oe, which means the alloys are magnetized more easily after partial crystallization.The annealing treatment of Al84Ni8Y8 amorphous alloy was carried out at 255℃,265℃for 30 min with or without a high magnetic field 12T. The results show that the high magnetic field has no obvious effect on the morphology, size, density of precipitation nano-Al crystals during crystallization procedure of these alloys.