In situ HVEM studies on the effects of electron-irradiation on the thermal stability of Ni-based amorphous alloys

Abstract

In situ high voltage electron microscope (HVEM) studies on the thermal stability of splat-cooled Ni-based amorphous alloys were made and three kinds of accelerated crystallization modes were observed during bombardment by focused 1000 keV electrons. In one case the crystalline grains induced by irradiation were coarser near the edge of the irradiated region (IR) than in other parts. This type of crystallization was observed in Ni₇₅B₁₇Si₈ and Ni₇₅B₁₅Si₈C₂ amorphous alloys subjected to a continuous increase in temperature of irradiation. The second case was one where there was no appreciable difference in size distribution of the crystalline grains throughout the IR. This type was observed in a Ni₈₀P₁₀B₁₀ amorphous alloy which again was subjected to a continuous increase in irradiation temperature and also observed in Ni₇₅B₁₇Si₈ amorphous alloy irradiated during isothermal annealing. In these two cases, the crystalline grains induced during irradiation did not cover the whole of the IR before crystallization started in the unirradiated region. In the third case, however, the amorphous phase completely disappeared from the IR before crystallization in the unirradiated region occurred. This type of crystallization was observed in Ni₈₀P₂₀ amorphous alloy whilst the temperature was being increased continuously during irradiation.