New method of stress-free dilatometry to examine the structural relaxation of metallic glasses

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Abstract
A new type of dilatometer has been constructed which avoids any mechanical stress on the ribbon-shaped specimen and which measures the length change directly on the specimen on the furnace avoiding any transfer elements. The concept applies sensitive photometric measurement of the width of a slit machined into a reference plate of known material, which is partially covered by the end of the specimen ribbon clamped at the other end. The change of the width of the slit is a measure of the relative length changes of specimen and reference plate. The set-up has been tested by measuring known material and it is applied to monitor the structural relaxation of metallic glass ribbons which increase in density by atomic rearrangement in the amorphous state as well as during crystallisation. Examples for commercial FeNi-based amorphous alloys are given.