MECHANICAL-PROPERTIES OF ZBLAN GLASSES

Elastic moduli (E, G, K, nu) of various ZBLAN glass compositions have been determined using pulse echo ultrasonic technique. Vickers microha rdness, H(v), was measured under 100 g load and also determined system atically as a function of the load (30-125 g) for a ZBLAN11.6 composit ion submitted to different surface treatments such as storage in dry a nd wet atmosphere and optical polishing. In all cases, H(v) increases with load until reaching an almost constant value H(v) congruent-to 20 0 kg/mm2 for load > 100 g. The hardness variation with load is similar for as-prepared glasses stored in dry or wet atmosphere but is more p ronounced for samples with a polished surface. The results are explain ed by a model which assumes that H(v) is determined by the weighted av erage of plastically deformed volumes in a surface layer and in the bu lk. The model allows one to estimate their microhardness and the thick ness of the surface layer.