Vliv tepelného zpracování a zmrazování na 12% cínový bronz – část II.

Jurči Peter - Slovak University of Technology (Slovakia)

In the present work, CuSn12 bronze was subjected to various heat treatments including solutioning, artificial aging and cryogenic treatments. The as-received bronze contained the α – solid solution and the δ – eutectoid (mixture of α – and δ – phases). Solutioning induced complete dissolution of the δ – phase. Subsequent artificial aging evoked discontinuous precipitation of ε – phase at grain boundaries. Discontinuous precipitation was accelerated by the used of cryogenic treatments. Moreover, this treatments resulted in substantial increase in the number of fine deformation twins inside the α – solid solution grains, which may act as preferential sites of continuous precipitation. Since the grain boundary diffusion is much faster than the grain interior diffusion the precipitation at grain boundaries is much more pronounced. This is reflected, for instance, in substantially increased microhardness in the nearby grain boundary regions. The hardness and yield strength were decreased by all of the applied treatments while opposite effects were recorded for the ductility and impact toughness. However, slight but undisputable effect of aging on all the mechanical properties (increase in hardness, yield strength but decrease in ductility and toughness) was determined.

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