Degradation of AlMg2 aluminium alloy caused by cavitation - An effect of cavitation intensity

Investigations of an influence of various cavitation intensity on the cavitation erosion of AlMg2 alloy is presented. In order to learn an effect of low- and high-amplitude pulses on material degradation, long- and short lasting tests were performed. Linear correlation between the cavitation load and mean depth of penetration rate of AlMg2 alloy in the long-lasting test occurs. Presence of particles of intermetallic precipitations in AlMg2 alloy accelerate the erosion. Changes of hardness during the short-lasting test are correlated with cavitation intensity. The exposition of AlMg2 alloy to cavitation of J = 26 kW/m(2) causes an increase of hardness that started with the beginning of the short-lasting test and was continued over the whole test. A decrease of cavitation intensity caused a delay in the beginning of the hardness increase, a decrease of rate of surface work-hardening and a decrease of hardness during the last minute of the short-lasting test. The dislocation investigations showed that the dense dislocation network, low-angle boundaries developed in the top layer of AlMg2 alloy, which was exposed to cavitation intensity J = 11 and 5 kW/m(2), but in deeper layers the dislocation structure of dynamic recovery was observed. In the case of exposition of AlMg2 alloy to cavitation intensity J = 0.03 kW/m(2), the structure of dynamic recovery is observed in the top layer. With an increase of cavitation intensity increases density of dislocations in the top layer and the depth, at which the dynamic recovery structure occurs.