No abstract

The flow behaviour of continuously cast AZ31 magnesium was investigated as a function of the temperature and the sample orientation. The microstructure evolution and the acoustic emission signal during the tensile tests were recorded. The results show a significant orientation dependence of mechanical properties. The degradation of mechanical properties with the increasing temperature is discussed in terms of dislocation structure evolution. K e y w o r d s : magnesium alloys, acoustic methods, tensile test

AS21 magnesium alloy (2.1Al-1Si-balance Mg in wt.%) and the alloy reinforced with short δ-Al2O3fibres (Saffil®) were deformed in compression at temperatures between 23 and 300 °C. Stress relaxation tests were performed in order to reveal features of the thermally activated dislocation motion. Internal and effective components of the applied stress have been estimated. The activation volume decreases with increasing effective stress. The values of the activation volume and the activation enthalpy indicate that the main thermally activated process in the alloy as well as in the composite is the dislocation motion in non-compact planes.