Abstract
	The paper presents characteristic physical-metallurgical properties of selected magnesium alloys at hot deformation. Special attention was devoted to analysis of deformation conditions on microstructure and final mechanical properties. Development of microstructure has been observed from as cast state till heat treatment T4. Deformation was made by rolling and hot torsion test on alloys AZ91, AZ61 and AZ 31. After applied plastic deformation attention was paid also to share of individual types of deformation mechanisms. Twinning was confirmed as one of mechanisms that prevail at lower interposed deformations and bigger grain sizes. The differences were evident also between materials without T4, where twinning occurred at much smaller degree. As it is obvious during first three passes at rolling the changes occurred namely at original grain boundaries and only when magnitude of deformation exceeded 40% the structure changed distinctly also at other places of matrix, which is confirmed by presence of restoration processes and overall degree of their course. However, simultaneously with development of magnesium matrix during plastic deformation a precipitate was developed, segregated originally at grain boundaries (dendrites) in the form of massive particles, or in dispersed form. After completed rolling the places were visible at which occurred precipitation of ?-phase (Mg17Al12 ) in discontinuous form, or local islands of this precipitate were apparent. Torsion test has confirmed dissimilar behaviour of used alloys with respect to character of their fracture surfaces. Heat treated materials demonstrated lower mean natural resistance to deformation than materials without T4, but they had higher intensity to fracture.