Present work aims at investigation of the consequences of mechanical crushing prior to high pressure torsion (HPT) of the Mg-Y-Nd-Zr (WE43) alloy. Specifically the presence and size of the effect on the aging properties compared to the initially solid state and subsequent HPT are studied. For this, the WE43 alloy was mechanically crushed into particles of 0.5 –1 mm size. Than the obtained powder was formed to pellets and deformed at a pressure of 6 GPa for 10 revolutions with 1 rpm rotation speed. Thermal stability of the HPT processed alloy microstructure was studied by monitoring its microhardness and aging. Mechanical crushing and subsequent HPT processing at room temperature results in significant strengthening of magnesium alloy WE43. It was found that strengthening induced by HPT sustained to 200°C. The strength of the HPT processed alloy was additionally improved by subsequent aging. Extraordinarily high maximum value of microhardness of 1557 ± 25 MPa was reached. We suppose that crushing prior to high pressure torsion creates additional defects induced by the surfaces of individual powder particles during HPT. Additionally the surfaces of individual powder particles can act as segregation centers for rare earth elements. ... mehrThat decreases electrical resistivity due to lower precipitate dissolution and lower solid solution supersaturation.