Abstract
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. That decreases electrical resistivity due to lower precipitate dissolution and lower solid solution supersaturation.
Highlights
Properties of nanocrystalline metallic materials, such as mechanical characteristics, corrosion rate and others, came to the front in the last few decades
Among all the methods of obtaining nanocrystalline alloys, high pressure torsion (HPT) holds a specific place. It belongs to the severe plastic deformation (SPD) methods and demonstrates a number of advantages compared to its competitors
Doping with rare earth metals (REM) improves the corrosion resistance of magnesium [2], and increases its strength. Another method of improving the strength characteristics is SPD, which leads to the formation of ultrafine-grained structure (UFG) in magnesium and its alloys [3]
Summary
Properties of nanocrystalline metallic materials, such as mechanical characteristics, corrosion rate and others, came to the front in the last few decades. Among all the methods of obtaining nanocrystalline alloys, high pressure torsion (HPT) holds a specific place It belongs to the severe plastic deformation (SPD) methods and demonstrates a number of advantages compared to its competitors. Another method of improving the strength characteristics is SPD, which leads to the formation of ultrafine-grained structure (UFG) in magnesium and its alloys [3] This structure provides significant hardening [3 – 6], and leads to an increase in corrosion resistance and a decrease in gas evolution. The need for such investigation was explained in our previous work It demonstrated the possibility of producing a metal-ceramic composite by introducing oxide particles of various metals into the WE43 alloy and processing it by HPT [7]. For that reason distinguishing the strengthening effect of crushing the alloy and oxide particles introduction is needed for deeper understanding of our work
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