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Effect of Numbers of Turns of High‐Pressure Torsion on the Development of Exceptional Ductility in Pure Magnesium
Author(s) -
Figueiredo Roberto B.,
Pereira Pedro Henrique R.,
Langdon Terence G.
Publication year - 2020
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201900565
Subject(s) - materials science , magnesium , flow stress , crystal twinning , torsion (gastropod) , grain size , grain boundary strengthening , metallurgy , microstructure , ductility (earth science) , plasticity , slip (aerodynamics) , severe plastic deformation , elongation , grain boundary , composite material , thermodynamics , ultimate tensile strength , medicine , creep , surgery , physics
The low ductility of magnesium at room temperature is usually attributed to an insufficient number of independent slip systems. Recent research has shown that refining the grain structure of pure magnesium promotes a breakdown in the Hall‐Petch relationship at low strain rates and may lead to the development of exceptional ductilities. This report describes the evolution of microstructure and the mechanical behaviour of pure magnesium using different amounts of imposed plastic deformation by high‐pressure torsion (HPT). It is shown that the initial coarse grains undergo twinning followed by a gradual grain refinement. The flow stress at low strain rates decreases as the grain size is reduced, thereby confirming an inverse Hall‐Petch behaviour. The elongation to failure increases with grain refinement and elongations over 300% are achieved after 1/2 turn of HPT. These experimental data agree with a model for the low temperature deformation behaviour of fine‐grained pure magnesium.