TY - JOUR
T1 - Long-time stability of metals after severe plastic deformation
T2 - Softening and hardening by self-annealing versus thermal stability
AU - Edalati, Kaveh
AU - Hashiguchi, Yuki
AU - Iwaoka, Hideaki
AU - Matsunaga, Hirotaka
AU - Valiev, Ruslan Z.
AU - Horita, Zenji
N1 - Funding Information:
The author K.E. thanks the MEXT, Japan, for a Grant-in-Aid for Scientific Research (B) (No. 16H04539 ). This study was also supported in part by the Grant-in-Aid for Scientific Research (S) from the MEXT, Japan (No. 26220909 ) and in part by SPSU in the framework of Call 3 Project (id 26130576 for R.Z.V.). The HPT process was carried out in the International Research Center on Giant Straining for Advanced Materials (IRC-GSAM) at Kyushu University.
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/6/27
Y1 - 2018/6/27
N2 - Despite superior properties of ultrafine-grained (UFG) materials processed by severe plastic deformation (SPD), their thermal stability is a concern because of the supersaturated fractions of lattice defects. In this study, the microstructural stability of various UFG materials (2 alloys and 15 pure metals) after SPD processing through the high-pressure torsion (HPT) were investigated at room temperature for up to 10 years. While most of the metals with high melting temperatures remained stable, a softening by self-annealing occurred in pure silver, gold and copper (with moderate melting temperatures), and an unusual hardening occurred in pure magnesium, Al-Zn alloy and Mg-Li alloy (with low melting temperatures). These softening/hardening behaviors by grain coarsening were attributed to the contribution of grain boundaries to dislocation activity or grain-boundary sliding, respectively. It was shown that the self-annealing was accelerated by increasing the processing pressure and strain and by decreasing the processing temperature and stacking fault energy, due to the enhancement of stored energy and/or atomic mobility.
AB - Despite superior properties of ultrafine-grained (UFG) materials processed by severe plastic deformation (SPD), their thermal stability is a concern because of the supersaturated fractions of lattice defects. In this study, the microstructural stability of various UFG materials (2 alloys and 15 pure metals) after SPD processing through the high-pressure torsion (HPT) were investigated at room temperature for up to 10 years. While most of the metals with high melting temperatures remained stable, a softening by self-annealing occurred in pure silver, gold and copper (with moderate melting temperatures), and an unusual hardening occurred in pure magnesium, Al-Zn alloy and Mg-Li alloy (with low melting temperatures). These softening/hardening behaviors by grain coarsening were attributed to the contribution of grain boundaries to dislocation activity or grain-boundary sliding, respectively. It was shown that the self-annealing was accelerated by increasing the processing pressure and strain and by decreasing the processing temperature and stacking fault energy, due to the enhancement of stored energy and/or atomic mobility.
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U2 - 10.1016/j.msea.2018.05.079
DO - 10.1016/j.msea.2018.05.079
M3 - Article
AN - SCOPUS:85047600867
SN - 0921-5093
VL - 729
SP - 340
EP - 348
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
ER -