scholarly journals High Strain Rate Superplasticity of WE54 Mg Alloy after Severe Friction Stir Processing

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1573
Author(s):  
Marta Álvarez-Leal ◽  
Fernando Carreño ◽  
Alberto Orozco-Caballero ◽  
Pilar Rey ◽  
Oscar A. Ruano

Friction stir processing (FSP) was used on coarse-grained WE54 magnesium alloy plates of as-received material. These were subjected to FSP under two different cooling conditions, refrigerated and non-refrigerated, and different severe processing conditions characterized by low rotation rate and high traverse speed. After FSP, ultrafine equiaxed grains and refinement of the coarse precipitates were observed. The processed materials exhibited high resistance at room temperature and excellent superplasticity at the high strain rate of 10−2 s−1 and temperatures between 300 and 400 °C. Maximum tensile superplastic elongation of 726% was achieved at 400 °C. Beyond 400 °C, a noticeable loss of superplastic response occurred due to a loss of thermal stability of the grain size. Grain boundary sliding is the operative deformation mechanism that can explain the high-temperature flow behavior of the ultrafine grained FSP-WE54 alloy, showing increasing superplasticity with increasing processing severity.

2004 ◽  
Vol 821 ◽  
Author(s):  
Koji Morita ◽  
Keijiro Hiraga ◽  
Byung-Nam Kim ◽  
Yoshio Sakka

AbstractThe role of MgAl2O4 spinel particle dispersion in high-strain-rate superplasticity (HSRS) of tetragonal ZrO2 was examined by characterizing microstructural changes during deformation. The dispersed spinel particles elongate with strain along tensile direction and the elongation tends to be pronounced with increasing strain rate. In the elongated spinel particles, intragranular dislocations lying along the elongated direction were observed, suggesting that the elongation relates to the dislocation motion. The flow behavior characterized by a stress exponent of ≈ 2.0 suggests that grain boundary sliding (GBS) is the predominant flow mechanism. The dislocation-induced plasticity in the spinel particles may assist the relaxation of stress concentrations exerted by GBS, leading to HSRS in tetragonal ZrO2.


2015 ◽  
Vol 18 (2) ◽  
pp. 312-318 ◽  
Author(s):  
Genghua Cao ◽  
Datong Zhang ◽  
Fang Chai ◽  
Wen Zhang ◽  
Cheng Qiu

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