Abstract
The entire recrystallisation sequence and associated crystallographic texture evolution of Mg-0.8Zn-0.2Ca (wt.%) alloy was tracked using a quasi-in-situ electron backscatter diffraction (EBSD) method. Characteristic “Rare Earth” (RE) texture was formed, originating mainly from double twins and twinning-related shear bands consisting of compression and double twins. The RE textures appeared during the nucleation stage and were preserved during the relative uniform grain growth period because of solute segregation and concurrent precipitation although the alloying element content was very low. Ca and Zn co-segregated along grain boundaries with no evidence that segregation was preferred along special types of grain boundaries. The interactions between deformation microstructures, concurrent precipitation, solute drag, grain growth and texture evolution are discussed in detail. All the results indicate that Ca performs a similar role to that of RE elements in forming RE texture.
Highlights
Rare Earth” (RE) elements are expensive and strategically important and so there has been much effort to find alternatives
The dimples on the sample surfaces were introduced by final argon ion polishing using a Gatan precision etching and coating system (PECS)[11]
In addition to the low misorientations associated with low angle GBs and noise, there were peaks around 86°, 56° and 38° representing three types of twin boundaries: tension twin (TTW), compression twin (CTW) and double twins (DTW)
Summary
RE elements are expensive and strategically important and so there has been much effort to find alternatives. A weakened texture was only found in the ternary alloy They hypothesised that co-segregation of Zn and Ca atoms to the grain boundaries in the ternary alloy strongly restricted high-energy GBs mobility of the basal recrystallised grains. They stated that the formation of the weakened texture was attributed to uniform growth of recrystallised grains originating from grain boundary recrystallisation, rather than shear band recrystallisation or deformation twin recrystallisation. Stanford[31] has already shown that Ca can act in a similar manner to RE elements in texture strength evolution in extruded material because of its large atomic radius Despite these above mentioned studies, there remains a number of questions that need to be addressed. These results implied Ca played an analogous role to that of RE elements in forming recrystallisation textures during annealing
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