Characterization of microstructure and nanoscale phase in Mg-15Gd-1Zn (wt.%) alloy fabricated by rotating magnetic field casting

Abstract

An Mg-15Gd-1Zn (GZ151, wt.%) alloy was fabricated by rotating magnetic field (RMF) casting, and the microstructures were compared with those produced by conventional gravity casting (CGC). The results show that the RMF can cause significant dendritic fragmentation and resultant grain refinement of the as-cast alloy. Compared with the CGC, the RMF makes the distribution of secondary eutectic phase-(Mg, Zn)3Gd more uniform, but does not affect the phase types. Furthermore, the RMF contributes to the formations of kinks of long-period stacking ordered (LPSO) structures and < c + a > dislocations, which originate from the stress and strain caused by Lorenz force. Under the solution-treated condition, the RMF casting alloy presents higher content and larger size of X phases than those of CGC alloy. Interestingly, for the first time, some curved chain-like structures consisting of short rod-like nanoscale phases were found in the grains. The short rod-like nanoscale phase is composed of many γ' precipitates confined in an elliptical domain.