Abstract
In this study, we investigated the microstructures and mechanical properties of Mg-6Gd-1Er-0.5Zr (GE61K) sheets. The results show that the rolling temperature has a remarkable influence on microstructures, age-hardening responses and mechanical properties of GE61K sheets. The microstructures varies with the increase in rolling temperatures, i.e. microstructures were dominated by the mixture of dynamic re-crystallized (DRXed) grains and un-DRXed grains at 300 degrees C, by DRXed grains at 350 degrees C, and by un-DRXed grains at 400 degrees C and 450 degrees C. Rolling at 300 degrees C leads to a formation of the bimodal microstructure which contains equilibrium Mg-5(Gd, Er) precipitates and a large number of dislocations. These dislocations leads to a formation of novel chain-like precipitates which comprise dominant beta', beta'(F) (or beta'(T)), tail-like "hexagonal ring" layers, individual "zig-zag" chain and individual "hexagonal ring", eventually improving age-hardening responses. The chain-like precipitates are beneficial for achieving a good strength-ductility balance by dividing the matrix into nano-scale units and forming subsequent honeycomb structures. As a result, the R-300 degrees C sheet shows good mechanical properties, i.e. ultimate tensile strength (UTS) of 367 +/- 3 MPa, yield strength (YS) of 349 +/- 4 MPa and elongation (EL) of 9.1 +/- 1.5%, respectively. However, such strength-ductility balance is destroyed sharply as soon as the rolling temperature increases to 400 degrees C because of the microstructure variations. (C) 2021 Elsevier B.V. All rights reserved.
NSTL
Elsevier