Effect of Zn additions on the age-hardening of Mg-2.0Gd-1.2Y-0.2Zr alloys
Abstract
We have investigated the microstructures of age hardened Mg-2.0Gd-1.2Y- xZn-0.2Zr (x = 0, 0.3, and 1.0) (at.%) alloys to understand the remarkable age-hardening and unusual plastic elongation behavior. The age-hardening of the alloys occurs through the sequential precipitations of β‧ and β 1 phases. The β 1 phase heterogeneously nucleates at the interface of the β‧ phase, and relaxes strain fields around the β‧. Although the addition of Zn degrades the age-hardening response, it causes the discontinuous precipitation of a 14H-type long-period stacking (LPS) phase at grain boundaries as well as within grains in the over-aged condition, which enhances the maximum tensile elongation. The composition of the β 1 phase was determined to be Mg-23.3 at.% RE-9.7 at.% Zn-2.0 at.% Zr (RE: rare-earth, Gd and Y), whereas that of the LPS is Mg-5.6 at.% RE-1.8 at.% Zn-1.0 at.% Zr.
- Publication:
-
Acta Materialia
- Pub Date:
- 2007
- DOI:
- 10.1016/j.actamat.2007.02.036
- Bibcode:
- 2007AcMat..55.4137H
- Keywords:
-
- Magnesium-gadolinium-yttrium-zinc-zirconium alloy;
- Rare-earth;
- Three-dimensional atom probe;
- Precipitation