Microstructure, Mechanical Properties, Creep and Corrosion Resistance of Mg-Gd-Y-Zr(-Ca) Alloys

Abstract

The microstructure, mechanical properties, creep and corrosion resistance of Mg-Gd-Y-Zr(-Ca) alloys were studied. Small additions of 0.4-0.6 wt% Ca to Mg-(9-10)Gd-3Y-0.4Zr(wt.%) alloys led to a slight improvement in creep resistance and a remarkable increase in corrosion resistance, but an obvious decrease in elongation to fracture. UTS and TYS of the Mg-Gd-Y-Zr(-Ca) alloys are obviously higher than those of WE54, especially in the temperature range from room temperature to 200 oC. TEM images and corresponding energy dispersive x-ray spectra showed that the Ca element primarily segregated to the grain boundaries and existed in the cuboid-shaped particles with a trace concentration, and the small addition of Ca had no obvious effect on the orientation, morphology, and distribution of β′ phase, which is responsible for the peak hardness in Mg-Gd-Y-Zr alloys.

High cycle fatigue behavior of different regions in a low-pressure sand-cast GW103K magnesium alloy component

“…Especially, the b9 phase is the main strengthening phase in T6 treated GW103K alloy. 5,6,11 In the present study, the grain size of different regions is almost the same due to the reasonable layout of chill blocks. These chill blocks lead to similar cooling rate of different regions, and the grain size is all ;70 lm as a result.…”

“…It indicates that the cast GW103K magnesium alloy mainly consists of a-Mg solid solution and Mg 24 (Gd,Y) 5 phase. 6 After T6 heat treatment, the eutectic phases have almost dissolved into the matrix as shown in Fig. 3(b).…”

“…According to Ref. 6, the microstructure of the T6 treated alloy mainly consists of a-Mg, c, and b9 (Mg 5 (Gd,Y) precipitates). The average grain sizes of the different regions in the T6 treated GW103K magnesium alloy are shown in Table II.…”

“…[1][2][3][4] It has been reported that the recently developed Mg-Gd-Y-Zr magnesium alloys showed considerable precipitation strengthening, leading to improved specific strength at both room and elevated temperatures, and better creep resistant than conventional Al and Mg alloys. [5][6][7] Thanks to the high performance of Mg-Gd-Y-Zr magnesium alloys, much attention is paid to produce complicated structures by these alloys in a sand mold. Different parts of a casting may receive different chemical compositions, heat treatments, and microstructures during cooling especially for the large scale castings whose size is up to meters, which can affect the tensile strength and fatigue strength.…”

In Situ Investigation of Microstructure Evolution during Solidification of Mg10CaxGd (x=5, 10, 20) Alloys

“…However, the exact nature of this ternary phase is yet to be elucidated, He et al [10] investigating the eect of 0.40.6 wt% Ca addition to a Mg10Gd3Y0.4Zr (wt%) found that new cuboidal type precipitates were found at grain boundaries containing Gd, Y and Ca. In Mg3.8Zn2.2Ca (wt%) alloys addition of Gd did not aect the microstructure, especially the solid-state precipitation, during heat treatments, but had a slight inuence on the mechanical properties.…”