Fig. 1 OM a and SEM b images of the as-cast GW94 alloy and the EDX results of the skeleton phase c, the cuboid-shaped phase d, corresponding to A and B points from b, respectively

Fig. 2 XRD patterns of Mg-9Gd-4Y-0.5Zr alloy: a the as-cast, b the as-solutionized (510 °C for 6 h)

Fig. 3 a Threshold of XRT result showing the Mg24(Gd,Y)5 in the as-cast alloy and b the four biggest Mg24(Gd,Y)5 in a

Fig. 4 In-situ X-ray tomography (XRT) images of the as-cast alloy a-c and under solutionized conditions (510 °C for 0.5 h) d-e: a, d the 3D reconstruction of the sample, b, e interior showing segregated GBs with high content of Gd, Y elements (in grayscale), c, f the same cross sectional slice (in RGB bitmap)

Fig. 5 OM images of GW94 alloy solution heat treated at a 500 °C for 2 h, b 500 °C for 8 h, c 500 °C for 16 h, d 510 °C for 2 h, e 510 °C for 8 h, f 510 °C for 16 h, g 520 °C for 2 h, h 520 °C for 8 h, i 530 °C for 8 h

Fig. 6 SEM images of GW94 Mg alloy solid solution-treated at a 500 °C for 6 h, b 500 °C for 8 h, c 510 °C for 2 h

Fig. 7 Grain size variation with solution treatment time at different temperatures

Fig. 8 Area fraction of the cuboid-shaped phase in Mg-9Gd-4Y-0.5Zr alloy under different solution temperatures and time

Fig. 9 SEM images in back scattered electron (BSE) mode of this alloy solution-treated at a 510 °C for 6 h, b 520 °C for 6 h, c 565 °C for 30 h

Fig. 10 SIMS results of a Mg+, b Y+, c Gd+, d H-

Fig. 11 a SEM image of the GW94 sample after solutionized at 520 °C for 6 h and element distribution of b Mg, c Gd, d Y using EDX

Fig. 12 Mechanical properties of the as-cast and as-solutionized (at 520 °C for 6 h) GW94 Mg alloy