Fig. 1 Schematic of the tensile testing specimen

Fig. 2 OM image a and SEM image b showing the microstructure of the as-cast composite, and OM images showing the semisolid microstructures at the edge c and center d regions of the ingot (heated for 60 min at 600°C)

Fig. 3 Temperature variation in the center of the ingot with heating time at 600°C

Fig. 4 OM micrographs of the in situ Mg2Sip/AM60B composites thixoforged under heating for different durations at 600°C: a center region, 50 min; b edge region, 50 min; c center region, 60 min; d edge region, 60 min; e center region, 70 min; f edge region, 70 min; g center region, 90 min; h edge region, 90 min; i center region, 120 min; j edge region, 120 min

Fig. 5 SEM images in the center regions of the composites thixoforged under reheating at 600°C for 50 min a, 60 min b, 70 min c, 90 min d

Fig. 6 Variation of the β phase amount with reheating duration

Fig. 7 OM images of the center regions of the composites thixoforged under reheating for 50 min a, 60 min b, 70 min c, 90 min d, 120 min e

Fig. 8 OM micrographs of the composites thixoforged under reheating for different durations and then solution treated for 1 h at 430°C: a 50 min; b 60 min; c 70 min; d 90 min; e 120 min

Fig. 9 Variations of UTS and elongation with reheating duration

Fig. 10 Fractographs of composites thixoforged under different reheating durations at 600°C: a 50 min; b 60 min; c 70 min; d 90 min; e 120 min

Fig. 11 Side views of composite fracture surfaces thixoforged under different reheating durations at 600°C: a 50 min; b 60 min; c 70 min; d 90 min; e 120 min

Fig. 12 Typical fractographs and fracture surface side views of the composites: a fragmented Mg2Si particles; b side view of fragmented Mg2Si particle of the composite thixoforged under reheating for 60 min; c Mg2Si/matrix interface debonding of the composite thixoforged under reheating for 70 min; d Mg2Si clusters in the composite thixoforged under reheating for 120 min