Fig. 1. Optical microstructures of (a) non-HIPed and (b, c, d) HIPed GW63 alloys in cast-T6 condition. Black and white arrows indicate the shrinkage porosities and second phases in Fig. 1a, respectively. Interested microstructures in the rectangles are magnified and embed in Fig. 1(b, d).

Fig. 2. XRT observation results of (a) non-HIPed and (b) HIPed GW63 alloys in as-cast condition. (c, d) are the partially enlarged view of (a, b), respectively (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article).

Fig. 3. Engineering stress-engineering strain curves of GW63 alloys in (a) non-HIPed and as-cast, (b) HIPed and as-cast, (c) non-HIPed and cast-T6 and (d) HIPed and cast-T6 condition. The stresses at which the quasi in-situ tensile test was paused for OM observation are labeled as green stars with stress values in Fig. 3(b) (UTS: ultimate tensile strength, YS: yield strength, EL: elongation-to-failure).

Fig. 4. (a) Secondary electron (SE) image and (b) backscatter electron (BSE) image of HIPed sample in cast-T6 condition at the same location. (c) SE image and (d) BSE image of non-HIPed sample in cast-T6 condition at the same location. EDX observation results of shrinkage porosity with (e) high and (f) low content of rare-earth (RE) elements on the surface in non-HIPed and cast-T6 sample.

Fig. 5. SEM image and EDX element mappings of shrinkage-porosity-close lines in HIPed and as-cast sample (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article).

Fig. 6. (a) Optical microstructure and corresponding EBSD observation results of HIPed and as-cast sample containing shrinkage-porosity-close lines: (b) inverse pole figure map, (c) local misorientation map and (d) line profiles of the misorientation angle along the black arrow AB in Fig. 6(b) (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article).

Fig. 7. (a) Optical microstructure of sample with partially closed shrinkage porosity and (b) schematic of shrinkage porosity closure.

Fig. 8. Evolution of shrinkage-porosity-close lines during quasi in-situ tensile test in as-cast condition. The crack nucleating around second phases is indicated in rectangles. The stresses at which the quasi in-situ tensile test was paused for OM observation are labeled as green stars with stress values in Fig. 3(b).