Fig. 1. Image showing (a) powder size distribution and cumulative distribution of feedstock powder, the inset provides a SEM image showing the morphology of the powder and (b) as-printed parts on a stainless-steel plate.

Fig. 2. Image showing typical microstructure and phase constitution of the as-built CoCrW alloy parts. (a) Molten pool configuration, the white arrow indicates the building direction of the sample, (b) cell structures, (c) XRD pattern of the powder feedstock and as-printed samples, (d) EBSD IPF map, (e) the corresponding phase map with grain boundaries and (f) GND map. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article).

Fig. 3. Image showing (a) a bright field STEM image of the as-printed samples, the inset gives the SAD patterns obtained from the squared matrix indicating the existence of γ austenite and ε martensite. Two distinct types of nano-particles are recognized as (b) the bright particles, and (c) the dark particles. (c) Some of these two types of particles are found to associate together. The size distributions of (e) the bright particles and (f) the dark particles are statistically analyzed from over 200 particles.

Fig. 4. Image showing (a) the STEM-HAADF image of two types of particles that are associated together and (b) corresponding EDS mapping results showing their distinct chemical compositions.

Fig. 5. Image showing (a) the morphology of a spherical oxide particle, the inset provides a SAD pattern showing its amorphous nature, (b) HRTEM image demonstrating a transition boundary between the amorphous oxide and the austenite matrix. In addition, squared areas in (b) were used to obtain the detailed inverse fast Fourier transform (IFFT) images of (c) amorphous core, (d, e) crystalline structures within the transition boundary and (f) matrix.

Fig. 6. Image showing (a) a bright field TEM image of a precipitate and its corresponding SAD pattern obtained at (b) B//[-111] and (c) B//[-113]. The BCC structure can be confirmed by considering the sample stage crystallographic projection angle.

Fig. 7. Image showing (a) morphological TEM image of a precipitate, (b) 45° symmetry-related-domains substructure existing inside the precipitate, the inset gives the FTT image indicating a single domain at B//[001], (c) an 8-fold symmetric SAD pattern obtained from image in (a) and (d, e) the schematically indexed pattern and explanation of the 8-fold symmetric SAD pattern presented in (c). (For interpretation of the references to color in this figure, the reader is referred to the web version of this article).

Fig. 8. Image showing (a) representative engineering tensile curve, (b, c) morphologies of the fracture surface, where the tensile direction is indicated by the black circle, (d, e) bright-field and dark field images obtained from a region near the fracture area and (f, g) corresponding SAD patterns indicating the occurrence of strain-induced γ-ε transformation during deformation.

Fig. 9. Image showing (a, b) the fracture morphologies obtained by SEM using in-lens detector, note that the oxides inside the dimples are indicated by red arrows and (c, d) the EDS results showing chemical compositions of both nano-oxide and the matrix obtained from circled areas. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article).

Fig. 10. Image showing (a, d) microstructures in the vicinity of oxide particles after the occurrence of tensile deformation, (b, e) the transition boundary with SFs/martensite at high-resolution, the inset is the FFT patterns of the transition boundary area, (c, f) the IFFT image reconstructed showing the accumulations of dislocations within the transition boundary, (g-i) schematic illustration of crack initiation within transition boundary of an oxide particle where the dislocations accumulate.