Fig. 1 X-ray tomography characterisation and analysis of the pores in the as-fabricated TiB2/Al-Cu composite: a three-dimensional visualisation of pores; b the histogram of pores equivalent diameters shown in logarithmic scale; c histogram of porosity sphericity shown in logarithmic scale; and (d) sphericity versus equivalent diameter, the colour scale indicates the number of pores at certain size and sphericity. The red arrows indicate the largest pore in the section

Fig. 2 EBSD map results of a melt pool structure in the band contrast map of as-fabricated LPBF TiB2/Al-Cu composite; b IPF map, with equiaxed grains with 0.86 µm average size and weak texture, the melt pool boundary indicated by white dash line; c pole figure of b; d subset d of IPF map b, e subset e of IPF map b; f KAM and grain boundary map with even misorientation distribution; g grain size distribution calculated from IPF map b; and h misorientation distribution

Fig. 3 Correlative electron microscopy (CEM) of LPBF TiB2/Al-Cu composite: a 3D reconstruction result of backscatter imaging; b 2D microstructure with TiB2 indicated by yellow arrows, red dash lines; and c EDS map where the bright contrast area is Cu-rich, while TiB2 clustered as a flower shape

Fig. 4 SEM imaging of a TiB2 particle found in powder, b TiB2 particle cluster in as-fabricated composite, c and d three-dimensional reconstruction of TiB2 (red colour) and Al2Cu precipitates (yellow colour)

Fig. 5 STEM characterisation of LPBFed TiB2/Al-Cu composite: a fine TiB2 particles (around 50 nm) in α-Al grain, while large TiB2 particles around 500 nm size at grain boundary (indicated by blue arrows), and Al2Cu precipitates (indicated by yellow arrows) at the grain boundary (indicated by white dash lines); b Al2Cu precipitating particles around 150 nm and grain boundary (indicated by white arrows), EDS mapping at grain boundary showing slightly Cu-, Ag- and Mg-rich, and the fine particles in Al2Cu precipitate is Ag- and Fe-rich (indicated by red and blue arrows, respectively)

Fig. 6 TEM bright-field image on fine TiB2 particles in α-Al matrix, with d001 plane distance of 3.2 Å

Fig. 7 STEM characterisation reveals nanosize particles within the Al matrix: a HADDF image with bright particles of a few nm in Al matrix and b higher-magnification image and the diffraction pattern of the matrix nanoparticles and GP zone

Fig. 8 Strength-strain curves of as-fabricated LPBF TiB2/Al-Cu composite samples under standard tensile and in situ tensile tests

Fig. 9 Diffraction of LPBF TiB2/Al-Cu composite during tensile loading: a diffraction peaks and presents phases and b lattice strain versus stress including elastic deformation stage, transition period (260 MPa-320 MPa), and stress redistribution during the plastic deformation stage

Fig. 10 In situ μCT results of porosity during tensile loading a-d, and crack development during tensile loading e-g

Fig. 11 Variation of porosity, number of pores, maximum pore diameter and average pore diameter during tensile testing

Fig. 12 Fractography of the in situ test samples after failure: a 3D volume rendering of the CT scan of the fractured specimen; b-f secondary electron images: b a large region showing relative smooth fracture surface with the crack initiation region, indicated by the white box; c the crack initiation region with some particles and smooth surface; d a zoomed-in image of box d in c; e a further zoomed-in image of box e in d; f a zoomed-in image of box f in c