Comprehensive study of microstructural evolution and strengthening mechanism of high-performance pure copper prepared by blue laser metal deposition (B-LMD)

The high absorption of the copper to the blue laser provides an alternative method to circumvent the laser reflection of laser metal deposition (LMD) of pure copper. In this work, blue laser metal deposition (B-LMD) was used to prepare pure copper parts. The B-LMD pure copper tracks fabricated using the optimum processing parameter have well bonding with the substrate, consisting of fine equiaxed grains with an average size of 2.8 μm, and exhibit the highest microhardness of 133.21 HV0.2. The pure copper deposit fabricated by the optimum processing parameter exhibited the highest relative density (97.9 % ± 0.2 %) and microhardness (103.05 ± 4.37 HV0.2). Additionally, the microstructure of the B-LMD pure copper deposit is showing a bimodal grain structure with columnar grains at the melt pool boundary and fine equiaxed grains at the center. The B-LMD pure copper deposit exhibits excellent mechanical properties, with an ultimate tensile strength of 244 ± 9 MPa, yield strength of 158 ± 6 MPa, and a fracture elongation of 14.7 ± 0.8 %. The superior mechanical properties are primarily attributed to grain refinement strengthening and dislocation strengthening. The high performance of B-LMD pure copper demonstrate the potential of the blue laser as an effective alternative energy source for fabricating high-performance pure copper components.