Plastic-deformation-driven SiC nanoparticle implantation in an Al surface by laser shock wave: Mechanical properties, microstructure characteristics, and synergistic strengthening mechanisms

Laser shock-wave-driven nanoparticle implantation (LSWNI) in alloys is a novel surface strengthening technique based on plastic deformation induced by laser shock processing and the excellent properties of hard-phase nanoparticles. In the present work, 50–100 nm silicon carbide (SiC) nanoparticles were successfully implanted into commercially pure aluminum (Al) substrates under the effect of a laser shock wave. After the implantation, stable nanoparticle-reinforced layers were fabricated, and their microstructural response and grain refinement were characterized by X-ray diffraction (XRD), focused ion beam (FIB), and transmission electron microscopy (TEM). In addition, the mechanical properties, including residual stress, nanohardness, elastic modulus, and wear resistance, were investigated. Experimental results showed that Al samples subjected to LSWNI exhibited superior mechanical properties because of the good combination between the gradient microstructure induced by plastic deformation and the gradient distribution of the implanted SiC nanoparticles along the depth direction. Therefore, the overall strengthening effect generated by the LSWNI process can be described as two different modes: (i) the gradient microstructure induced by plastic deformation contributed mainly to the enhancement of residual stress and nanohardness, and (ii) the gradient distribution of the implanted SiC nanoparticles was dedicated primarily to the improvement of the wear resistance. As indicated by the strengthening effect during the LSWNI process, three competing strengthening mechanisms, namely, SiC nanoparticle strengthening, refined grain strengthening, and dislocation strengthening, existed in the gradient-reinforced layers. The detailed contribution of each mechanism to the overall properties of the reinforced layer was determined using the modified Clyne computational model and was described herein. Finally, the wear mechanism of the reinforced layer fabricated by the LSWNI process is revealed.