Mechanical and nanomechanical characterization of Al 2014-ZrO 2 /TiC surface composites fabricated via underwater friction stir additive manufacturing

This study aims to explore fabrication and mechanical characterization of a 3-layer surface composite fabricated using underwater friction stir additive manufacturing (UFSAM) of Al2014-ZrO 2 /TiC material. The process was performed with different rotational speeds (1000, 1100 and 1200 rpm) and transverse speeds (40, 50 and 60 mm/min). The fabricated specimens were tested for the tensile strength and Vickers hardness, for the tensile strength and Vickers hardness, which were maximum at 446 ± 4.6 MPa and 156 ± 3.5 HV, respectively, at the optimum values of 1100 rpm rotational speed and 50 mm/min. The following nanomechanical properties were obtained hardness (138 ± 4.5 to 156 ± 3.5HV), elastic modulus (72.4 to 80.6 GPa), elastic recovery (23.8 to 30.7%), H/E ratio (0.0250 to 0.0269), H 3 /E 2 ratio (0.00113 to 0.00166), maximum penetration depth (hmax = 288 nm), and residual/final depth (hf-186 nm). The effect of the strain rate on the indentation response was also investigated ranging from 0.005 to 1.000 s -1 . An indentation size effect (ISE) was also noticed at all strain rates. The underwater processing environment further promoted rapid heat dissipation, which restricted excessive grain growth and contributed to microstructural refinement. A series of jump strain-rate tests showed a typical sawtooth-type hardness response, with small, instantaneous jumps in hardness with each increase in strain rate, suggesting strain-rate sensitivity in the deformation mechanism. Microstructural assessment using the SEM micrographs revealed a uniform array of nanoindentation impressions and fair distribution of ZrO 2 /TiC reinforcement particles in the Al 2014 matrix.