Influence of friction stir processing on wear behavior of nanosized SiC reinforced AA5083 nanocomposites developed by stir casting

In the rapidly advancing field of high-strength aluminium nanocomposites for various structural applications, sliding contact of components frequently causes wear leading to safety concerns. Friction stir processing (FSP) is an efficient route to improve microstructural features of nanocomposites by refining grains and uniformly dispersing nanosize reinforced particles. In this study, tribological properties were assessed by using a pin-on-disk tribometer for the AA5083 nanocomposites (reinforced with 1-3 wt% nanosize SiC particles), produced by bottom pouring stir casting followed by FSP at room (RT) and cryogenic (cryo) temperatures. Among all the RT-FSPed samples, the 2 wt% nanocomposite showed uniform distribution of nanosize SiC (n-SiC) particles, leading to finer equiaxed grains (similar to 4 mu m) with higher yield strength (224 MPa) & hardness (84 HV) as compared to the AA5083 sample (152 MPa, 75 HV, similar to 6 mu m grains). The 2 wt% RT-FSPed sample exhibited similar to 48 % improvement in specific wear rate (SWR) of 2.98 x 10(-5) mm(3)N(-1) m(-1) & COF of 0.43, as compared to the as-cast AA5083 alloy (5.76 x 10(-5) mm(3)N(-1) m(-1) & COF of 0.52) due to its increased strength and hardness. Further, cryo-FSPed 2 wt% nanocomposite achieved more uniform distribution of n-SiC particles, resulting in further refined matrix grains (similar to 2 mu m) accomplishing superior wear resistance (SWR: 2.67 x 10(-5) mm(3) N-1 m(-1)), higher YS (230 MPa), and hardness (89 HV). Analysis of worn-out surfaces confirmed that the delamination, abrasion, and adhesion are the dominant wear mechanisms, correlating well with wear debris analysis. The worn-out cryo-FSPed 2 wt% sample exhibited the lowest average surface roughness of 1.972 mu m and sub-surface depth of similar to 12 mu m as compared to the as-cast AA5083 alloy (3.861 mu m & similar to 58 mu m). Surface topographic features were also confirmed through AFM analysis.