Influence of secondary phase particles Al₂O₃/SiC on the microstructure and tribological characteristics of AA7075-based surface hybrid composites tailored using friction stir processing

Abstract

Recently, cylinder liners of automotive and aircraft engines are encountered severe wear due to piston slap occurred by the repeated sliding stroke of piston. This research focuses on providing an alternative material for cylinder liners, which can be obtained through friction stir processing on AA7075 with different weight ratios of reinforcements like Al2O3 and SiC. Friction stir processing is executed with a tool rotational speed of 1000 r/min and traveling speed of 56 mm/min at 2° tool tilt angle. The images of optical microscopy reveal the fine-grains with a homogeneous distribution of secondary phase particles and also offer decrement in particle clustering except at some localized regions. It is identified that addition of 3.7 wt.% Al2O3 + 3.0 wt.% SiC in AA7075 enhanced the microhardness about 33.96% higher than base matrix. Hence, wear resistance of the specimen is improved. Dry sliding wear behavior of specimens is analyzed using pin on disc at 20, 40, and 60 N load conditions to create the actual sliding behavior of piston on cylinder wall. Increasing the wt.% of Al2O3 particles enhanced the wear resistance of AA7075 surface hybrid composites at 20 N load due to the formation of protective tribofilm. Specimen with 3.7% Al2O3 + 3.0% SiC has better lubrication and load-bearing capacity that exhibits superior tribological behavior at 40 and 60 N. Higher Fe content of 5.44 wt.% has been obtained through spectroscopy analysis in S5, which is 8% and 6% higher than S3 (7.5% of Al2O3) and S7 (6% of SiC), respectively. The scratching action of this hard specimen on the counterpart brings more Fe content. Increase of Al2O3 particles paved the way for tribofilm formation and identified through scanning electron microscopy micrographs. The observation from worn specimens shows that finer wear debris had increased by adding more quantity of SiC particles due to abrasive wear mechanism.

Tribological and mechanical characterization of as-cast and thermal treated Al-9Si/SiC graded composite

“…These loose debris form a tribo-layer composition (MML). [64][65] Based on the obtained COF results at 55 N, it is confirmed that the values are in accordance with the tribolayer consisting Fe, Al, and oxides, which is produced out of sliding action over the counter plate. Similar observations are reported during the mono-directional dry sliding action of Al/13wt%B 4 C composites against a phenol-based brake pads.…”

Influence of Fly Ash and Emery based particulate reinforced AA7075 surface composite processed through friction stir processing

“…Fine grain size increases the hardness of the SCs based on Hall petch relation. Dispersion strengthening [36][37][38] and hindering dislocation mechanism by emery and FA reinforcements [39][40][41] is also accountable for the increased hardness. Difference in thermal expansion coefficient values of the reinforcement particulates and parent matrix brings quench hardening effect into action.…”

Numerical and experimental investigations on the effect of target thickness and solution treatment on the ballistic behaviour of AA7075 thick plates

“…10–14 , 16–21 The AA7075 grades, in particular, are widely preferred among all grades.AA7075 grades are majorly alloyed with Al-Zn-Mg-Cu elements which possess higher tensile properties, better specific strength, good corrosion resistance, good thermal conductivity, higher fracture toughness and superior energy absorbing capability. 10–16 The main problems arising in AA7075 grades during fusion welding processes are (i) solidification hot cracking and (ii) micro segregation of alloying elements in the heat affected zone (HAZ). So these grades are only recommended for solid state welding processes, like friction stir welding.…”