Identification and modelling of applicable wear conditions for stir cast Al-composite

Santanu Sardar,Debdulal Das,Santanu Kumar Karmakar

doi:10.1007/s40544-019-0302-6

Santanu Sardar, Debdulal Das + Show 1 more

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https://doi.org/10.1007/s40544-019-0302-6

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Abstract

A comprehensive study of the tribological performance of the Al-Zn-Mg-Cu/Al2O3 composite and its matrix alloy is presented in this paper, with a specific emphasis to identify and model the applicable wear conditions where the composite provides a minimum of 50% reduction in wear rate and 25% lowering of the friction coefficient. Two-body abrasion experiments following Taguchi L27 orthogonal design have been performed separately on alloy and composite materials, both prepared by the stir casting method. The influence of crucial control factors including silicon carbide (SiC) abrasive size, load, sliding distance, and velocity on the percentage variations of wear rates and friction coefficients between alloy and composite have been studied using the analysis of variance technique and full quadratic regression method. The dominant control factors are identified as abrasive size, load, and the interaction between abrasive size and load. This has been verified by establishing the influence of abrasive size and load on variations of wear mechanisms like microcutting, microploughing, and delamination, identified by means of in-depth characterization of worn surfaces and generated debris for both alloy and composite. The selection of applicable tribological condition for the composite has been accomplished by adopting the multi-response optimization technique based on combined desirability approach to obtain concurrent optimization of the percentage variations of wear rates and friction coefficients. Predictive models correlating the superiority of tribological performance of composite with abrasion conditions have been developed, and these are found to be accurate (errors <10%), as determined by confirmatory experiment.

Highlights

The urge to reduce greenhouse gas emissions and the ever-increasing cost of fossil fuel have led towards the development of weight-saving components for aerospace and automotive industries, where aluminum and its alloys are favored because of their higher strength-to-weight ratio [1, 2]
The present study aims to compare tribological characteristics between the Al 7075 alloy reinforced with 20 wt% Al2O3 particles and its unreinforced matrix alloy based on the experimental layout of the Taguchi L27 orthogonal array
The tribological performance of the Al-Zn-Mg-Cu/ Al2O3 composite material with respect to its matrix alloy pertaining to two-body abrasion has been studied in view of achieving improved wear resistance and a reduced coefficient of friction (COF) following the Taguchi L27 orthogonal experimental layout

Summary

Introduction

The urge to reduce greenhouse gas emissions and the ever-increasing cost of fossil fuel have led towards the development of weight-saving components for aerospace and automotive industries, where aluminum and its alloys are favored because of their higher strength-to-weight ratio [1, 2]. The relatively poor wear resistance property of aluminum alloys limits their applications in tribological fields [3, 4], which paves the way for exploring discontinuous ceramic reinforced aluminum matrix composites (AMCs) because of their excellent wear and corrosion resistance abilities in addition to improved mechanical properties over unreinforced Al alloys [5]. Alloy is widely employed in aircraft structural components (e.g., wings, horizontal, and vertical stabilizers) where fatigue resistance, compressive strength, and tribological properties remain crucial issues [9]. Efforts have been directed towards enhancing mechanical and tribological performances of the Al 7075 alloy by incorporation of discontinuous ceramic particles in the manufacture of automotive components such as the engine block, driveshaft, cylinder heads and liners, brake drum, and rotor [10], as well as parts of fuselage like ventral fins, exit guide vanes of engine fan, wings, and fuel access covers [6, 11], etc. Among the vast processing techniques for developing particulate reinforced AMCs, the stir-casting route is preferred for large scale application in industries, since it is convenient and cost-effective for mass production of any component with a complex geometry of reproducible structures, properties, and reasonably good matrix-reinforcement bonding [14]

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