Tribology in Industry (Sep 2016)
Dry Sliding Wear Behavior of A356 Alloy/Mg2Sip Functionally Graded in-situ Composites: Effect of Processing Conditions
Abstract
In present study, the effect of dry sliding wear conditions of A356 alloy/Mg2Sip functionally graded in-situ composites developed by centrifugal casting method has been studied. A pure commercial A356 alloy (Al–7.5Si–0.3Mg) was selected to be the matrix of the composites and primary Mg2Sip reinforcing particles were formed by in-situ chemical reaction with an average grain size of 40-47.8 µm. The Al–(Mg2Si)p functionally graded metal matrix composites (FGMMC’s) were synthesized by centrifugal casting technique with radial geometry, using two different mould rotating speeds ( 1200 and 1600 rpm). The X-ray diffraction (XRD) characterization technique was carried out to confirm the in-situ formed Mg2Si particles in composites. Optical microscopy examination was carried out to reveals the grain refinement of Al-rich grains due to in-situ formed Mg2Si particles. Scanning electron microscope (SEM) and Energy dispersive X-ray spectroscopy (EDS) techniques were carried out to reveal the distribution of phases, morphological characteristics and confirmation of primary Mg2Si particles in the matrix. The sliding wear behavior was studied using a Pin-on-Disc set-up machine with sliding wear parameters: effect of loads (N), effect of sliding distances (m) and effect of Mg on wear at room temperature with a high-carbon chromium steel disc (HRC-64) as counter surfaces. A good correlation was evidenced between the dry sliding behaviour of functionally graded in-situ composites and the distribution of Mg2Si reinforcing particles. Beside the above processing conditions, the dominant wear mechanisms of functionally graded in-situ composites have been correlated with the microstructures. The hardness and wear resistance properties of these composites increase with increasing volume percent of reinforced primary Si/Mg2Si particles toward inner zone of cast cylindrical shapes. The objective of this works was to study the tribological characteristics under dry sliding conditions of fabricated composites for automotives engine blocks and cylinder liners.
