Investigation of Effect of Mechanical Vibration During ‎Solidification on Microstructure and Wear Properties of Zn-4Si ‎Composite

In this study the effect of mechanical vibration (20 Hz, 40 Hz, and 60 Hz) during solidification on microstructure, hardness, and dry sliding wear resistance of Zn-4Si composite was studied. According to the results, Si addition led to the formation of primary Si (SiP) and eutectic Si (SiE) in the microstructure. This increased the hardness of Zn matrix from 30 BHN to more than about 60 BHN. However, uneven distribution (agglomeration) of SiP particles resulted in uneven hardness within the composite matrix. Applying the mechanical vibration during the solidification of composite improved the SiP particle distribution and refines them. According to the pin-on-disk sliding wear results, at the applied pressures of 0.25, 0.5, and 0.75 MPa, the sliding wear resistance of the modified composite (at the 60 Hz frequency) is higher than that of the as-cast composite by 50, 60, and 65%, respectively. Moreover, at the applied pressure of 0.75 MPa the average friction coefficient of mechanically-vibrated composite (60 Hz) is lower than that of as-cast composite by about 23%. Based on worn surface and wear debris analyses the substantial improvement of wear resistance in modified composites can be attributed to the improved tribolayer stability due to the strengthening effect of hard Si particles on the substrate material.