Microstructure and Wear Resistance of Laser-Treated and Slow Cooled AlSi10Mg-(x)Ni Alloys

Abstract

This study examined the solidification features and wear of AlSi10Mg(-Ni) alloy samples generated under various conditions. Additions were varied from 0 to 3 wt% Ni while maintaining Si and Mg contents. All samples were directionally solidified (DS) and laser treated using surface laser remelting (LSR). Both DS and LSR samples were characterized by a number of methods, including the following: thermal analysis, optical microscopy, stereomicroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), wear tests, and Vickers hardness. Ranges for cooling rates, dendritic spacing and hardness, respectively, were from 0.4 to 13.3 K/s, from 77 to 388 μm, from 71 to 93 HV for the DS samples and from 4.3 × 104 to 8.7 × 104 K/s, from 1.0 to 2.0 μm, and from 114 to 143 HV for the LSR (100 J/mm2). The solidification kinetics had a large impact on the solidified samples, allowing a representative range of microstructures and morphologies to be examined in terms of wear. The 1% Ni alloy had the highest wear resistance among all the DS samples under slow cooling and the short-term wear test (10 min/0.5 N), while the LSR samples showed similar wear resistances regardless of the Ni content. The uniform dispersions of Si and Al3Ni forming intercellular dense walls at the top of the laser molten pool together with their rod-like morphologies and reduced dendrite spacing of less than 2 μm, improved bonding with the matrix, resulting in higher and more consistent wear resistance of the laser treated surfaces.