Understanding Ni-modified AlSi10Mg alloys from slow to rapid solidification

Abstract

Al-Si-Mg alloys are widely employed in a variety of industries, including aerospace, automotive, and microelectronics. This is because of its low density, acceptable mechanical properties, acceptable corrosion resistance, and inexpensive application cost. Because of its advantageous fluidity, limited solidification interval, and low volumetric contraction, Al-(9-11) wt.% Si-(0.2-0.5) wt.% Mg casting alloys have been employed in Laser-Powder Bed Fusion (LPBF) printing techniques. Despite being used as commercial alloys, their mechanical properties still need to be improved. In line with this, the current focus of aluminum-based alloys development for additive manufacturing is mostly on the modification of commercially available alloys. One of the possibilities is the reinforcement of cast alloys that may be processed using additive manufacturing technologies. Nickel is used as an alloying element in this study to generate the Al3Ni intermetallic, which is distinguished by its improved strength. Furthermore, the thermal stability of the Al3Ni may be a benefit, particularly for high-temperature applications. Under such context, the present study aims to investigate the solidification under low and high cooling rates of three alloys: AlSi10Mg-1Ni, AlSi10Mg-2Ni, and AlSi10Mg-3Ni (wt.%). Samples were obtained by directional solidification (DS) and laser surface remelting (LSR) and the cooling rates were calculated for both DS samples and with extrapolation for the more refined LSR samples as well as with the use of models from the literature. With the increase in Ni content, the Al3Ni mass fraction increased from 3% to 5% and then to 7.5%, according to CALPHAD computations. The growth rate of the DS samples was lowered in the direction of Ni addition: 1 Ni > 2Ni > 3 Ni. SEM data will be presented, with a focus on the rapid solidified melt pool samples and their features.