Development of metastable aluminum alloy coatings and parts for automotive applications

Abstract

In this study, a metastable Al-Fe-V-Si alloy powder was produced by rapid solidification using the gas atomization process. The alloy composition was chosen for its mechanical properties at elevated temperature for potential applications in internal combustion gasoline engines. The microstructural properties of the Al-Fe-V-Si powder were determined through transmission electron microscopy imaging and selected area electron diffraction indexing, energy dispersive spectroscopy, X-ray diffraction and differential scanning calorimetry. Three distinct microstructures were observed as well as two different phases, namely a Al13(Fe,V)3Si silicide phase and a metastable (Al,Si)x(Fe,V) micro-quasicrystalline icosahedral (MI) phase. The metastable MI phase was determined to be thermally stable up to 380°C, after which a phase transformation to silicide occurs. The Cold Gas Dynamic Spraying (CGDS) process was used to produce coatings of the alloy. This spray process was selected due to its relatively low operating temperature, thus preventing significant heating of the particles during spraying and as such allowing the original microstructure of the feedstock powder to be preserved within the coatings. Coatings were produced by CGDS using Helium and Nitrogen as propellant gases. The coatings microstructure was investigated using scanning electron microscopy and transmission electron microscopy analyses. The mechanical properties of the coatings were then evaluated through bond strength testing and microhardness testing.