Effect of Heat Treatment on Microstructure and Selective Corrosion of LPBF-AlSi10Mg by Means of SKPFM and Exo-Electron Emission

Abstract

The paper deals with the evolution of the microstructure of AlSi10Mg alloy obtained by laser powder bed fusion (LPBF), as a function of the post-processing heat treatment temperature. This was approached by complementary methods including FE-scanning electron microscopy, scanning Kelvin probe force microscopy and exo-electron emission techniques. The fast cooling rate of the LPBF process as compared to traditional casting produces a very fine microstructure with high mechanical properties and corrosion resistance. However, the LPBF-AlSi10Mg alloy can be susceptible to selective corrosion at the edge of the melt pools generated by the laser scan tracks. Post-process thermal treatments of the Al alloy induce a marked modification of the silicon network at melt pool edges, in particular at high temperature such as 400 °C. It was found that this is associated to a more homogeneous distribution of Volta potential. Analysis of exo-electron emission confirms the silicon diffusion during thermal treatment. The modification of the silicon network structure of the LPBF-AlSi10Mg during thermal treatment reduces the susceptibility to selective corrosion.

Microstructural evolution and hardening phenomenon caused by aging of AlSi10Mg alloy by laser powder bed fusion

“…The amount of supersaturated solid solution of Si in α-Al can reach 2.2–2.8 at.% in AlSi10Mg alloy, which is much higher than the maximum solubility of Si of 1.4 at.% according to the equilibrium state of AlSi10Mg alloy [ [9] , [10] , [11] ]. Dimensional changes, corrosion resistance and high temperature strength derived from the characteristic microstructural morphology formed by the LBPF process have also been reported [ [12] , [13] , [14] ].…”