Investigations on the Influence of Subsequent Electron Beam (EB) Remelting on the Microstructure of an Aluminium Nitride Layer Formed on an Aluminium Substrate (Part II)

Abstract

Nitriding of Al alloys leads to the formation of a thin, hard nitride layer (AlN) on the surface. A subsequent EBR can both eliminate the nitriding-related cavities under the nitride layer and increase the hardness of the substrate without melting or destroying the nitride layer. This paper deals with investigations regarding the influence of the energy/heat input on the microstructure within both the AlN layer and the remelted Al substrate. Of particular interest was the interface between the AlN and the Al substrate, which changed to a transition zone with a depth of approximately 80 µm. A range of high-resolution imaging and analytical tools for both scanning and transmission electron microscopy were used for these investigations. Based on the findings from the microstructural investigations, a schematic model was developed of the processes occurring within the nitride layer and at the interface as a result of remelting.

Investigations on the Microstructure of an Aluminium Nitride Layer and Its Interface with the Aluminium Substrate (Part I)

“…The nitriding behaviour and the influence of the nitriding conditions on the layer formation have already been investigated at a fundamental level for spray-compacted Al-Si alloys [3,4,6,33]. Within the scope of this work, different nitride layer thicknesses (for parameters see Table 1) were specifically set for the subsequent remelting experiments (see [28]). The thicker the nitride layer, the more complete the surface coverage with AlN (I. in Figure 2a-c).…”