Selective Laser Melting (SLM) was investigated as new processing route for strongly hypereutectic AlSi alloys for thermal management applications in space industry. Processing conditions, microstructure and thermal expansion behavior were analyzed for AlSi10Mg+Si alloys with 25 wt% and 50 wt% Si fabricated by in-situ SLM of powder mixtures. For both Si compositions parts with densities ≥ 99% could be achieved using laser power ≥ 275 W and scan speeds ≥ 1500 mm/s for the alloy containing 25 wt% Si and laser power of 400 W and scan speeds ≥ 1500 mm/s for the alloy containing 50 wt% Si. Considerable refinement of primary and eutectic Si was achieved for both Si compositions due to the high cooling rates of SLM. The mean particle size for the coarse primary Si of the 50 wt% Si containing alloy was below 10 µm. Additionally, unmolten Si powder particles were observed. Measurements of the coefficient of thermal expansion (CTE) showed the tailorability of CTE with adjustment of Si content. A decrease in CTE of 43% compared to pure Al was achieved at a total Si content of 50 wt%. Experimental data was close to model calculations based on the rule of mixture and the Turner model depending on the different microstructures of the two alloy compositions.

KurzfassungNahezu alle Fertigungsverfahren führen durch inhomogene plastische Verformungen oder lokal unterschiedliche thermische Ausdehnungskoeffizienten zur Ausbildung von Eigenspannungen. Wenn diese aufgrund ihres Vorzeichens die Bauteileigenschaften ungünstig beeinflussen würden, müssen sie nachträglich abgebaut werden. Durch Einstellung geeigneter Prozessführungen können allerdings auch günstige Beeinflussungen der Bauteileigenschaften erreicht werden, sodass diese Prozessvarianten gezielt zur Optimierung von Bauteilzuständen, dem sogenannten Surface Engineering, eingesetzt werden können. Die Zusammenhänge zwischen dem Eigenspannungszustand sind Gegenstand der Arbeit. Dabei wird auf alle Hauptgruppen der Fertigungstechnik eingegangen.

In inductive heat treatment, the induction coil design plays an important role in the localization of heat generation. Therefore, the combination of an optimized coil geometry and frequency choice determines the workpiece properties and applicability of close-to-contour hardening for small parts or thin hardened layers. Additive manufacturing of copper alloys in the Selective Laser Melting (SLM) process offers a method to build coils with high design flexibility and precision. Conventional coil manufacturing methods are reaching their limitations due to the conflicting geometry specifications at the applied frequency range. In the present work, a characterization is presented and the performance of an SLM manufactured coil in MHz induction application of small surface hardened wires of steel is examined.