Effect of post-processing heat treatments on the mechanical properties of alsi10mg alloy produced by selective laser melting

Date

2024-9-06

Author

Özlen, Beril

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This study examines the influence of post-processing methods on the mechanical properties of AlSi10Mg alloy components manufactured using Selective Laser Melting (SLM). The investigation aims to compare two crucial parameters across four different experimental groups: the effect of heat treatment and surface condition. AlSi10Mg specimens were fabricated with different geometrical tolerances to evaluate the effect of surface conditions by machining. Due to the inherent nature of the SLM process, post-processing heat treatments become necessary to eliminate the undesired effects of rapid solidification and temperature gradient. The experimental design systematically evaluated the impact of post-processing heat treatments, including stress relieving and direct aging, on the resultant microstructure and mechanical behavior. Direct aging is a promising treatment, yet little research has been done on how it affects the fatigue life of SLM-produced AlSi10Mg alloy. In order to provide a thorough comparison, the four-parameter Weibull function has been used for the determination of the shape of the S-N curves to evaluate the fatigue behavior of all experimental groups. After the completion of the heat treatments, it has been revealed that both stress relieving and direct aging heat treatments successfully preserved the relatively fine melt pool structure of the SLM method while promoting the precipitation of eutectic Si as the strengthening phase. The average microhardness value was ~29% higher for stress relieving compared to direct aging, reaching 137 HV. This shows that stress relieving heat treatment is closer to the peak point of precipitation sequence without disrupting the microstructure, where direct aging possibly resulted in the overaging of AlSi10Mg specimens. On the other hand, fatigue test results revealed comparable behavior between the two heat treatment groups, which is potentially linked to the precipitation of nano-sized Si particles which are not present in the as-built state. Although direct aging specimens exhibited lower fatigue life compared to stress relieved specimens for the machined parts, the S-N curve indicated that both treatments would yield superior results compared to conventional T6 heat-treated and cast counterparts, if the surface finish were identical.

Subject Keywords

Alsi10mg, Selective laser melting, Post-processing, Surface condition, Fatigue life determination

URI

https://hdl.handle.net/11511/111538

Collections

Graduate School of Natural and Applied Sciences, Thesis