Influence of Stress Relief Annealing Parameters on Mechanical Properties and Decomposition of Eutectic Si Network of L-PBF Additive Manufactured Alloy AlSi10Mg

Abstract

This paper evaluates the effect of stress-relieving heat treatment on the AlSi10Mg alloy prepared by additive manufacturing using the Laser Powder Bed Fusion (L-PBF) with print parameters: 370 W, 1400 m/s, and 50 μm. The as-built state and four different annealing modes (240 °C/2 h, 240 °C/6 h, 300 °C/2 h, and 300 °C/2 h/water-quenched) are investigated. To determine the effect of the annealing mode on the mechanical properties of the L-PBF AlSi10Mg alloy, heat-treated samples were compared with the as-built state and with each other. The mechanical properties of the samples were determined by tensile and hardness tests. The strength in the as-built state is 488 MPa, depending on the method of heat treatment, the strength values range from 296 MPa to 417 MPa, and the HV10 hardness values are in accordance with the measured strength values. Furthermore, the microstructure of the samples was investigated by scanning electron microscopy (SEM) analysis, which was then linked to the measured mechanical properties. The composition of the microstructure of the alloy and its influence on the mechanical properties were determined by energy dispersive spectroscopy (EDS) analysis. Furthermore, the differences between the individual heat treatments in comparison with the as-built state were analyzed and the phenomenon of decomposition of the silicon network after reaching specific temperatures was discussed and confirmed. The paper evaluates the effect of dwelling time on stress relief annealing. It was found that if annealing at intermediate temperatures of 240 and 300 °C is applied, changes in structure and mechanical properties are more temperature- than dwell-time-dependent.

Mechanical properties of additively manufactured AlSi10Mg under quasi‐static and cyclic loading

“…This outcome aligns well with the mechanical findings, where the decomposition of the Si network correlates with decreased strength characteristics. Similar results were noted in the study 74 …”

Heat Treatments for Minimization of Residual Stresses and Maximization of Tensile Strengths of Scalmalloy® Processed via Directed Energy Deposition

“…While residual stress minimization is clearly needed as a treatment step, minimization must be balanced such that mechanical behavior isn’t significantly diminished. Růžičková et al explored the concept of intermediate temperature stress relief treatments to map the response of SLM-fabricated AlSi10Mg to different heat treatment factors [ 13 ]. The authors determined that heat treatment at 240 °C for 2/6 h followed by a furnace cool to 100 °C and air cooling resulted in a 15% decrease in tensile strength compared with the as-built components [ 13 ].…”

“…Růžičková et al explored the concept of intermediate temperature stress relief treatments to map the response of SLM-fabricated AlSi10Mg to different heat treatment factors [ 13 ]. The authors determined that heat treatment at 240 °C for 2/6 h followed by a furnace cool to 100 °C and air cooling resulted in a 15% decrease in tensile strength compared with the as-built components [ 13 ]. It was also noted that hold time at 240 °C cases did not significantly impact the tensile properties [ 13 ].…”

“…The authors determined that heat treatment at 240 °C for 2/6 h followed by a furnace cool to 100 °C and air cooling resulted in a 15% decrease in tensile strength compared with the as-built components [ 13 ]. It was also noted that hold time at 240 °C cases did not significantly impact the tensile properties [ 13 ]. In contrast, treatment at 300 °C for 2 h followed by water quenching/air cooling resulted in greater degradation of the tensile strength [ 13 ].…”

“…It was also noted that hold time at 240 °C cases did not significantly impact the tensile properties [ 13 ]. In contrast, treatment at 300 °C for 2 h followed by water quenching/air cooling resulted in greater degradation of the tensile strength [ 13 ]. Mfusi et al explored the use of a 300 °C/2 h stress relief treatment on SLM AlSi10Mg and also noted a dramatic decrease in the tensile strengths (UTS: 420–470 MPa as-built/110–160 MPa after stress relief) and an improvement in the ductility [ 14 ].…”