Microstructural origin of high strength and high strain hardening capability of a laser powder bed fused AlSi10Mg alloy

• Published in: Journal of materials science & technology Vol. 197; pp. 194 - 206
• Main Authors: Li, C., Zhang, W.X., Yang, H.O., Wan, J., Huang, X.X., Chen, Y.Z.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 20-10-2024
• Subjects: AlSi10Mg alloy; Laser powder bed fusion; Plastic deformation; Strengthening mechanism; Laser powder bed fusion; Plastic deformation; AlSi10Mg alloy; Strengthening mechanism
• ISSN: 1005-0302; 1941-1162
• DOI: 10.1016/j.jmst.2024.01.067

•The stress and strain partitions of Al and Si phases have been measured.•The Al matrix contains the supersaturated solute Si.•The solute Si enhances yield strength and work hardening.•The cellular structure generates significant back stresses during deformation.•The deformation mechanism of alloys is closely reliant on cellular structure.
Compared to a cast AlSi10Mg alloy, a laser powder bed fused (LPBF) AlSi10Mg alloy shows superior yield strength and strain hardening capability. However, the underlying microstructure origin has not been comprehensively understood. In this work, the microstructural evolution of an LPBF AlSi10Mg alloy during tensile deformation was investigated. Synchrotron X-ray diffraction characterization shows that both stress and strain exhibit significant partition between an Al phase and a Si phase upon tensile deformation. This leads to a significant strain gradient between those two phases, which is evident by the high density of dislocations in the cell boundaries of the deformed alloy. The strain gradient results in long-range internal stress, also known as back stress, in the cell boundaries, and in turn leads to enhanced strength and strain hardening in the LPBF AlSi10Mg alloy. Quantitatively analyses via loading-unloading-reloading tests show that during the tensile deformation, the back stress contributes 135 MPa to the yield strength of the alloy, which continuously increases with increasing the strain beyond the yielding point. This work illuminates the microstructural origin of the back stress in the LPBF AlSi10Mg alloy, i.e. the back stress arises from the stress/strain partition between the Al and Si phases in the cellular structures, and the back stress leads to significant strengthening of the alloy upon tensile deformation. This work may also provide guidance for manipulating the mechanical properties of additively manufactured Al-Si alloys for specific application needs.
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