A comparative investigation on the microstructure and mechanical properties of additively manufactured aluminum alloys

• Published in: International journal of fatigue 2021-05, Vol.146, p.106165, Article 106165
• Main Authors: Muhammad, Muztahid, Nezhadfar, P.D., Thompson, Spencer, Saharan, Ankit, Phan, Nam, Shamsaei, Nima
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Aluminum; Aluminum base alloys; Crack initiation; Crack propagation; Fatigue; Fatigue failure; Fatigue strength; Fatigue tests; Fracture mechanics; Laser beam powder bed fusion (LB-PBF); Laser beams; Materials fatigue; Mechanical properties; Microstructure; Notches; Powder beds; Precipitates; Room temperature; Stiffness; Strain rate; Tensile properties; Tensile tests; Ultrafines
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2021.106165

[Display omitted] •Mechanical properties of additively manufactured (AM) Al alloys are investigated.•Chemical composition & stress relief scheme affect the microstructure of AlSi10Mg.•Scalmalloy has high strength and ductility due to its nano-size microstructure.•Scalmalloy exhibits superior fatigue resistance among the Al alloys investigated.•Surface notches and volumetric defects are the major crack initiation sources. Due to exceptional strength/stiffness to weight ratio, aluminum (Al) alloys are being extensively used in many exclusive applications. The microstructure, and consequently, the mechanical properties of additively manufactured (AM) Al alloys are expected to vary compared to those of their conventionally manufactured counterparts due to the unique thermal history experienced during the additive manufacturing (AM) processes. Therefore, it is critical to understand the microstructure and characterize the mechanical properties of AM Al alloys to verify if they meet the requirements for being deployed in the fatigue critical applications. In this study, the microstructure and mechanical properties (i.e., tensile and fatigue) of laser beam powder bed fused (LB-PBF) LPW AlSi10Mg, EOS AlSi10Mg, Scalmalloy, and QuesTek Al alloys are characterized. Room temperature quasi-static tensile tests are conducted at the strain rate of 0.001 s−1 on machined surface specimens, and uniaxial fully-reversed strain-controlled fatigue tests are performed on both as-built and machined surface specimens. Some differences in microstructure and tensile properties of the LB-PBF AlSi10Mg fabricated with LPW and EOS powders are noticeable. Among the Al alloys, the LB-PBF Scalmalloy possesses the highest strength and high ductility as well as the highest fatigue resistance credited to its ultrafine/nano-size grains and precipitates. For all the LB-PBF Al alloys investigated, surface micro-notches and volumetric defects (pores, lack of fusion) are found to be the primary sources of fatigue crack initiation in the as-built and machined surface conditions, respectively.