*Article* **Multipass Friction Stir Processing of Laser-Powder Bed Fusion AlSi10Mg: Microstructure and Mechanical Properties**

**Akbar Heidarzadeh 1,\*, Mahsa Khorshidi 1, Roghayeh Mohammadzadeh 1, Rasoul Khajeh 2, Mohammadreza Mofarrehi 3, Mousa Javidani <sup>3</sup> and X.-Grant Chen 3,\***


**Abstract:** The effect of multipass friction stir processing (FSP) on the microstructure and mechanical properties of an AlSi10Mg alloy produced by laser-powder bed fusion was investigated. FSP was performed at a rotational speed of 950 rpm and traverse speed of 85 mm/min. The results indicated that FSP destroyed the coarse grain structure in the as-built AlSi10Mg by generating fine and equiaxed grain structures with shear texture components of *A*∗ <sup>1</sup> (111) 112 and *A*∗ <sup>2</sup> (111) 112 , in addition to causing fragmentation and refinement of the Si networks. FSP reduced the tensile strength slightly but significantly improved ductility. One-pass FSP exhibited superior mechanical properties compared with the two- and three-pass scenarios. The higher strength of the one-pass sample was attributed to the strengthening mechanisms induced by the Si particles, which were grown by repeated FSP. The higher ductility of the one-pass sample was explained using the kernel and grain average misorientations. Furthermore, the post-FSP microstructural evolution and fracture behavior of the samples were discussed.

**Keywords:** AlSi10Mg alloy; laser-powder bed fusion; friction stir processing; microstructure; mechanical properties
