**The E** ff**ect of Stress Relief on the Mechanical and Fatigue Properties of Additively Manufactured AlSi10Mg Parts**

#### **Busisiwe J. Mfusi 1,2,\*, Ntombizodwa R. Mathe 2,\*, Lerato C. Tshabalala 2 and Patricia AI. Popoola 1**


Received: 25 July 2019; Accepted: 14 October 2019; Published: 12 November 2019

**Abstract:** The heating and cooling profiles experienced during laser additive manufacturing results in residual stresses build up in the component. Therefore, it is necessary to perform post build stress relieving towards the retention and improvement of the mechanical properties. However the thermal treatments for conventional manufacturing do not seem to completely accommodate these rapid heating and cooling cycles of laser processing techniques such as powder bed fusion. Characterizations such as density measurements on the samples were performed employing the Archimedes principle; hardness testing was performed on the Zwick micro/macro (Hv) hardness tester, SEM and Electron backscatter di ffraction (EBSD). Fracture toughness and crack growth was conducted on a fatigue crack machine. All characterization was done after stress relieving of Selective Laser Melting (SLM) produced samples at 300 ◦C for 2 hrs was performed in a furnace. The mechanical properties appear to be rather compromised instead of being enhanced desirably. As-built SLM produced tensile specimens built in di fferent directions exhibited significantly favorable mechanical properties. However, post stress relieve thermal treatment technique deteriorated the strength while increasing the ductility significantly. Nonetheless, fatigue crack growth and fracture toughness illustrated positive outcome in terms of fatigue life on SLM produced AlSi10Mg components in application.

**Keywords:** selective laser melting (SLM); Alsi10Mg; stress relieve; additive manufacturing
