Effects of Build Interruption and Restart Procedure on Microstructure and Mechanical Properties of Laser Powder Bed Fusion Al-Si-10Mg

Additive manufacturing (AM) requires a significant capital investment to acquire a machine, procure raw material, and train operators to begin production. This substantial overhead means interruptions to the AM build process can become a costly event if the interruption results in significantly reduced build quality. Interruptions in the form of power outages, lack of powder feedstock, and/or loss of shielding gas can cause the machine to operate in an unintended manner, interrupting the build and potentially even stopping the entire process. An interrupted laser powder bed fusion process could result in reduced mechanical properties, localized failures, and physical characteristics that distinguish an interrupted component from a continuous one. This investigation aims to explore the effect of various build interruption conditions (i.e., duration of the interruption and air exposure) on microstructural and mechanical properties of Al-Si-10Mg fabricated via a laser powder bed fusion (LPBF) system. Seven builds were completed for this study, a control along with six interruption experiments with three distinct time lengths for the interruption periods: 15 min, 12 and 24 h. Each interruption period was repeated to explore the effects of air exposure during the stoppage. The effects of interruptions were characterized by x-ray computed tomography, optical microscopy, scanning electron microscopy, Vickers microhardness, and destructive oxide testing. Strain rate-controlled tension tests were conducted to determine mechanical properties. Results indicated no reduction in mechanical properties (i.e., tensile and micro-hardness) for any of the interrupted specimens when compared to the control and literature on LPBF-processed Al-Si-10Mg. However, the 24-h group specimens experienced the most failures near the interruption location, indicating that failure location can be influenced by prolonged stoppage and air exposure.