In-situ investigation of interlayer interface bonding defect-formation mechanisms during FRAM

Abstract

The formation mechanisms of interlayer interface defects in friction-rolling additive manufacturing are yet to be investigated systematically. This study employs the emergency-stop technique, in-situ measurements, and metallographic characterization to investigate the interface morphology, transient temperature, and deposition forces in the action zone during the deposition, thereby revealing the formation mechanisms of interlayer interface defects and the flow behavior of materials. The findings indicate that at n = 1400 rpm, the action zone (TC2) temperature measured in situ is 543.6°C, with average transverse force (Fx) and downward force (Fz) values of 210 and 270 N, respectively. When v = 180 mm/min, the TC2 temperature is 493.6°C, with Fx and Fz values of -700 and 1900 N, respectively. The shorter dwell time reduces the material’s plastic deformation and flow, thus resulting in insufficient material flow. When h = 1.2 mm, the TC2 temperature is 452.3°C, with Fx and Fz values of -748 and 404 N, respectively. The interface material is not effectively stirred by the toolhead, which hinders sufficient plastic flow, thus resulting in the lowest bonding quality. The formation of defects is attributed to significant differences in the TC2 temperature and Fz, which diminish the toolhead’s stirring and rolling effects. Although an increase in the deposition layers increases the TC2 temperature, interface defects remain incompletely suppressed, ultimately affecting the mechanical properties of the samples. This study elucidates the significance of in-situ temperature and Fz measurements, thus providing a theoretical foundation for further efforts to suppress interfacial defects.