In situ investigation into temperature evolution and heat generation during additive friction stir deposition: A comparative study of Cu and Al-Mg-Si

Additive friction stir deposition: a deformation processing route to metal additive manufacturing

“…As shown in Figure 4, infrared imaging from the side can be used to monitor the temperature evolution in the deposited material. Garcia et al [50] measured the peak temperature, exposure time, reheating rate, and cooling rate during AFSD of Al-Mg-Si and Cu under various conditions and found consistent physical trends. The peak temperature was found to be ∼ 50%-90% of the melting temperature, the exposure time is ∼ 10 1 s, the reheating rate is ∼ 10 1 -10 2 K/second, and the natural cooling rate is ∼ 10 1 K/second.…”

“…To compare, AFSD characteristically leads to refined, equiaxed microstructures due to its thermomechanical processing nature [35,36,49]. Because of the friction stir principle, the deposited material is severely and rapidly deformed with the peak temperature above half of the melting temperature [50]. This leads to dynamic microstructure evolution [51], which can be divided into discontinuous and continuous types of dynamic recrystallization depending on the characteristic physical variables in processing-e.g.…”

“…However, the precision of inplane dimensions relies on the material deformation and flow under the tool head. If the tool head drives sufficient material rotation, smooth edges arise along the deposition track, like the case in AFSD of AA6061 [50]. Otherwise, rough edges may form due to the 'flash' during material flow.…”

“…Compared to thermal monitoring, unraveling the material deformation history in AFSD is much more challenging given that the plastic deformation is rapid. While the work by Garcia et al [50] was able to provide the material deformation and flow information on the exterior surface, little was revealed internally. This is not useful to understand the deformation history of the deposited material, i.e.…”

“…The co-plastic deformation and mixing between the newly-deposited material and the layer underneath will lead to a diffuse interface with gradual changes in composition, microstructure, and phase fraction, rather than forming a sharp interface. Thanks to the short thermal cycle [50], there is a lower chance of forming undesired intermetallics at the interface. Even if brittle intermetallic phases form as a result of mechanical mixing, the imposed shear force and torque during AFSD would make them a globular shape with much less deterioration on the overall ductility [95,96].…”