New discoveries in ultrasonic consolidation nano-structures using emerging analysis techniques

Abstract

This paper examines the influence of ultrasonic consolidation (UC) on the bonding interface and challenges existing opinion regarding the mechanism of oxide dispersal during UC bond formation. The findings presented in this paper were achieved through the use of dual beam focused ion beam (DBFIB) etching and transmission electron microscopy (TEM), enabling the close examination of the weld interface, sub-grain morphology, and dislocation structure in ultrasonically consolidated aluminium (Al) 3003-T0 samples.As a result of this investigation, it has been established that a persistent oxide layer between bonded foils often remains after UC with this material. The level of sub-grain refinement in ultrasonically consolidated components was seen to decrease as the distance from the weld interface increases. This trend was characterised by the nanoscale sub-grain and gradient subgrain regions, between which a distinct stepped transition was apparent. Direct contact with the sonotrode surface during the deposition of each new layer was also seen to cause significantly more sub-grain refinement than interface dynamics alone. Nano-grain colonies were also discovered in areas surrounding material flaws, manganese particles, or non-planar interface regions, and persistent dislocation slip bands were seen near the UC weld interface. In light of these results, the context of previously proposed methods of bond formation in UC is discussed.

A review of microstructure evolution during ultrasonic additive manufacturing

“…This early recrystallization and grain refinement is the first contribution to the microstructure and texture evolution at the welding interface. Grain refinement from the sonotrode had also been reported by Kuo et al [18] on the top of 4130 steel foil and by Johnson et al [68] on the top of Al 3003 O. Study from Dehoff and Babu [56] showed that the interaction between the sonotrode and the top surface of the foil during UAM process was very important for the following UAM process from two aspects.…”

“…Research from Johnson [44] also reported the grain refinement around the welding interface for Al 3003 O parts fabricated by ultrasonic consolidation. Johnson et al [68] demonstrated that the level of subgrain refinement in ultrasonically consolidated components was seen to decrease as the distance from the weld interface increased.…”

Power ultrasonics for additive manufacturing and consolidating of materials

“…The modified topology of the sonotrode is necessary to efficiently transfer kinetic energy to the bond interface during the oscillations and weld pressure and to induce sufficient plastic flow for bonding (Friel et al, 2010a;Johnson, 2008;Johnson et al, 2011;Li and Soar, 2009). The roughened surface creates a mechanical coupling and prevents energy loss through slippage (Weare et al, 1960).…”

“…Image reproduced courtesy of SAGE Publications(Johnson et al, 2011). Image reproduced courtesy of SAGE Publications(Johnson et al, 2011).…”

Laser-Machined Microchannel Effect on Microstructure and Oxide Formation of an Ultrasonically Processed Aluminum Alloy

“…How ever, high volumes of fibers may weaken the bond formation [7]. It has also been shown that the area in contact with the sonotrode exhibits grain refinement [6] which is restricted to a small area at the interface between the foils [5, 6,11]. To reduce the required amplitude and necessary matrix plastic flow, it was proposed to produce channels in UC samples to aid the placement and security during future fiber embedment via laser processing.…”