Microstructure and mechanical property characterisation of aluminium–steel joints fabricated using ultrasonic additive manufacturing

Abstract

Driven by the interest to weld steel and aluminium (Al) in the solid state to prevent intermetallic formation, 9 kW ultrasonic additive manufacturing (UAM) has been used to fabricate Al 6061-4130 steel dissimilar metal builds. In addition, Al 6061-6061 builds were fabricated using similar techniques to provide a baseline for mechanical property measurement. Mechanical testing performed using pushpin testing shows that steel-Al dissimilar metal welds fail across multiple layers while Al-Al welds delaminate from the substrate. Multi-scale characterisation indicates that the change in failure morphology is due to the formation of metallurgical bonds in the Al-steel builds. Texture analysis shows identical textures at the interface of Al-steel, Al-Al and Al-Ti joints; showing that the bond formation in all cases relies extensively on plastic deformation across multiple materials. In addition, no changes to the bonding mechanism occurred when the materials used as foils and substrate were swapped.

Power Ultrasonic Additive Manufacturing: Process Parameters, Microstructure, and Mechanical Properties

“…As expected, the resulting microstructure and mechanical properties would be affected by the UAM process parameters. For this reason, a significant part of the literature on UAM paid more attention to optimization of the process parameters [29,34,40,44] and microstructural analyses [12,22,28,45,46] of the as-built part. e microstructural analyses provide substantial information about the bonding mechanism, grain refinement, and defects, which are highlighted in the next section.…”

“…Higher load and larger area under the curve correspond to better push-pin performance. Sridharan et al [22] reported the push-pin testing performance of Al6061-T6 foils on annealed 4130 steel (Al6061-4130) and Al-Al (Al6061-6061) builds. is was attributed to the high plastic flow at the interface resulting in oxide removal and asperity collapse, improving the metallurgical bonds and the mechanical properties.…”

“…While studies of fatigue life of additive manufactured parts have been widely reported for other AM techniques [62][63][64][65][66][67][68][69][70], there are still no adequate and substantial reports on the fatigue life performance of UAM parts. Most of the UAM reports have concentrated on optimizing processing parameters [14,29,34,40,44], microstructure [12,22,28,41,45,46], interfacial bonding shear [17,48] and tensile strength [13][14][15], and hardness [10,12,16,20,27]. Moreover, tests such as tensile and shear strength might provide more adequate indication/ information of the properties at the interface than fatigue testing.…”

“…For instance, UAM has shown great potential in fabricating metallic and metal-matrix composite parts, but the process has been limited by a lack of wide range of applications such as high-temperature applications. Significant efforts [12,17,22,28,45,46,48] have been made to understand the interface characteristics. However, eliminating interfacial defects is still a challenge encountered in UAM builds even though posttreatments have shown promising results.…”

“…With this attribute, bonding of dissimilar materials becomes feasible, and the properties of each building martial are retained. Similar and dissimilar builds via UAM such as Al-Al [10,[12][13][14][15], Al-Ti [16], Al-NiTi [17], Al-SiC [18,19], Al with embedded dielectric materials (inks used in printed electronics industry) [20], low carbon steel [21,22], and Alshape memory alloy (SMA) [23] have been reported in the literature so far.…”