Ultrasonic additive manufacturing of 4130 steel using Ni interlayers

Abstract

Ultrasonic additive manufacturing (UAM) is a solid-state manufacturing process for making complex components. However, fabrication of ferritic (body centered cubic) steels has been challenging for UAM due to its high hardness. This research successfully joined AISI 4130 steel sheets by using soft Ni (face centered cubic) interlayers. The localisation of plastic deformation in the Ni-interlayer leads to a significant reduction in voids. A post-process heat-treatment was designed using thermodynamic calculations to dissolve nickel into steel matrix. Energy dispersive X-ray spectroscopy measurements showed ∼ 10 µm Ni from the interlayer diffused into the steel side, confirming the feasibility of the approach. The shear tests show a higher shear strength in comparison to as-processed 4130 without interlayers and post processed using hot isostatic pressing (HIP).

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.…”

“…UAM is also capable of joining dissimilar or multiple materials, and it has been demonstrated in several researches [18,21,22,26,27,[48][49][50][51][52]. Obielodan [26] studied the feasibility of joining multi-materials, including Al, Ni, Ti, Ta, stainless steel, MetPreg, Ag, Mo and Cu, by UC, and the results showed that all FCC materials and some other material combinations could be bonded well by UC with a good LWD.…”

“…It is generally believed that it is easier to join a soft material to a harder material than to join a harder material to itself. This is why a softer interlayer can be used to improve the bonding between two harder material layers, as demonstrated by Kuo et al [18] using a Ni interlayer to join 4130 steel layers and by Wolcott et al [21] using an Al 1100 interlayer to join commercially pure Ti layers. This mechanism of using a soft interlayer to join hard materials has also been used for ultrasonic spot welding [53,54].…”

“…It was proved that strategy 2 was better than strategy 1 as to bonding density and joint quality. Janaki Ram et al [50] used strategy 1 and found out that a lot of defects formed between the harder layer and the previously as-deposited soft layer; however, Kuo et al [18] and Wolcott et al [21] found out that by using strategy 2, good welding density could be achieved at all interfaces. The influence of two indirect deposition strategies on the bonding density and joint quality can be explained below.…”

“…UAM has been used to fabricate soft materials, such as Al alloys [11,12], harder materials, such as copper [13][14][15], nickel [16], steel [17,18] and titanium [19][20][21], dissimilar materials, such as Al-Ti [21], Al-Cu [15], Al-steel [22], Al-NiTi [23,24], Al-MetPreg (a fibre-reinforced aluminium) [25][26][27] and Ni-steel [18] and metal matrix composite with embedded elements, such as SiC fibres [28,29], shape memory alloy fibres [30], dielectric materials (used in printed circuit board) [31], electronic circuitry [32], glass fibres and fibre optic sensors [33][34][35] and carbon fibres [36].…”