Interface Characterization of Ni/Al Bimetallic Explosively Welded Plate Manufactured with Application of Exceptionally High Detonation Speed

Abstract

The investigation is dedicated to the detailed microstructure characterization of explosively welded clads, in which, exceptionally and for cognitive purposes, a very high detonation speed of about 2800 m/s was used to manufacture bimetallic aluminum-nickel plates. The study involves detailed microstructural characteristics of the bonded zone at micro and nano level, especially focused on the expanded melted regions consisted mostly of Al3Ni, Al3Ni2 and AlNi phases. In situ heating experiment in transmission electron microscope allowed observing microstructure transformation revealing that additionally present metastable Al9Ni2 phase was transformed to Al3Ni and Al3Ni2. Microhardness measurements across the welded zone showed the increase of the microhardness of nickel alloy plate from 153 up to 170 HV when approaching to the Ni201/A1050 interface, while the value for aluminum plate was of 45 HV. Within the melted zones the microhardness was found to be 135 HV and it enormously increased to 850 HV after annealing of the sample at 500 °C. This change was due to the transformation of the interface region from the waves with the melted zones into the continuous layers of two intermetallic phases: Al3Ni and Al3Ni2. The second phase grew at the expense of the Al3Ni.

On the Disintegration of A1050/Ni201 Explosively Welded Clads Induced by Long-Term Annealing

“…The applied detonation velocity of 2000 m/s was high enough to obtain continuous weld between Al and Ni plates ( Figure 3 a), the same as in the case of very high detonation velocity of 2800 m/s, reported previously in [ 40 ]. In both these cases, the asymmetric waves at the interface are observed.…”

“…Paul et al [ 11 ] have shown a series of microstructure images of Ti/Cu explosive welds, manufactured with the application of different V d in the range of 2000–3000 m/s and SOD increasing gradually by 1.5 mm in the range of 1.5–9.0 mm, where this relationship can be directly followed. Results presented here and in [ 40 ] show that the increase of V d and SOD causes an increase of waves’ amplitude and distance between their crests as in [ 11 ]. Guo et al [ 27 ] studied Ni/Al/Ni sandwiches manufactured by EXW with the detonation velocity of about 2100 m/s, indicating that the melted regions are more pronounced when the SOD is higher.…”

“…The thickness of the interface was defined as the average height of waves measured as a distance between the highest point at the crest of the wave to the base line indicating the place where the wave began to form. The interface of E2000 presented in Figure 3 a consists of melted areas along the whole length of the bonding zone, and it is flatter in comparison to the E2800 ( Figure 4 in current work and Figure 2 a in [ 40 ]), where the obvious wavy morphology prevailed. Such difference in the appearance of interfaces may result from few factors.…”

“…Detailed microstructural observations carried out in this study for both E2000 and E2800 ( Figure 3 b–d and Figure 4 a–d) revealed typical rapidly solidified microstructure, particularly expressed by fine dendritic microstructure with visible core and arms. As it is presented in [ 40 ], in the case of E2800, the average size of primary arms of the dendrites was about 480 nm (range of 250 to 670 nm), and secondary arms reached an average length of 240 nm (range of 150 to 350 nm). Reduction of detonation velocity to 2000 m/s resulted in the presence of dendrites with the mean size of primary arms of about 280 nm (being in the range of 230 to 400 nm), while the precise determination of secondary arms size was impossible based on the SEM images.…”

“…Explosive welding set-up prepared to manufacture Ni/Al clad with lower detonation velocity (V d ) of 2000 m/s was composed of Al acting as a flyer plate accelerated toward the Ni base plate located with the stand-off distance denoted as 2h ( Figure 1 a). In the second case, represented in Figure 1 b, the applied detonation velocity of 2800 m/s was exceptionally high [ 40 ]. In such case, the nickel alloy was applied as a flyer plate and aluminum alloy as a base plate with a shorter distance between the plates of 1h ( Figure 1 b).…”