Microstructure of Bonding Interface in Explosively-Welded Clads and Bonding Mechanism

Abstract

Microstructural aspects and bonding characteristics of the explosive welded Ti/Ti, Ti/steel and Ti/Ni clads were investigated mainly by TEM microscopy. It was found that the bonding interface was composed of layers of metastable phases such as amorphous phases, icosahedral quasicrystal and intermetallic compounds. These metastable phases are formed as a trace of melting followed by subsequent rapid solidification of thin layers of about 200 nm in thickness along the contact surface of both the component materials.It is concluded that the very thin melting layer is responsible for the bonding of explosively welded Ti base clads and especially amorphous phase formed in the bonding interface keeps high bonding strength.

The Effect of Anvil Geometry and Welding Energy on Microstructures in Ultrasonic Spot Welds of AA6111-T4

“…[21][22][23][24][25][26][27][28][29] Explosive welding involves the initial melting and ejection of surface, followed by the formation of straight sections and vortices alternating along the wavy interface. Either crystalline phases or isocahedral/amorphous phases [30] can be found at the straight sections of bonding, and resolidified microstructures [31,32,33] attributable to additional adiabatic heating and melting are identified at the vortex cores. In contrast, the wakes in ultrasonic welds occur in the absence of any microstructural evidence of melting at micrometer scale.…”

Explosively welded multilayer Ni–Al composites

“…At the same time, the deformation at a high strain rate, elevated pressure at the contact point, and short duration of the explosive welding process may result in unique and uncommon structures at the interface between welded materials. Nishida et al [13,14] and Chiba et al [15] observed the formation of amorphous and quasicrystalline phases in explosively welded Ni-Ti bimetals. In addition, they found amorphous structures in explosively welded Ti-steel bimetals.…”

TEM Observations of the Microstructural Changes in the Interfacial Zone of Explosively Welded Titanium/Steel Before and After Ex Situ and In Situ Heat Treatment

“…Such a layer can only be observed using transmission electron microscopy (TEM). In general, it has been found that the thickness of the observed layer is in the range of 100–300 nm (Chiba et al, 2004; Song et al, 2011; Paul et al, 2014; Guoyin et al, 2017) or thicker (Gloc et al, 2016; Wachowski et al, 2017; Lazurenko et al, 2018), depending on the location of the extracted TEM lamella (Chu et al, 2019). This thin interlayer has an amorphous or fine crystalline structure (Chiba et al, 2004; Yang et al, 2006; Chu et al, 2017; Guoyin et al, 2017; Lazurenko et al, 2018).…”

“…In general, it has been found that the thickness of the observed layer is in the range of 100–300 nm (Chiba et al, 2004; Song et al, 2011; Paul et al, 2014; Guoyin et al, 2017) or thicker (Gloc et al, 2016; Wachowski et al, 2017; Lazurenko et al, 2018), depending on the location of the extracted TEM lamella (Chu et al, 2019). This thin interlayer has an amorphous or fine crystalline structure (Chiba et al, 2004; Yang et al, 2006; Chu et al, 2017; Guoyin et al, 2017; Lazurenko et al, 2018). There are, however, some works on explosively welded titanium/steel joint using TEM (Song et al, 2011; Guoyin et al, 2017; Wachowski et al, 2017), where some discrepancies have been found in the description of the microstructure of the interface zone.…”