Laser impact welding application in joining aluminum to titanium

Abstract

Thin metal foil joining has wide applications in medical device and microelectronics. In this paper, laser impact welding was implemented to join aluminum foil to titanium sheet. The velocity of Al flyer was measured with photonic Doppler velocimetry. The maximum velocity reached up to 1000 m/s within 0.2 μs. Varied thickness (25–250 μm) Al flyer was successfully welded with Ti target. Weld strength was measured with peel test. Weld area was estimated with resistance measurement method. The effect of laser spot size, flyer thickness, standoff distance on weld strength, weld area, and microstructure was analyzed. The microstructure was studied with scanning electron microscopy (SEM). By comparing the amplitude and wavelength of the waves at the bonding interface, it is suggested that the wave formation was related to the impact velocity. SEM back scattered electron image did not show apparent diffusion across the weld interface. Both twinning and severe plastic deformation were observed at Ti side along the weld interface, which resulted in hardness increase in this region.

Investigation on a Novel Laser Impact Spot Welding

“…This result is the same with the finding presented by Wang's research for the welding of aluminum and titanium [19]. One way that this phenomenon could be explained as follows: At the initial phase of bonding between Ti and Cu, the bonding strength of the weld interface is relatively low due to the low collision angle (below 8˝) between the hump and base plate.…”

“…Springback can also be observed in the center of the weld spot as shown in Figure 4a; the area of the springback region increased when high pulse energy was used, as shown in Figure 4b. A similar phenomenon has been observed elsewhere [17,19]. The occurrence of the springback may be related to the effect of the reflected shockwave.…”

“…Normally, two morphologies can be achieved-flat and wavy [14,[16][17][18][19]-when the LIW has happened. Generally, a wavy weld interface is expected because this interface can increase the bonding area and assist interlocking between two metal surfaces [14] as shown in Figure 6b,d.…”

“…Similar to the aforementioned research, wave interfaces were also observed. More recently, Wang et al [18,19] reported the welding of Al/Ti with LIW and did not observe intermetallic phases in the weld interface. [16]; (b) parallel welding [17].…”

“…A new laser impact spot welding (LISW) approach is presented and applied to join thin titanium foil to copper foil with a low laser energy system. The morphology of the weld spots was Two basic geometric configurations of the LIW process have been reported, including angle welding [14,16] and parallel welding [17][18][19] as shown in Figure 1. However, in the angle welding process, the collision angle is constructed by means of an experimental device as shown in Figure 1a, which makes the clamping of the flyer plate and the base plate complicated.…”