Growth rate of intermetallic compounds in Al/Cu bimetal produced by cold roll welding process

Above 120 °C, intermetallic compounds can occur between aluminum and copper, and these compounds often have low strength, brittleness, and high electrical resistance.

“Above 120 °C, intermetallic compounds can occur between aluminum and copper, and these compounds often have low strength, brittleness, and high electrical resistance [32].”

Abbasi et al. described a change in fracture behavior from ductile to brittle after the thickness of the intermetallic phases reached 2.5 μm.

“Abbasi et al. [6] described a change in fracture behavior from ductile to brittle after the thickness of the intermetallic phases reached 2.5 µm.”

Abbasi et al. describe a critical phase thickness of 2.5 μm for the cold roll welding process, above which the compound strength decreases drastically and the fatigue behavior changes from elastic to brittle.

“Abbasi et al. [6] further describe a critical phase thickness of 2.5 µm in their investigations for the cold roll welding process.Above this critical phase thickness, the compound strength decreases drastically and the fatigue behavior changes from elastic to brittle.”

Some studies show that excessively high growth in the intermetallic phase thickness leads to a reduction in compound strength.

“However, some studies show that excessively high growth in the intermetallic phase thickness, in turn, leads to a reduction in compound strength.”

Previous studies have demonstrated that Al-Cu bimetallic welds have high resistance that can increase further from relatively short term exposure to temperatures above 150°C.

“Previous studies have demonstrated that Al-Cu bimetallic welds have high resistance that can increase further from relatively short term exposure to temperatures above 150 • C [11,12].”

Most studies have not performed heat treatment ageing and the relative resistance increase metric was only identified in a few studies.

“As such, most studies have not performed heat treatment ageing and this metric was only identified in a few studies [11,12].”

Several studies did not specify if bulk conductivity was measured, and in a few studies it was not measured or reported.

“Several studies did not specify if bulk conductivity was measured [11,12,28], and in a few studies it was not measured [30], or reported [13].”

The activation energy and pre-exponential constant for aluminum and copper interfaces have been reported for several processes.

“The activation energy and pre-exponential constant for aluminum and copper interfaces have been reported for several processes [11][12][13][14][15][16][17][18][19][20][21][42][43][44][45][46].”

A widely used criterion for the integrity of Al-Cu welds is maintaining a total thickness of intermetallic compounds below 2 μm.

“A widely used criterion for the integrity of Al-Cu welds is maintaining a total thickness of intermetallic compounds below 2 μm [11,12,31,40,47,48].”

Chemical cleaning processes such as washing and degreasing are typically used to remove contaminant layers.

“This is typically achieved through chemical cleaning processes such as washing and degreasing [8].”

Above 250 °C, the growth of intermetallic compounds accelerates distinctly.

“Above 250 °C, the growth of IMC accelerates distinctly [8].”

Cold roll bonding followed by additional annealing is common to improve interface strength.

“Therefore, cold roll bonding followed by an additional annealing is common to improve the interface strength [8,10,11,5].”