Kirkendall void creation

Sometimes interdiffusion between two metals is uneven and may lead to the creation of vacancies or voids. This type of imbalance is the result of possible unequal mobilities between a metal couple. These voids occur individually near the common interface. The voids, like bubbles, coalesce, resulting in porosity and loss of strength. Many thin-fihn couples exhibit this phenomenon, which is referred to as Kirkendall void creation. Al-Au, Cu-Pt, and Cu-Au are just a few examples. To be specific, it has been found (7), for instance, that in the case of Au-Ni, about five times more Ni atoms diffuse into Au than Au atoms diffuse into Ni. 

Kirkendall void formation can, however, be prevented from occurring by choosing the right metal species. For example, whereas platinum coating on copper is subject to the Kirkendall void creation process, the same coating on electrodeposited nickel is free of it even if heated to as high as 600°C for many hours (more than 10 hours ). 

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See also in sourсe #XX -- [ , ]

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