Kirkendall effect

The Kirkendall effect is the motion of the interface between two metals that occurs due to the difference in <a href="/facts/Diffusion/KbAxroBa">diffusion</a> rates of the metal atoms. The effect can be observed, for example, by placing insoluble markers at the interface between a pure <a href="/facts/Metal/PT8hNX6R">metal</a> and an <a href="/facts/Alloy/I7w7WQWR">alloy</a> containing that metal, and heating to a temperature where <a href="/facts/Atomic_diffusion/kNtG3tVA">atomic diffusion</a> is reasonable for the given timescale; the boundary will move relative to the markers.
This process was named after <a href="/facts/Ernest_Kirkendall/WBWk2jMv">Ernest Kirkendall</a> (1914–2005), assistant professor of <a href="/facts/Chemical_engineering/Fb64amQf">chemical engineering</a> at <a href="/facts/Wayne_State_University/DI8huwcr">Wayne State University</a> from 1941 to 1946. The paper describing the discovery of the effect was published in 1947.
The Kirkendall effect has important practical consequences. One of these is the prevention or suppression of voids formed at the boundary interface in various kinds of alloy-to-metal bonding. These are referred to as Kirkendall voids.

Kirkendall effect open-in-new

Kirkendall effect