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The Kirkendall Effect

Have you ever wondered how atoms move inside a supposedly "solid" piece of metal?

In this video, we dive into the Kirkendall Effect, a groundbreaking discovery that proved atoms in solid metals migrate through "vacancy diffusion". Instead of atoms simply swapping places, they move by jumping into empty spaces—or vacancies—within the crystal lattice!

When two different metals are welded together, such as copper and nickel, they rarely diffuse into each other at the exact same rate. For instance, copper diffuses much faster into nickel than vice versa. This unequal flow of atoms leaves behind a net flow of vacancies in the opposite direction, which eventually clump together to form physical pores or voids within the solid metal.

https://www.phase-trans.msm.cam.ac.uk/kirkendall.html

Join us as we explore the simple but ingenious Kirkendall experiment that changed metallurgy forever, and discover how this phenomenon impacts modern technology, including:

Metallic Superconductors: How Kirkendall porosity appears during the heat treatment of niobium-tin (Nb3Sn) superconducting filaments.

Shape Memory Alloys: The clever manufacturing techniques used to roll and interdiffuse alternating layers of nickel and titanium, and the voids left behind.

Aerospace Superalloys: Why high-temperature turbine blades in jet engines must account for void formation between the blade and its protective nickel-aluminium coating.

Hot-Press Forming Steels: How extreme heating of coated high-strength steels causes interdiffusion between iron, silicon, and aluminium, resulting in Kirkendall voids.

Key Topics Covered: Vacancy Diffusion, The Kirkendall Experiment, Crystal Lattice Defects, Solid-State Diffusion, Metallurgy and Engineering

References: Based on "The Kirkendall Effect" by H. K. D. H. Bhadeshia.