Which preposition to use with metallurgy

of Occurrences 5%

The texture of the inner portions of these foreign anodes would lead one to infer that the metallurgy of nickel was very primitive.

at Occurrences 1%

The first officer's cabin is occupied by Professor Titus Peebles, M.R.C.S., M.R.G.S., lately instructor in metallurgy at the University of Edinburgh, and Mr. William Beauvoir.

Which preposition to use with  metallurgy