2. Fourier transforms

2.1 Experimental approach

At the end of the 19th century, a German metallurgist by the name of Wilm took a keen interest in aluminum, whose production process had just been perfected. The applications for this easy-to-form metal were potentially numerous, but its poor mechanical qualities were a lock. Wilm therefore sought to reproduce what was known about steel, an Fe-C alloy whose hardness rises sharply following rapid cooling, or quenching: a metastable phase, martensite, generated during quenching was responsible for hardening. He therefore tried to reproduce this phenomenon on an Al-Cu alloy (a few percent by mass of copper), alas without success, and it was only after annealing the quenched alloy at moderate temperature that the hardening phenomenon was observed, giving then...