Whilst working in military research centre in Neubabelsberg in 1901, Wilm discovered age hardening, in particular age hardening of aluminium alloys. This discovery was made after hardness measurements on Al-Cu alloy specimens were serendipitously found to increase in hardness at room temperature. This increase in hardness was identified after his measurements were interrupted by a weekend, and when resumed on the Monday the hardness had increased.
By 1906, Wilm had developed an alloy – Al-3.5–5.5%Cu-Mg-Mn, Mg and Mn were < 1%, for which a patent was filed. Later this patent was purchased and the alloy marketed as duralinium. Somewhat unusually Wilm did not write his first article on age hardening until 1911. At the time Wilm was developing an aluminium alloy to replace brass in ammunition. The patent on duralumium was ignored and breached by a many firms and he struggled without success to protect his rights under it.
- Hardouin Duparc, Olivier (March 28, 2005). "Alfred Wilm and the beginnings of Duralumin". Zeitschrift für Metallkunde. Zeitschrift für Metallkund 96 (4): 398–404. ISSN 0044-3093.
- Hornbogen, Erhard (May 2001). "Hundred years of precipitation hardening". Journal of Light Metals (Elsevier Science) 1 (2): 127–132. doi:10.1016/S1471-5317(01)00006-2.
- Polmear, Ian (2006). Light Alloys: From traditional Alloys to Nanocrystals, 4th edition. Elsevier. ISBN 0-7506-6371-5.
- DE 244554 Verfahren zum Veredeln von magnesiumhaltigen Aluminiumlegierungen. (German patent) 20 March 1909.
- Wilm, Alfred (April 22, 1911). "Physikalisch-metallurgische Untersuchungen über magnesiumhaltige Aluminiumlegierungen". Metallurgie : Zeitschrift für de gesamte Hüttenkunde 8 (8): 225–227. ISSN 1011-4599.
- Saalberg, now known as Zachełmie, is a district in the municipality of Podgórzyn (Giersdorf). Before 1945 it was in south eastern Germany.
- Walther Pahl, Weltkampf um Rohstoffe. Leipzig 1941, S. 126.