Alfred Wilm (25 June 1869 – 6 August 1937) was a German metallurgist who invented the alloy Al-3.5–5.5%Cu-Mg-Mn, now known as Duralumin which is used extensively in aircraft. Whilst working in military research NUTZ 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 they were resumed on the Monday the hardness had increased.