Alfred Wilm and the hardening of metals

The pseudo-history of science is full of that old trope of ‘the accidental discovery’. It makes for great, romantic story-telling, and excellent click-bait. Archimedes, we all know, ran stark naked, bellowing ‘Eureka’, down the streets of Syracuse while thinking about density. We also have Hennig Brandt distilling urine and obtaining white phosphorus. Ira Remsen’s saccharin-contaminated bread. Alexander Fleming’s mould. The list goes on.

But are they really accidents? The word accident is a banana skin word with a slippery meaning. At first hearing it evokes the idea of something random, a bolt from the blue event that cannot be explained by rational thought.

Yet creativity and discovery in science can never be an accident. Ideas are anything but random; they only take place with the right preparation, something that historians of science have argued for a very long time. After all, it is only if you know what you expect that the unexpected can have a chance of attracting your attention. But even then, you might still dismiss it as a ‘failure’ and let it go.

Precipitating discovery

The discovery of age or precipitation hardening in metals, a phenomenon that I have relied on over the years as a cyclist, is one example that is often termed an ‘accidental’ discovery. The man who spotted it was Alfred Wilm, who was born in 1868 into a wealthy family in Silesia in the rolling hills of what is today South Eastern Poland, but was then part of the German-speaking nation-state unified by Bismarck. His father was a minor aristocrat while his mother, Olga, was the daughter of the prominent Berlin jeweller Hermann Julius Wilm, whose father and grandfather had created jewels for Napoleon and Frederick the Great respectively. Metals were therefore, in a sense, in the family.

Wilm was one of 13 siblings. The children were first educated, as was the fashion, by governesses. As a teenager he attended the high school in nearby Leignitz (Legnica). His interest in chemistry seems to have led him to study at the Royal Technical School in Breslau (Wrocław). There is no sign, however, that he ever received a degree.

In 1886 he moved to Berlin where he got a position as a research assistant at the Technical University to Julius Franz Weeren in Charlottenburg, a specialist in the smelting of metals – this gave him his first taste for metallurgy. He did internships at the Royal Foundry in Gleiwitz, followed by time in Kassel where he helped develop methods to separate the alkaline earths. In 1893 he became a research assistant to Richard Lorenz in Göttingen, a young physical chemist. When Lorenz ‘received the call’ to a professorship at ETH in Zürich, Wilm moved yet again, this time spending a year in Düsseldorf where Carl Hohmann was setting up a metallurgy laboratory. It is possible that many of these positions were unpaid; he may have been supported by his parents.

In March 1897 he found a job at Karl Goldschmidt’s chemical works in Essen. Goldschmidt is remembered today for the thermite reaction, the aluminothermic smelting of iron that he turned into a method for creating continuously welded rails. The reaction was later unleashed in incendiary weapons that torched British and German cities in the second world war, including Essen itself. Initially appointed as head of the research laboratory, Wilm soon shifted to the smelting division. He would stay for four years and must have built something of a reputation for himself.

In 1901, he was recruited by Richard Stribeck, a tribologist who was building up a new government-funded ‘Centre for Technical and Scientific Research’ in the Berlin suburb of Neubabelsberg. The institute was part of the German military-industrial complex and its focus was on science for the defence sector.

Hard work

The challenge that was set before Wilm in 1902 was to find an alloy of aluminium that was strong and hard enough for use by the military, as a lighter alternative to steel. As a structural material, aluminium was a bust. Aluminium spoons and canteens, let alone airframes or carriages were annoyingly weak and bendy. Lighter equipment would be a game changer for logistics and weaponry – and for those dreaming of flight. Much as tin can be stiffened by the addition of copper to make bronze, the idea was to identify a composition that would fit the bill.

According to one legend, one Saturday morning in 1906 Wilm added half a percent of magnesium to a batch of Al-Cu-Mn alloy. After rolling the metal into a sheet and annealing it in a molten salt bath, Wilm asked Jablonski to test the hardness. His collaborator demurred, citing a lunchtime meeting. When Wilm pressed him, Jablonski reluctantly made a quick measurement; yes, the alloy was harder, but Jablonski was late so he hurried away. On the Monday he repeated the measurement with Wilm looking over his shoulder. To their surprise the metal was seriously hard. The result was so striking that Wilm asked Musehold whether anyone had messed with the instrument over the weekend.

Wilm and Jablonski repeated the process. Sure enough, the metal changed radically over a few hours, yielding a proper engineering material. Further experiments showed that hardening by heating and aging sometimes worked for alloys, but never in pure materials. If its origin was a mystery, the discovery was obviously worth something. In 1909 Wilm filed a patent focused on the method of age hardening.

The same year, his boss Richard Stribeck was poached by the great steelmaker Krupp to lead their metallurgy research and Wilm found himself with a different boss with different priorities. Wilm quit, taking his patent with him. He licensed it to a foundry in the town of Düren in Westphalia, the industrial heartland of Germany. The company began to market the new metal under the name Duralumin (a half-pun implying ‘dur’, hardness, and ‘dür’, Düren) as a replacement for wood, magnesium, and even some carbon steels for Zeppelins.

Losing control

One of the first customers was the Vickers foundry and engineering business in Sheffield, UK, which had been commissioned to build an airship. The resulting airship ‘Mayfly’ broke up before its first flight. While ‘foreign alloys’ were publicly blamed for this disaster, it was ultimately caused by design flaws.

Vickers bought the rights to Duralumin and began to conduct alloy research of their own; their analyses led them to realise that an additional impurity – silicon – was critical to the change in properties, something they kept very quiet about. Vickers licensed the rights to a French firm that also began manufacturing the material.

Wilm sensed that he was losing control of ‘his’ material, especially after Vickers started saying that their chief metallurgist Henry Weeks was the real inventor. Wilm published articles about the material and its properties to establish priority. He also began an expensive series of lawsuits to try to assert his rights, all of which came to nothing.

Eventually, after the first world war, he gave up. He sold his house in Berlin and with the proceeds bought a farm with his second wife in the village of Saalberg im Riesenberg (Zachełmie), in the picturesque mountains of Silesia. He started a chicken farming and breeding business, styling himself Ing-Dr. honoris causa. His science days were not quite over, however. He seems to have worked as a consultant to the Diamant Fahrradwerke, in Chemnitz, Saxony, whose aluminium alloy frames would later become legendary. And Wilm was clearly never forgotten because when he died in 1937, his funeral included a fly-past led by one of Nazi Germany’s leading woman pilots in Duralumin aircraft.

Wilm never found out the reasons for the magical hardening he had discovered. X-ray diffraction and methodical microscopy showed that minor components of an alloy migrated and reacted forming intermetallic microcrystals – in Wilm’s case Mg₂Si and CuAl₂ – which interfere with the movement of dislocations moving through the metal. Precipitation hardening is a central tool in the arsenal of the metallurgist; myriad aluminium alloys treated in endless proprietary heating and cooling protocols provide the backbone of the aerospace industry, smooth rides for cyclists, and even the casings of our computers.

And yet all this leaves unanswered the question of what predisposes an individual to act on something odd. Can it be taught? Perhaps, but Wilm’s example shows that paper qualifications are no advantage. There are some things that will forever be mysterious, although one can be sure that they are not accidents.

Acknowledgement

Julian Evans made me fall in love with metals and their strangeness. Thank you! I still have your book.