TWO metallurgists at Stanford University, seeking to produce a ''superplastic'' metal, appear to have stumbled on the secret of Damascus steel, the legendary material used by numerous warriors of the past, including the Crusaders. Its formula had been lost for generations.
Analyses of steel by Jeffrey Wadsworth and Oleg D. Sherby, in their search for a highly plastic form, revealed properties almost identical to those they then found in Damascus steel, though their own plastic steel had been produced through contemporary methods.
The remarkable characteristics of Damascus steel became known to Europe when the Crusaders reached the Middle East, beginning in the 11th century. They discovered that swords of this metal could split a feather in midair, yet retain their edge through many a battle with the Saracens. The swords were easily recognized by a characteristic watery or ''damask'' pattern on their blades.
Through the ages - perhaps from the time of Alexander the Great in the fourth century B.C. -the armorers who made swords, shields and armor from such steel were rigidly secretive regarding their method. With the advent of firearms, the secret was lost and never fully rediscovered, despite the efforts of men like P.@P. Anossoff, the Russian metallurgist, who knew the steel as bulat.
In 1841 Anossoff declared: ''Our warriors will soon be armed with bulat blades, our agricultural laborers will till the soil with bulat plow shares. ... Bulat will supersede all steel now employed for the manufacture of articles of special sharpness and endurance.'' Yet his lifelong efforts to fulfill that dream were in vain.
Dr. Wadsworth and Dr. Sherby realized that they might be on the track of the method when a sword fancier, at one of their presentations, pointed out that Damascus steel, like their own product, was very rich in carbon. This led them to conduct comparative analyses of their steels and those of the ancient weapons.
Dr. Wadsworth, while still associated with Stanford, now works at the nearby Lockheed Palo Alto Research Laboratory. Dr. Sherby, a professor at Stanford, is an authority on deformable metals.
When moderately heated, superplastic steel can be shaped into such complex forms as gears for an automobile, with minimal need for machining, leading to major economies in manufacture. Their research, Dr. Wadsworth said recently, has shown how to make steel even more amenable to shaping than the Damascus variety.
A basic requirement, as suspected by a number of early metallurgists, is a very high carbon content. Dr. Wadsworth and Dr. Sherby believe it has to be from 1 to 2 percent, compared to only a fraction of 1 percent in ordinary steel. Another key element in Damascus blade produ ction seems to have beenforging and hammering at relatively low tempe rature - about 1,700 degrees Fahrenheit. After shaping, the blades were apparently reheated to about the same temperature, then rapidly cooled, as by quenching in a fluid. Quenching in 'Dragon Blood'
The secrets of Damascus steel were shared by armorers in many parts of the ancient world, notably in Persia, where some of the finest specimens were produced. It was in the quenching that many believed it acquired magical properties. According to Dr. Helmut Nickel, curator of the Arms and Armor Division of the Metropolitan Museum of Art in New York, legend had it that the best blades were quenched in ''dragon blood.''
In a recent letter to the museum a Pakistani told of a sword held in his family for many generations, quenched by its Afghan makers in donkey urine. Some medieval smiths recommended the urine of redheaded boys or that from a ''three-year-old goat fed only ferns for three days.''
For eight centuries the Arab sword makers succeeded in concealing their techniques from competitors -and from posterity. Those in Europe only revealed that they quenched in ''red medicine'' or ''green medicine.'' A less abrupt form of cooling, according to one account, was achieved when the blade, still red hot, was ''carried ina furious gal lop by a horseman on a fast horse.''
Writings found in Asia Minor said that to temper a Damascus sword the blade must be heated until it glows ''like the sun rising in the desert.'' It then should be cooled to the color of royal purple and plunged ''into the body of a muscular slave'' so that his strength would be transferred to the sword.
In the ancient accounts there is more than one reference to such homicidal quenching. In a recent interview, Dr. Nickel pointed out that while many of the quenching techniques were based on superstition, they may have contributed to the success of the process, as by adding nitrogen to the alloy.
Most, if not all, Damascus steel was derived from blocks of ''wootz,'' a form of steel produced in India. A mystery, to those seeking to recapture the technique, was the property of wootz that produced such blades - malleable when heated, yet extraordinarily tough when cooled. The Structure of Wootz
According to Dr. Wadsworth and Dr. Sherby, before doing his historic work on magnetism, Michael Faraday, himself the son of a blacksmith, sought with J. Stodart, a cutler, to determine the composition of wootz. They incorrectly concluded that the key factor was its silica and aluminum content.
Reports of their findings, published in 1820 and 1822, led Jean Robert Breant, Inspector of Assays at the Paris Mint, to conduct in a six-week period over 300 experiments seeking to reproduce the properties of wootz.
He tried adding to ordinary steel such elements as platinum, gold, silver, copper, tin, zinc, lead, bismuth, manganese, uranium, arsenic and boron. Anossoff even tried diamond. None of the efforts succeeded.
Wootz, it now appears, was apparently prepared in crucibles containing cakes of porous iron plus wood or charcoal to enrich it in carbon. A critical factor, Dr. Wadsworth said, appears to have been that the wootz was processed at temperatures as high as 2,300 degrees. After being held there for days, it was cooled to room temperature over a day or so. It was then shipped to the Middle East for relatively low-temperature fabrication.
This moderate heat preserved enough carbide (in which three atoms of iron are mated to one of carbon) to give the blades great strength, yet not enough to make them brittle. The large carbide grains gave the blades their typical watery pattern.
The superplastic steel developed at Stanford is kept at high temperature for only a few hours. It is shaped during cooling, reheated to moderate temperature for further working and may then be quenched to achieve extreme hardness. This process, Dr. Wadsworth said, produces very small carbide grains and hence even greater hardness and ductility than in Damascus steel.
According to Dr. Nickel, once blades of Damascus steel had been rough-shaped by hammering, they were ground to a fine edge. When they were hammered chiefly on one side, a curved shape resulted - the origin of the sabre, he said.
The finest blades ever made, he added, were the Samurai swords of Japan, whose blades may contain a million layers of steel. The layers resulted from hammering out a bar to double its original length, then folding it over as many as 32 times.
The multiple layers used by the Japanese and by makers of the Malay dagger or kris are sometimes referr ed to as ' 'welded Damascus steel.'' Although the production method diffe rs from that of true Damascus steel, the blades may show a very si milar pattern.
Dr. Wadsworth said a number of knife-making societies, such as The Anvil's Ring, which has 1,500 members, have sought to learn details of the Stanford findings. The research is described in Volume 25 of Progress in Materials Science, a British publication.
http://www.nytimes.com/1981/09/29/science/the-mystery-of-damascus-steel-appears-solved.html