19
Sometime around 3000 BC the probably accidental inclusion of a
tin-based mineral, cassiterite, in the copper ores provided the next
step in technology: the production of the alloy bronze, a mixture
of tin and copper. Tin gives bronze an additional hardness that pure
copper cannot match, allowing the production of superior tools
and weapons. This discovery of alloying and solid solution strengthening—the hardening of one metal by adding another—was of
such importance that it, too, became the name of a new era: the
Bronze Age.
“Old-fashioned” sounds like 20
th century vocabulary, but the phenomenon is as old as technology itself. The discovery, around 1450
BC, of ways to reduce ferrous oxides to make iron, a material with
greater stiffness, strength, and hardness than any other then available, rendered bronze old-fashioned. Iron was not entirely new;
tiny quantities existed as the cores of meteors that had impacted
the Earth. The oxides of iron, by contrast, are widely available,
particularly hematite, Fe 2 O 3 . Hematite is easily reduced by carbon,
although it takes high temperatures, close to 1100°C, to do it. This
temperature is insufficient to melt iron, so the material produced
was a spongy mass of solid iron intermixed with slag; this was
reheated and hammered to expel the slag and then forged into the
desired shape.
Iron revolutionized warfare and agriculture; indeed, it was so desirable that at one time it was worth more than gold. The casting of
iron, however, was a more difficult challenge, requiring temperatures around 1600°C. Two millennia passed before, in 1500 AD,
the blast furnace was developed, enabling the widespread use of
cast iron. Cast iron allowed structures of a new type; the great
bridges, railway terminals, and civic buildings of the early 19
th
century are testimony to it.
But it was steel, made possible in industrial quantities by the
Bessemer process of 1856, which gave iron its dominant role in
structural design that it still holds today. The demands of the
expanding aircraft industry in the 1950s, with the development of
the jet engine, shifted emphasis to light alloys (those of aluminum,
magnesium, and titanium) and to materials that could withstand
the extreme temperatures of the jet combustion chamber. The
development of superalloys—heavily alloyed iron- and nickelbased materials—became the focus of research, delivering an
extraordinary range of alloys able to carry loads at temperatures
above 1200°C. The range of their applications expanded into other
fields, particularly those of chemical and petroleum engineering.
A Brief History of Materials
Sometime around 3000 BC the probably accidental inclusion of a
tin-based mineral, cassiterite, in the copper ores provided the next
step in technology: the production of the alloy bronze, a mixture
of tin and copper. Tin gives bronze an additional hardness that pure
copper cannot match, allowing the production of superior tools
and weapons. This discovery of alloying and solid solution strengthening—the hardening of one metal by adding another—was of
such importance that it, too, became the name of a new era: the
Bronze Age.
“Old-fashioned” sounds like 20
th century vocabulary, but the phenomenon is as old as technology itself. The discovery, around 1450
BC, of ways to reduce ferrous oxides to make iron, a material with
greater stiffness, strength, and hardness than any other then available, rendered bronze old-fashioned. Iron was not entirely new;
tiny quantities existed as the cores of meteors that had impacted
the Earth. The oxides of iron, by contrast, are widely available,
particularly hematite, Fe 2 O 3 . Hematite is easily reduced by carbon,
although it takes high temperatures, close to 1100°C, to do it. This
temperature is insufficient to melt iron, so the material produced
was a spongy mass of solid iron intermixed with slag; this was
reheated and hammered to expel the slag and then forged into the
desired shape.
Iron revolutionized warfare and agriculture; indeed, it was so desirable that at one time it was worth more than gold. The casting of
iron, however, was a more difficult challenge, requiring temperatures around 1600°C. Two millennia passed before, in 1500 AD,
the blast furnace was developed, enabling the widespread use of
cast iron. Cast iron allowed structures of a new type; the great
bridges, railway terminals, and civic buildings of the early 19
th
century are testimony to it.
But it was steel, made possible in industrial quantities by the
Bessemer process of 1856, which gave iron its dominant role in
structural design that it still holds today. The demands of the
expanding aircraft industry in the 1950s, with the development of
the jet engine, shifted emphasis to light alloys (those of aluminum,
magnesium, and titanium) and to materials that could withstand
the extreme temperatures of the jet combustion chamber. The
development of superalloys—heavily alloyed iron- and nickelbased materials—became the focus of research, delivering an
extraordinary range of alloys able to carry loads at temperatures
above 1200°C. The range of their applications expanded into other
fields, particularly those of chemical and petroleum engineering.
A Brief History of Materials