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A D V A N C E D
M A T E R I A L S
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P R O C E S S E S |
M A R C H
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tests and examined the results using ad-
vanced TEM techniques and quantum
mechanical predictions of defect struc-
tures. They found that the interactions
between oxygen and the crystalline
defects, known as dislocations, that are
characteristic of titanium were key to
how the material hardened.
Oxygenatoms act likebumps in the
road for the corkscrew-shaped disloca-
tions found in titanium. “The mechani-
cal shuffling that occurs as dislocations
pop up and over those atomic bumps
creates a domino effect of more dislo-
cations,” says Minor. With increased ox-
ygen, titanium becomes more difficult
to bend and therefore more suscepti-
ble to cracking. For more information:
Andrew Minor, 510.495.2749,
, .
RECIPE FOR LIGHTER,
STRONGER STEEL
Scientists at Pohang University of
Science and Technology, South Korea,
are improving lightweight steel by alter-
ing how metal compounds are arrayed
in an alloy. The microstructure of their
material is even stronger and more pli-
able than titanium alloys.
One possible structure in steel is
B2—a hard, brittle cube formation. Iron
and aluminum tend to form B2 struc-
tures in steel alloys, but scientists usu-
ally try to prevent this by adjusting the
temperature or adding other elements.
Researchers made a steel that takes
advantage of both B2’s hardness and
austenite’s ductility. By adding nickel
and temperature-treating an alloy of
iron, aluminum, manganese, and car-
bon, they induced smatterings of B2 to
form evenly throughout the steel. The
resulting material, in which the hard B2
lattices reinforce the supple austenite
matrix, has impressive tensile strength.
A recipe for lighter, stronger steel adds nickel to an alloy of iron, carbon, aluminum, and
manganese. Courtesy of Imaginechina/Corbis.