Another technology for improved blades; developed in Toledo, Spain in the 11th century was peening.
http://www.badgermetal.com/pdf/dce-residual-stress-sep2007-Part1-jan2008-Part2.pdf
"During the 11th Century, a special brand of European
swords were produced that had improved performance
along with resistance to breakage. Most swords at the time
were thick and heavy to keep them from breaking. A broken
sword in battle meant permanent downtime and probable
doom to the user. These heavy swords, however, took
more physical energy and strength to swing, which slowed
down the user's reaction time…also not a good thing.
If you had the money or were a king, you could go to Toledo,
Spain, and buy the newest technology in swords. The cunning
Toledo blacksmiths had developed a thinner, lightweight,
well-balanced weapon that would hold a sharp edge and could
be bent almost double, over and over, without breaking. No
other sword makers could produce such an indestructible
battle weapon, which made the Toledo swords famous to this
day. Their art was never revealed, even after swords gave way
to firearms. Even metallurgists who examined the blade's steel
composition, heat treatment and finishing were unable to find
the secret to these break resistant weapons.
In the 1970s, science again delved into the mystery
of the Toledo blades. This time they re-examined them
using modern X-ray diffraction methods for measuring
compressive stress. To their surprise, they found that the
blades had been peened, not with shot as is done today,
but with ball peen hammers. Who would have figured that
in the 11th century these smart blacksmiths were using a
basic technology that today is used in many products and
industries but is not as well accredited, as it should be,
especially in die casting?"
