Week 1b written
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Arizona State University *
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107
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Material Science
Date
Dec 6, 2023
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Uploaded by CaptainHeat457
2. Chapter 1
1.
Why does a razor blade get dull (blunt)? Explain.
Each of the crystals that make up a razor blade includes billions of atoms that are arranged in a
precise, three-dimensional pattern. The crystal's strength comes from the bonds that hold the
atoms together and keep them from moving. When a razor blade cuts through hair, it collides
with it and causes the crystals to reorganize into a different shape, which causes the blade to
become dull. This causes the bond to break down, which ultimately causes the razor edge to
develop small dents.
2.
Why is re-sharpening a razor blade a challenge?
Re-sharpening a razor blade is a challenge because heat softens metal crystals. Heat can affect
the hardness and temper of the blade material. When re-sharpening a razor blade, high heat may
affect the blade's structure and result in unwanted modifications to its qualities. Heat may be
produced during re-sharpening a blade because of friction between the blade and the sharpening
instrument. The blade's hardness and temper may be impacted by localized temperature rises
brought on by this heat. Too much heat might cause the blade to soften, lose its hardness, or even
undergo unfavorable changes in its microstructure.
3.
Explain the significance of dislocations. Include connections to malleability and
melting points.
Dislocations are atomic disruptions that shouldn't be there and are considered flaws in the metal
crystals since they deviate from the normally ideal crystalline arrangement of the atoms.
However, they are crucial because metals can alter shape thanks to dislocations. The ease with
which the dislocations move is also influenced by a metal's melting point, which measures how
firmly the metal atoms are held together. As a result, a metal with a low melting point is brittle,
whereas one with a high melting point is stronger. Metals become softer as a result of heating
because it allows dislocations to move about and reorganize themselves.
4.
How was copper discovered? How was it originally made?
Copper was first discovered by early humans who were experimenting with various rocks and
minerals in prehistoric times. Malachite was placed into a hot fire surrounded by red-hot embers
in order to detect copper. The somewhat greenish rock changed into a bright metal object. Other
rocks were attempted, but not all of them were successful. Early metalsmiths refined the method
of producing copper through trial and error.
5.
What is an alloy? Compare properties of alloys with pure metals. Explain the
differences.
Alloy is the process of combining different metals to produce a new element with enhanced
qualities compared to pure metals. Because the alloy atoms differ in size and chemistry from the
host metal's atoms, they cause a variety of mechanical and electrical disturbances inside the host
crystal that all add up to one very important thing: they make it harder for dislocations to move.
This is why alloys tend to be stronger than pure metals. Additionally, if dislocations find it
difficult to shift, the metal is stronger since the metal crystals have a tougher time changing
shape. Thus, the magic of alloy design is to stop dislocations from moving.
6.
What is steel?
Steel is an alloy of iron, carbon, and other elements. Our ancestors were unaware that steel was
an alloy and that carbon, in the form of charcoal, could penetrate the iron crystals as well as be
used to heat and reshape iron.
Steel's carbon content can be regulated during the manufacturing
process, giving rise to several types and grades of steel with unique properties. It is an
extensively used material in many different sectors and applications because of its excellent
strength, toughness, and adaptability.
7.
What is the source of carbon in steel?
Charcoal is the source of the carbon in steel. Since it was a popular fuel source and produced a
lot of heat, charcoal was employed in the furnaces because of its high carbon content. However,
there was little control over how much charcoal was used and how it interacted with the iron or
steel that was being produced. The carbon content of charcoal produced from various kinds of
wood or under various circumstances may vary. This could lead to variable carbon levels in the
steel produced, together with the lack of exact control over the input of charcoal.
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8.
Why doesn’t carbon create an alloy with copper, tin or bronze during smelting?
What is unique about iron?
During the smelting process, carbon does not combine with copper, tin, or bronze because it
behaves differently in those metals than it does in iron. The carbon atoms in metals like copper,
tin, and bronze don't get along well with the other metal atoms. Instead of integrating into the
metal structure, it would want to remain separate. It creates different stages or compounds all on
its own. Contrarily, when carbon and iron meet, a special reaction takes place. Iron can
accommodate carbon, which integrates into the iron's structure. Carbon differs from other metals
in that it may dissolve into the iron lattice. According to the amount of carbon present, it
continuously mixes with iron to produce various types of steel.
9.
Explain how ancient samurai swords were made.
These samurai swords were handmade from a unique sort of steel called tamahagane and were
created from the Pacific's volcanic black sand, which is primarily made of magnetite, the iron ore
that served as the compasses' initial needle. The enormous clay tatara is used to create this steel.
By starting a fire inside the vessel, the molded clay is fired to solidify it into ceramic. After being
fired, it is painstakingly layered with black charcoal and sand, which are burned in the ceramic
furnace. A group of four or five people must be on hand at all times during the process, which
lasts about a week. They must ensure that the fire's temperature is kept high enough by manually
forcing air into the Tatara using bellows. At the conclusion, the Tatara is split apart, and the steel
from the tamahagane is excavated from the ash and remaining sand and charcoal. These lumps of
discolored steel differ in carbon content from extremely low to very high, making them very
variable in appearance. They could ensure that the low-carbon steel was used to create the
sword's center by segregating the various types of steel.
10. What is the Bessemer process?
The Bessemer process was the first low-cost industrial method for producing large amounts of
steel. In order for the oxygen in the air to interact with the carbon in the iron and extract it as
carbon dioxide gas, it required blowing air through the molten iron. It required chemistry
knowledge, which gave steelmaking a scientific foundation. Furthermore, a great deal of heat
was produced by the exceedingly violent reaction between the oxygen and the carbon. The steel's
temperature was boosted by this heat, keeping it hot and liquid.
11. How was stainless steel discovered? How does it work?
Harry Brearley was given the responsibility of researching metal alloys in order to improve
cannon barrels. He performed experiments with the addition of various elements to steel, and
cast samples, and evaluated the hardness of those materials while working in a metallurgical lab
in Sheffield, England. Even though the composition of steel was known to be iron and carbon,
the impacts of other elements were not yet well understood.
Brearley performed experiments using trial and error by melting steel and adding various
substances to determine their effects. Brearley made little progress at first, discarding samples
that didn't fit his standards for hardness. After a month of work, he finally made a breakthrough
when he discovered a shining specimen amidst the collection of rusting samples. He didn't ignore
it; he understood its importance. It turned out to be the first stainless steel object ever made. By
accident, Brearley had balanced the alloy's carbon and chromium content to produce a distinctive
crystal structure. Chromium wasn't added to the steel to make it harder; instead, it had a more
intriguing impact.
Iron on steel's surface typically reacts with oxygen and water to produce iron(III) oxide, also
known as rust. Rusting issues are brought on when this rust peels off, exposing the underlying
steel to more corrosion. But when chromium was present, something unusual happened. Before
the iron atoms could react with oxygen, chromium did, forming chromium oxide, a clear and
resilient mineral. Contrary to rust, chromium oxide attaches effectively to steel, creating a
chemically protective layer that is completely undetectable. This layer also has a remarkable
capacity for self-healing. The stainless steel can rebuild itself, keeping its protective qualities
even if it is scraped and the barrier is broken.
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