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What mechanism primarily facilitates plastic deformation during cold working?
What mechanism primarily facilitates plastic deformation during cold working?
What is one of the main purposes of sintering in powder metallurgy?
What is one of the main purposes of sintering in powder metallurgy?
What characterizes the temperature-time curve during the solidification of metals?
What characterizes the temperature-time curve during the solidification of metals?
What happens to the temperature of a molten metal as it approaches its freezing temperature?
What happens to the temperature of a molten metal as it approaches its freezing temperature?
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What is the role of pressure during sintering?
What is the role of pressure during sintering?
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What is latent heat of fusion in the context of solidification?
What is latent heat of fusion in the context of solidification?
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What initiates the formation of crystalline nuclei during solidification?
What initiates the formation of crystalline nuclei during solidification?
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In the context of electroforming, what is the process primarily used for?
In the context of electroforming, what is the process primarily used for?
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What is a key characteristic of metals in solution?
What is a key characteristic of metals in solution?
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Which of the following is NOT a property of metals?
Which of the following is NOT a property of metals?
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What distinguishes metalloids from metals?
What distinguishes metalloids from metals?
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What is a method used for shaping metals?
What is a method used for shaping metals?
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Which of the following metals is liquid at room temperature?
Which of the following metals is liquid at room temperature?
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What property of metals contributes to their ability to conduct electricity?
What property of metals contributes to their ability to conduct electricity?
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Which two metals are notable for not being white?
Which two metals are notable for not being white?
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What cause allows metals to undergo plastic deformation?
What cause allows metals to undergo plastic deformation?
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What primarily causes elastic deformation in metals?
What primarily causes elastic deformation in metals?
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What is the localized shear region in a metal crystal called?
What is the localized shear region in a metal crystal called?
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What happens to the ductility of a metal when it undergoes cold working?
What happens to the ductility of a metal when it undergoes cold working?
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Which of the following best describes the process of recrystallization?
Which of the following best describes the process of recrystallization?
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What effect does cold working have on the strength of metals?
What effect does cold working have on the strength of metals?
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What is the term for the process of heating a cold worked metal to restore its properties?
What is the term for the process of heating a cold worked metal to restore its properties?
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What distinguishes wrought metals from other types of metals?
What distinguishes wrought metals from other types of metals?
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What occurs during the stress-relief anneal or recovery stage?
What occurs during the stress-relief anneal or recovery stage?
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What is the primary objective of homogenization in alloy processing?
What is the primary objective of homogenization in alloy processing?
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Eutectic alloys are characterized by which of the following properties?
Eutectic alloys are characterized by which of the following properties?
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Which statement correctly defines a cored structure within an alloy?
Which statement correctly defines a cored structure within an alloy?
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What describes the primary feature of intermetallic compounds formed upon solidification?
What describes the primary feature of intermetallic compounds formed upon solidification?
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Which one of the following statements about solid solution alloys is true?
Which one of the following statements about solid solution alloys is true?
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Why are eutectic alloys considered brittle?
Why are eutectic alloys considered brittle?
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What is a characteristic of the phase diagram for a binary system with complete insolubility?
What is a characteristic of the phase diagram for a binary system with complete insolubility?
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What effect does the cored structure have on the corrosion resistance of an alloy?
What effect does the cored structure have on the corrosion resistance of an alloy?
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What type of alloy is entirely soluble in both the liquid and solid states?
What type of alloy is entirely soluble in both the liquid and solid states?
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Which of the following is a condition for the formation of substitutional solid solutions between two metals?
Which of the following is a condition for the formation of substitutional solid solutions between two metals?
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What does the line ABC represent in a phase diagram?
What does the line ABC represent in a phase diagram?
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What occurs when there is a high chemical affinity between two metals?
What occurs when there is a high chemical affinity between two metals?
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In substitutional solid solutions, what characterizes the arrangement of atoms?
In substitutional solid solutions, what characterizes the arrangement of atoms?
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Which phase of an alloy is characterized by being partly liquid and partly solid?
Which phase of an alloy is characterized by being partly liquid and partly solid?
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What is the primary feature of coring in alloys?
What is the primary feature of coring in alloys?
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What is an example of an interstitial solid solution?
What is an example of an interstitial solid solution?
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What occurs during the stress-relief recovery process in metals?
What occurs during the stress-relief recovery process in metals?
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What is the primary reason for annealing cold worked structures before dental applications?
What is the primary reason for annealing cold worked structures before dental applications?
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What happens to the metal when it undergoes recrystallization at higher temperatures for extended periods?
What happens to the metal when it undergoes recrystallization at higher temperatures for extended periods?
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What is an effect of prolonged exposure to high temperatures during grain growth?
What is an effect of prolonged exposure to high temperatures during grain growth?
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What characterizes pure metals in terms of their suitability for dental applications?
What characterizes pure metals in terms of their suitability for dental applications?
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What is a binary alloy?
What is a binary alloy?
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When two molten metals are combined and cool, what could potentially happen?
When two molten metals are combined and cool, what could potentially happen?
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What characterizes the microstructure of solid solution alloys?
What characterizes the microstructure of solid solution alloys?
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Study Notes
Chapter 6: Metallurgy
- Metallurgy is the study of metals and alloys.
- A metal is an element that ionizes positively in solution.
- About 80 of the 103 listed elements in the periodic table are classified as metals.
- Valence electrons in metals are delocalized, unbound, and move throughout the metal rather than being bound to individual atoms.
- Nonmetals are on the right side of the periodic table. Metalloids/semiconductors are on the border between metals and nonmetals. They have characteristics of both. Examples include Carbon, Silicon, and Boron.
Properties of Metals
- Metals ionize positively in solution.
- Typically crystalline solids at normal temperature, with exceptions like mercury and gallium, which are liquid.
- Metals exhibit a distinctive luster, difficult to replicate in other solids. The luster arises from the response of unbound electrons to light frequencies, which reflects light.
Shaping of Metals
- Casting: Melting metal/alloy and shaping it in a mold to the desired shape.
- Cold Working: Mechanical working a solid metal block into rods, wires, tubes, or other shapes. The stresses applied are above the metal's yield strength, causing plastic deformation (slip along crystal planes involving dislocation movements).
- Powder Metallurgy (Sintering): Bonding solid particles by heat without a liquid. A process that eliminates initial porosity in a powder to create a denser product.
Solidification of Metals
- Cooling a melted metal produces a temperature-time curve.
- Temperature decreases from A to B, is constant until C, then decreases to room temperature.
- The freezing point (or fusion temperature) is indicated by a straight/flat portion (plateau BC) on the curve.
- During freezing, heat is released as the metal changes from liquid to solid; this is the latent heat of fusion.
Structure During Solidification
- Nuclei formation: atoms aggregate to form initial crystallization points (nuclei) at the supercooling point (homogeneous nucleation) or from existing solid particles (heterogeneous nucleation).
- Crystallization: Nuclei grow in three dimensions, forming crystals (grains). Growth stops when grains touch.
- Grain boundaries: Regions between crystals with different orientation where atoms are in distorted positions. Boundaries have higher energy.
- Grain boundaries impact mechanical properties (e.g., impact crystallization and diffusion).
Control of Grain Size
- Smaller grain sizes generally lead to better mechanical properties.
- Rate of cooling from the liquid state affects the number of nuclei that form during solidification, which in turn impacts grain size. Faster cooling results in smaller grains.
- Nucleating agents (grain refiners) can be added to increase the number of nuclei for smaller grain sizes.
Effect of Stress on Microstructure of Metals
- Elastic Deformation: Temporary deformation from stress below the elastic limit, directly related to the bonds of the metal.
- Plastic Deformation: Slip of atom layers over each other in certain planes. This process is characterized by dislocation movement within a localized zone (dislocation).
Wrought Metals
- Metals that were cold worked to form a fibrous structure from their cast or grain structures. This method includes techniques such as hammering, rolling, or drawing metals into wire.
Cold Working and Strain Hardening
- A plastically formed structure that's experienced above the yield point and ambient temperature.
- Cold working produces an increase in hardness, strength, and yield strength, but a reduction in ductility.
- Recovery, recrystallization, and grain growth are heat treatment processes that can reverse the effects of cold working.
Classification of Alloys
- Alloys are combinations of two or more metals.
- Classified according to the number of alloying elements (binary, ternary, etc.).
- Classified according to miscibility of constituent atoms (solid solution alloys, eutectic alloys, intermetallic compounds).
(1) Solid Solution Alloys
- Metals that are completely soluble in each other in both liquid and solid states.
- Substitutional: different atoms fill different positions in the same crystal lattice.
- Interstitial: smaller atoms fit into spaces between larger atoms in the lattice.
(2) Eutectic Alloys
- Lowest melting alloy in a given system.
- Cooling curve has a horizontal plateau at the eutectic temperature.
- Often brittle due to heterogeneous phase structure.
- Used for soldering due to low melting temperature.
(3) Intermetallic Compounds
- Formed due to chemical affinity between constituent metals.
- Intermetallic compounds typically have unique properties (e.g., hardness, brittleness) compared to their constituent metals.
- Solid-state reactions are temperature assisted diffusion in metals where it is useful for homogenization in alloys.
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Description
Explore Chapter 6 on Metallurgy, where we dive into the study of metals and alloys. Learn about the properties of metals, including their behavior in solutions and their crystalline structures. Understand the shaping processes of metals and their unique characteristics.
