When the concentration of solute in a solid solution exceeds the solubility limit, which of the following situations results?
A. The formation of a new solid solution or phase that has a composition similar to that of the original solid solution.
B. The formation of a new solid solution or phase that has a distinctly different composition than the original solid solution.
-B. The formation of a new solid solution or phase that has a distinctly different composition than the original solid solution.
Once a system is at a state of equilibrium, a shift from equilibrium may result by alteration of which of the following? A. Pressure B. Composition C. Temperature D. All of the above
-D. All of the above
Define triple point as it related to a single component phase diagram.
-The only point in the phase diagram where all three states are in equilibrium
A solidus line separates which of the following phase fields? A. Liquid and liquid+alpha B. Alpha and liquid+alpha C. Alpha and alpha+beta D. Liquid+alpha ans alpha+beta
-B. Alpha and liquid+alpha
Define critical point as it relates to a single component phase diagram.
- The highest temperature and pressure at which a liquid and a gas can co-exist at equilibrium.
- Beyond that the liquid and gas phase are indistinguishable.
State three variables that determine the microstructure of an alloy.
- The alloying elements present
- The concentrations of the alloying elements present
- The heat treatment of the alloy
Define eutectic temperature as it relates to binary eutectic systems phase diagram.
- Along with the eutectic composition (CE) it is the eutectic or invariant point
- Where the liquid and two solid phases coexists in equilibrium
- It is the lowest possible melting temperature for all of the mixing ratios of the components
What do you understand by lamellar eutectic structure? When are they formed?
- Co = CE
- Lamellar structure = eutectic microstructure
- alternating layers (lamellae) of alpha and beta crystals
What is the primary difference in ferrous steels and cast irons
-Alloy metals that contain iron (primary base metal is iron)
State two limitations in properties for the application of ferrous alloys
- Relatively high density
- Relatively low conductivity
- Poor corrosion resistance
State and briefly describe three types of stainless steel
- Ferritic: Iron-chromium alloys
- BCC crystal structure, Cr (11-30%), C (up to 0.2%)
- Good ductility
- Relatively weak
- Used in architectural trim, kitchen range hoods, jewelry, decorations, utensils
- Austentitic: Iron-nickel-chromium alloys
- Cr (16-26%), C (up to 0.2%), Ni, Mn, Mo non-magnetic
- Marchinable
- Weldable
- Relatively weak
- Used in architectural products, storefronts, doors and windows, railings; chemical processing, food utensils, kitchen applications - Martensitic: Iron-chromium-carbon alloys
- Cr (10-12%), C (less than 1.2%)
- High strength
- Hardness
- Resistance to abrasion
- Used in turbine parts, bearings, knives, cutlery and generally magnetic
Differentiate between hot and cold working of metals
- Hot working
- Temperature high enough for re-crystallization
- Larger deformations
- Cold working
- Well below Tm
- Work hardening
- Smaller deformations
Name and describe two metal forming methods.
- Casting
- Powder Metallurgy
Describe the process of metal casting to form final metallic products
- Mold is filled with metal
- Metal melted in furnace, perhaps alloying elements added. Then cast in a mold
- Most common, cheapest method
- Gives good production of shapes
- Weaker products, internal defects
- Good option for brittle materials
Describe briefly the powder metallurgy fabrication method
- Materials with low ductility
- ~the production and working of metals as fine powders that can be pressed and sintered to form objects
What is annealing?
- The process whereby heat is introduces to mobilize the atoms and relieve internal stress
- After annealing, it allows the metal to be further shaped
- It involves the re-crystallization of the distorted structure
Differentiate between annealing and quenching
- Annealing
- The process whereby heat is introduces to mobilize the atoms and relieve internal stress
- After annealing, it allows the metal to be further shaped
- It involves the re-crystallization of the distorted structure
- Quenching
- Rapid cooling in quenching medium such as water or oil
- Depends on
- Composition of alloy
- Type of quenching medium
- Size and shape of specimen
