Application And Processing Of Metal Alloys Flashcards
2 groups of metal alloys
Ferrous and nonferrous
Principal constituents of ferrous alloy
Iron
produced in larger quantities than any other metal type
Ferrous alloys
Factors for the use of ferrous alloys
Abundant quantities
Economical extraction
Extremely versatile
principal disadvantage of many ferrous alloys
susceptibility to corrosion
iron–carbon alloys that may contain appreciable concentrations of other alloying elements
Steel
contain only residual concentrations of impurities other than carbon and a little manganese
Plain carbon steels
Of all the different steels, those produced in the greatest quantities
Low-carbon steel
Microstructures consist of ferrite constituents
Low-Carbon Steel
relatively soft and weak but have out standing ductility and toughness
Low-Carbon Steel
contain other alloying elements such as copper, vanadium, nickel
High-strength, low-alloy Steel
may be strengthened by heat treatment, they are ductile, formable, and machinable
High-strength low-alloy steel
more resistant to corrosion than the plain carbon steels
High-strength, low-alloy steel
contain less than about 0.25 wt% C and are unresponsive to heat treatments intended to form marten site
Low-Carbon steel
have carbon concentrations between about 0.25 and 0.60 wt%
Medium-Carbon steel
These alloys may be heat-treated by austenitizing, quenching, and then tempering to improve their mechanical properties.
Medium-Carbon steels
often utilized in the tempered condition, having microstructures of tempered marten site
Medium-Carbon Steels
have low harden abilities and can be successfully heat-treated only in very thin sections and with very rapid quenching rates
Medium-Carbon Steels
responsible for the classification and specification of steels as well as other alloys
SAE, AISI, ASTM
having carbon contents between 0.60 and 1.4 wt%
High-carbon steel
hardest, strongest, and yet least ductile of the carbon steels
High-carbon steel
almost always used in a hardened and tempered condition and, as such, are especially wear resistant and capable of holding a sharp cutting edge
High-carbon steel
usually containing chromium, vanadium, tungsten, and molybdenum
High-carbon steel
highly resistant to corrosion (rusting) in a variety of environments, especially the ambient atmosphere
Stainless steel
predominant alloying element is chromium (11%wt)
Stainless steel
Classes of stainless steel
Martensitic, ferritic, or austenitic
capable of being heat-treated in such a way that martensite is the prime microconstituent.
Martensitic stainless steel
composed of the a-ferrite (BCC) phase
Ferritic stainless steel
Austenitic and ferritic stainless steels are hardened and strengthened by_________
Cold work
most corrosion resistant because of the high chromium contents and also the nickel additions
Autenitic stainless steel
martensitic and ferritic stainless steels are
Magnetic
class of ferrous alloys with carbon contents above 2.14 wt%
Cast iron
is a meta stable compound, and under some circumstances it can be made to dissociate or decompose to form α-ferrite and graphite
Cementite
carbon exists as graphite, and both microstructure and mechanical behavior depend on composition and heat treatment
Cast iron
carbon and silicon contents of gray cast irons vary between 2.5 and 4.0 wt% and 1.0 and 3.0 wt%, respectively
Gray iron
graphite exists in the form of flakes
Gray iron
weak and brittle in tension but strength and ductility are much higher under compressive loads
Gray iron
Adding a small amount of magnesium and/or cerium to the gray iron before casting, Graphite forms as nodules or sphere
Nodule iron
most of the carbon exists as cementite
White iron
extremely hard but also very brittle
White iron
has a wormlike (or vermicular) shape
Compacted graphite iron
Alloys thatare so brittle that forming or shaping by appreciable deformation is not possible typically are cast
Cast alloys
amenable tomechanical deformation
Wrought alloy
have been utilized in quite a variety of applications since antiquity
Copper and copper based alloy
soft and ductile that it is difficult to machine
Unalloy copper
highly resistant to corrosion in diverse environments including the ambient atmosphere, seawater, and some industrial chemicals
Copper
most common heat-treatable copper alloys
Beryllium copper
characterized by a relatively low density (2.7 g/cm3 as compared to 7.9 g/cm3 for steel), high electrical and thermal conductivities, and a resistance to corrosion in some common environments, including the ambient atmosphere
Aluminum
Its chief limitation is low melting temperature
Aluminum
its alloys are used where light weight
Magnesium
has an HCP crystal structure, is relatively soft, and has a low elastic modulus: 45 GPa (6.5X106 psi) and at room temperature it is difficult to deform
Magnesium
possess an extraordinary combination of properties and its alloys are highly ductile and easily forged and machined.
Titanium
Metals that have extremely high melting temperatures
Refractory metal
Interatomic bonding in these metals is extremely strong, which accounts for the melting temperatures, large elastic modulus and high strengths and hardnesses at ambient as well as elevated temperatures
Refactory metal
withstand exposure to severely oxidizing environments and high temperatures for reasonable time periods
Super alloy
Soft , Ductile , Oxidation Resistant
Noble metal
highly resistant to corrosion in many environments, especially those that are basic (alkaline)
Nickel
mechanically soft and weak, have low melting temperatures, are quite resistant to many corrosion environments, and have recrystallization temperatures below room temperature.
Lead and tin
Fabrication Techniques
Casting, powder metallurgy, welding and machining
Plastic deformation
Forging, rolling, extrusion and drawing
When deformation is achieved at a temperature above that at which recrystallization occurs
Hot working
mechanically working or deforming a single piece of a normally hot metal
Forging
accomplished by the application of successive blows or by continuous squeezing
Forging
classified as either closed or open die
Forging
force is brought to bear on two or more die halves having the finished shape
Close die
used in the production of sheet, strip, and foil with a high quality surface finish
Cold rolling
fabricated using grooved rolls that have rather complicated cross-sectional geometries
Rails
bar of metal is forced through a die orifice by a compressive force thatis applied to a ram
Extrusion
pulling of a metal piece through a die having a tapered bore by means of a tensile force that is applied on the exit side
Drawing
fabrication process whereby a totally molten metal is poured into a mold cavity having the desired shape
Casting
two-piece mold is formed by packing sand around a pattern that has the shape of the intended casting
Sand Casting
usually incorporated into the mold to expedite the flow of molten metal into the cavity and to minimize internal casting defects
Gating system
liquid metal is forced into a mold under pressure and at a relatively high velocity and allowed to solidify with the pressure maintained
Die Casting
two piece permanent steel mold or die is employed
Die casting
pattern is made from a waxor plastic that has a low melting temperature.
Investment casting
What is usually used in investment casting
Plaster in paris
Variation of investment casting
Lost foam
the expendable pattern is a foam that can be formed by compressing polystyrene beads into the desired shape and then bonding them together by heating
Lost-foam casting
simpler, quicker, and less expensive process and there are fewer environmental wastes
Lost foam casting
What are the metal alloys that most commonly use in loastgfoam casting technique
cast irons and aluminum alloys
refined and molten metal is cast directly into a continuous strand that may have either a rectangular or circular cross section
Continous casting
involves the compaction of powdered metal followed by a heat treatment to produce a denser piece
Powder metallurgy
This method is especially suitable for metals having low ductilities
Powder metallurgy
two or more metal parts are joined to form a single piece when one-part fabrication is expensive or inconvenient
Welding
refers to a heat treatment in which a material is exposed to an elevated temperature for an extended time period and then slowly cooled
Annealing
heat treatment that is used to negate the effects of cold work
Process annealing
commonly used during fabrication procedures that require extensive plastic deformation, to allow a continuation of deformation without fracture or excessive energy consumption
Process annealing
Remove the residual stresses produced by distortion and warpage
Stress relieve
heat treatment in which the piece is heated to the recommended temperature, held there long enough to attain a uniform temperature, and finally cooled to room temperature in air
Stress relief annealing
horizontal line at the eutectoid temperature
Lower critical temperature
annealing heat treatment used to refine the grains
normalizing
alloy have completely transform to austenite
Austenitizing
heat treatment often used in low- and medium-carbon steels that will be machined or will experience extensive plastic deformation during a forming operation
full annealing
heat treatment normally carried out at a temperature just below the eutectoid
Spheroiding
describe the ability of an alloy to be hardened by the formation of martensite as a result of a given heat treatment
Hardenability
qualitative measure of the rate at which hardness drops off with distance into the interior of a specimen as a result of diminished martensite content
Hardenability
standard procedure widely used to determine hardenability
Jominyend-quench test
induced by appropriate heat treatments
Precipitate hardness
Heat treatment used in precipitate hardening
Solution heat treatment
Precipitate heat treatment
solute atoms are dissolved to form a single phase solid solution
Solution heat treatment
heat treatment used to precipitate a new phase from a supersaturated solid solution
Precipitation heat hardening
commonly employed with high-strength aluminum alloys
Precipitation hardening
