ME215 Exam 2 Study Guide
Addition
- A number of basic units (monomer) link together to form a large molecule (polymer) in which there is a repeated unit (mer)
Heat Treatment
- A process of controlled heating and cooling of materials for the purpose of altering their structures and properties, which changes in physical and mechanical properties can be introduced with no change in product shape
Advanced High-Strength Steels (AHSS)
- AHSS is primarily ferrite-phase, soft steels with varying amount of martensite, bainite or retained austenite - which offers high strength with enhanced ductility - Improved formability - Possibility of weight reduction
Superalloys and other metals designed for high-temperature service
- Alloys based on nickel, iron, cobalt - Refractory metal: niobium, molybdenum, tantalum, rhenium, and tungsten - Intermetallic compounds
Altered Surface Chemistry
- Carburizing - Nitriding - Ionitriding - Ion Carburing - Carbonitriding - Nitrocarburizing
Process Anneal
- Cooling in air
Normalizing
- Cooling in air - Cooling will be different in different locations - Properties will vary between the surface and interior
Annealing
- Cooling in furnace - Cost effective and time consuming - The furnace imposes cooling conditions at all locations - Result in identical structures and properties
Cold Treatment and Cryogenic Processing
- Cooling into sub-zero temperature with dry ice or liquid nitrogen - It can complete austenite to martensite transformation and increase strength and hardness - Improve wear resistant - Longer lifetime
Types of AHSS
- Dual Phase Steels - Transformation-Induced Plasticity Steels - Complex-Phase Steels -Martensitic Steels
Residue Stress
- Exist in a part independent of an applied stress - Undesirable residual stresses result in cracking, warping, dimensional changes
Selective heating of the surface
- Flame Hardening - Induction Hardening - Laser Beam Hardening - Electron Beam Hardening
Copper and Copper Alloys
- High electrical and thermal conductivity - Useful strength with high ductility - Corrosion Resistance
Ceramic
- High temperature usage - Hard and brittle - High melting point - Low thermal expansion - Good creep resistance - High compressive strength
Thermosets
- Highly cross-linked or three-dimensional framework structure - Produced by condensation polymerization - Irreversible Reaction at elevated temperature - material is unable to recycle
Deposition of an Additional Surface Layer
- Ion Plating - Ion Implantation
Plastic
- Large molecules that are built up by the joining of smaller molecules - Low density, low tooling costs, good corrosion resistance, low cost
Lead and Tin, and their alloys
- Lead and lead alloys - provide high density with strength and stiffness that are the lowest of engineering metals - Tin - use as a corrosion resistant coating on steel - Lead and tin are used together as bearing materials and solder
Magnesium and magnesium alloys
- Lightest of commercially important materials - Poor wear, creep and fatigue properties - Highest thermal expansion of all engineering metals - Modulus of elasticity is less than that of alminum - High energy absorption and good damping
Thermoplastics
- Linear Polymer - Heat-softening material - Reversible reaction at elevated temperature
Elastomer or Elastic Polymer
- Linear polymer with large amount of elastic deformation when a force is applied
Microalloyed Steels
- Low and medium carbon steels with small amounts of alloying elements - Offer maximum strength with minimum carbon - Preserves weldability, machinability, and formability
Bake-Hardenable Steel
- Low carbon steel that is resistant to aging during normal storage, but begins to age during sheet metal forming - A significant role in automotive applications
Ways to prevent quench cracking and residual stresses
- More uniform cross-sectional area - Generous fillets at interior area - Radiused exterior corners - Smooth transitions - Adding additional holes
Precipitation Hardening
- Most effective mechanism to strengthen nonferrous metals - Non-equilibrium heat treatment procedure
Nickel-Based Alloy
- Outstanding strength and corrosion resistance at high temperatures - Good formability, creep resistance, strength and ductility at low temperatures - Wrought alloys are known as Monel, Hastelloy, Inconnel, Incoloy, and others
HSLA
- Provide increased strength to weight ratio - Modest increase in cost - High yield strength, good weldability, and good corrosion resistance
Recrystallization Anneal
- Recrystallization is induced after a material has been cold worked to reduce strain hardening effects - Induces a change in size, shape and distribution
Stress-Relief Anneal
- Reduces residual stresses - Materials are heated and then slow cooled - Microstructures and mechanical properties remain unchanged
Spheroidizing Anneal
- Slow cooling - For high carbon materials
Titanium and Titanium Alloys
- Strong lightweight, corrosion resistant metal - Less dense than steel, high strength-to-weight ratio - Can be used in high temperature applications - High cost, fabrication difficulties, high energy costs for fabrications
Pre-coated Steel Sheet
- The coating is applied when steel is still in the form of a long, continuous strip - To reduce the cost and time consuming in finishing process
Causes of dimensional changes during heat treatment
- Thermal expansion during heating and thermal contraction during cooling - Volume expansion and contraction
Fiber-reinforced Composites
- They are composite that continuous or discontinuous thin fibers of one material are embedded in a matrix - Common objective is high strength and lightweight
Quenchant Consideration
- Water is an effective quenching medium because of its high heat of vaporization and relatively high boiling point - Brine is similar to water as a quenchant medium - Oil is utilized if slower quenching rates are desired - Water based polymer quenchants have properties between oil and water and brine - Other slow cooling quenchants: Molten salt baths, cooling in air, bury the hot material in sand, etc.
Types of tool steels
- Water-hardening tool steels - Cold-work steels - Shock resisting tool steels - High speed tool steels - Hot-work steels - Plastic mold steels - Special purpose tool steels
Aluminum and Aluminum Alloys
- Workability - Light weight - Corrosion Resistance - Thermal and electrical conductivity - Optical reflectivity - Easily finished
Processing heat treatments are used to...
- increase strength - prepare the material for fabrication - improve machining characteristics - reduce forming forces - restore ductility for further processing
General Sequence of Product Design
1. Design 2. Material Selection 3. Process Selection 4. Production 5. Evaluation 6. Redesign / Modification
Vacuum Degassing
A stream of molten metal passes through a vacuum chamber into a mold
Martensitic Steels
Almost entirely martensite
Steels for Electrical and Magnetic Applications
Amorphous Metals - No crystal structure , grains, or grain boundaries - Magnetic domains can move freely - Properties are the same in all directions - Corrosion resistance is improved
Austempering
Austenite -> Bainite, rapidly quench into liquid medium 15 degrees celcius above Martensite start temperature and held for sufficient time
Martempering
Austenite -> Martensite, rapidly quench into liquid medium 15 degrees celcius above Martensite start temperature and slow cool in air through martensite transformation
Degree of Polymerization
Average number of mers in polymer
Medium-Carbon Steel
Balanced properties
Terpolymer
Combining three different monomers
Compacted graphite cast iron
Compacted graphite is intermediate to flake graphite of gray cast iron and nodular graphite of ductile iron
Steel Processing
Continuous casting produces feedstock material (slab, bloom, billet, strand) that is used in forging or rolling, steel have large amount of oxygen dissolved in molten metal
Oxidation Process
Decreases the amount of carbon, silicon, manganese, phosphorous, and sulfur in pig iron or steel scrap
Dispersion Hardening
Dispersing second-phase particles through a base material
Aging Step
Divide precipitation-hardening materials into two types: natural aging materials (ages at room temperature) and artificial aging material (requires elevated temperature to produce aging)
Austempered ductile iron
Ductile cast iron which go to austempering heat treatment - provide double strength with same ductility compared to ductile cast iron, excellent strength-to-weight ratio
High-alloy cast iron
Enhance corrosion resistance and/or good elevated temperature service
Low-Carbon Steel
Excellent ductility and fracture resistance but lower strength
White Cast Iron
Excess carbon in form of iron-carbide - hard and brittle
Casting Processes
Exploit the properties of a liquid as its flow into and flows into and assumes the shape of a prepared container, and the solidifies upon cooling
High-Strength Low-Alloy Structural Steels (HSLA)
Focus on product (size and shape) and desired properties
Stages of Quenching
Formation of the vapor jacket -> Nucleate boiling phase -> Conduction and convection
AISI SAE Classification System
Four-digit number - First number indicates the major alloying elements - Second number designates a sub-grouping within the major alloy system Last two digits indicate the carbon Percentage expressed as "points"
Graphite
Good thermal and electrical conductivity, can withstand high temperatures and lubricity
Grey Cast Iron
Graphite flakes
Phase transformations
Heated to form a single phase at an elevated temperature and subsequently transform to one or more low temperature phases upon cooling (austenite -> martensite)
Tool Steels
High carbon, high strength, ferrous alloys that have a balance of strength, toughness, and wear resistance
High-Carbon Steel
High strength and hardness but at the the expense of ductility and fracture resistance
Strain Hardening
Increases strength by plastic deformation
Malleable Cast Iron
Irregularly shaped cluster of graphite - improved ductility compared to grey cast iron
Special Steels
Maraging Steel - Extremely high strength Steels for High-Temperature Service - for using at high tempearture
Grain Size Refinement
Metals with smaller grains tend to be stronger
Complex-phase Steels
Microstructure of ferrite and bainite with small amount of martensite, retained austenite and pearlite
Dual Phase Steels
Microstructure of ferrite and martensite
Transformation-Induced Plasticity Steels
Microstructure of ferrite, hard martensite or bainite and at least 5% volume of retained austenite
Composite Materials
Non-uniform solid consisting of two or more different materials that are mechanically or metallugically bonded together
Condenstion
Occurs when a polymer is formed plus by-products
Deoxidation
Oxygen reacts with deoxidizers and produce solid metal oxide that are removed from the molten metal or become dispersed throughout the structure
Anisotropic
Properties of laminar composites, distinct layers of materials bonded together
Isotropic
Properties of particulate composite, particles of one material in a matrix of another material
Constructional Alloys
Purchased by AISI-SAE, which effectively specifies chemistry
Quench Media
Quenchants are the medium in which a material is quenched
Alloy Additions
Related to the amounts and types of alloying elements; Primary reason to add an alloying element is to increase hardenability
Non-Coherency (Overage)
Second phase particles have their own crystal structure and distinct interphase boundaries
Ductile or nodular cast iron
Smooth spheroidal graphite - provide ductility
Vacuum Arc Remeltinig (VAR), Vacuum Induction Melting (VIM)
Solidify metal electrode, then metal electrode is remelted, molten droplets pass through a vacuum
Electroslag Remelting (ESR)
Solidify metal electrode, then remelting is conducted under a blanket of molten flux, non metallic, impurities float and are collected in the flux
Free Machine Steels
Steels machine readily and form small chips when cut
Precipitation hardening or Age hardening
Strength is obtained from a nonequilibrium structure
Solid-Solution Strengthening
Substitutional solutions or interstitial solutions
Coherency - A Coherent Precipitate
The crystallographic planes of the parent structure are continuous through the precipitate cluster, and the solute aggregate tends to distort the lattice to a substantial surrounding regiong
Overaging
The decrease in hardness and strength of precipitation or age hardened materials
Jominy Test
The hardenability test - a material is heated and quenched from one end, then hardness along the material length is determined
Carbon Content
The larger carbon content the higher strength, the higher hardness
Continuous Cooling Transformations (CCT)
The modification of ttt diagram, shows the phase and composition of steels upon cooling as functions of temperature and time
Materials Processing
The science and technology that converts a material into a product of a desired shape in the desired quantity
Ausforming
Thermomechanical processes in which deformation and heat treatment are intimately combined. Material is heated to form austenite and then quenched to a temperature between pearlite and bainite; then slowly cooled to produce bainite or rapidly quench to martensite
Heat Treatments for Nonferrous Metals
Three purposes - Produce a uniform, homogenous structure - Provide a stress relief Induce recrystallization
Process of Precipitation Hardening
Three-step Sequence: solution treatment -> quench -> aged
Tempering
To sacrifice strength and hardness for ductility and toughness
Age Hardening
To sacrifice toughness and ductility for strength
Copolymer
Two different types of mer