Term
|
Definition
| strengthening mechanism relying on a series of solid state solution transformations. Generates ultra fine particles of a second phase. Form of dispersion hardening |
|
|
Term
|
Definition
1. solution treatment
2. quench
3. Age |
|
|
Term
| what is solution treatment? |
|
Definition
| heat between solvus temperature and eutectic temperature to form homogeneous single phase. Stay below eutectic temp to avoid hot-shortness (melting of non-equilibrium eutectic microconstituent) |
|
|
Term
| purpose of quenching in age hardening? |
|
Definition
| to create super-saturated solid solution |
|
|
Term
| What does aging do in age hardening? What temperature should you use? |
|
Definition
| age hardening allows short-range dispersion of the super solute to form ultra fine second phase with uniform dispersion. Ideal temp? below the solvus temperature. you want to have enough activation energy to facilitate diffussion, but not enough to encourage grain growth. Nucleation should be prioritized |
|
|
Term
| requirements for age hardening? |
|
Definition
1. must display decreasing solid solubility with decreasing temperature--enter a one phase region on heating and two-phase region on cooling
2. matrix should be soft and ductile. precipitate should be hard and brittle. Often an intermetallic compound.
3. Must be quenchable-in other words, must be able to cool it fast enough to suppress the formation of the precipitate.
4. A coherent precipitate must form |
|
|
Term
|
Definition
| has a definite relationship with the matrix's crystal structure |
|
|
Term
|
Definition
| a single phase liquid solidifies to a two phase solid |
|
|
Term
|
Definition
| lowest melting temperature. eutectic composition melts first as metal is heated. |
|
|
Term
|
Definition
| single phase solid cools to become two-phase solid |
|
|
Term
|
Definition
| fraction=(length other side/total length) |
|
|
Term
|
Definition
| the boundary between the two or more phases impedes the movement of dislocations and improves strength |
|
|
Term
| best dispersion strengthening? |
|
Definition
| many, small, round, hard, and discontinuous dispersed particles that are hard in a ductile matrix--obstacles to dislocations |
|
|
Term
|
Definition
| often brittle compounds that act a lot like ceramics. often have stoichiometric composition. make great dispersed phase |
|
|
Term
| eutectic microconstituent |
|
Definition
| mixture of two phases form as a result of the eutectic rxn. lowest melting point microconstituent |
|
|
Term
|
Definition
| spacing between the center of a plate with one composition to the center of an adjacent layer with the same composition |
|
|
Term
|
Definition
| surface between two in a microstructure that resists dislocation motion and provides dispersion strengthening and precipitation hardening |
|
|
Term
| another name for age hardening? |
|
Definition
|
|
Term
|
Definition
| solubility curve that separates a single solid phase from a two- solid phase region in a phase diagram |
|
|
Term
|
Definition
| reheating solution treated and quenched alloy to speed up the formation of the precipitate |
|
|
Term
|
Definition
| depends only on the temperature and not on the time |
|
|
Term
|
Definition
| FCC iron and iron-carbon alloys (gamma iron) |
|
|
Term
|
Definition
| describes the fraction of a transformation that occurs as a function of time. For diffusion based transformations |
|
|
Term
| what are the implications of the martensitic transformation being athermal |
|
Definition
| if cooling to m_s is achieved with austenite present, there will be a martensite microconstituent present |
|
|
Term
|
Definition
| 2-phase microconstituent consisting of ferrite+cementite. transformation occurs at temp below the nose on TTT and CCT diagrams |
|
|
Term
|
Definition
| steels that can be age-hardened at low temperatures |
|
|
Term
|
Definition
| Fe3C hard, brittle, provides strengthening in steels with proper dispersion |
|
|
Term
| displacive transformations |
|
Definition
| transformation that involves only a small displacement of atoms or ions. NOT diffusion. Martensitic rxn relies on this. This is an ATHERMAL process |
|
|
Term
|
Definition
| BCC iron α and δ excludes ceramic ferrites |
|
|
Term
|
Definition
| the energy associated with the boundary between two phases |
|
|
Term
| isothermal transformation |
|
Definition
| transformation that occurs at constant temperature-takes time |
|
|
Term
|
Definition
| a metastable phase formed in still by athermal transformation. BCT structure. hard, hardenable, brittle |
|
|
Term
| martensitic transformation |
|
Definition
|
|
Term
|
Definition
| precipitate hardening that occurs without baking. the diffusion takes longer without added (artificial) thermal energy ~ambient temperatures |
|
|
Term
|
Definition
| two phase lamellar microconstituent of ferrite and cementite. Forms under normal cooling or isothermally transformed at relatively high temperatures |
|
|
Term
|
Definition
| the energy required to permit a precipitate to fit in the surrounding matrix during nucleation and growth of the precipitate |
|
|
Term
| supersaturated solid solution |
|
Definition
| the solid solution formed when a material is rapidly cooled from a high T, single phase to a two phase region without the second phase precipitating. |
|
|
Term
|
Definition
| a heat treatment to increase the toughness of martensite. It permits the martensite to begin to decompose into the equilibrium phases α and cementite |
|
|
Term
|
Definition
| furnace cooling to produce a ferrite matrix via austenite transformation |
|
|
Term
|
Definition
| austentize, then furnace cool to produce soft, course pearlite |
|
|
Term
|
Definition
| plastic deformation of austentite below A1 temperature. Then permit transform to to bainite or martensite. Facilitated in a some alloys by 'bay' in the TTT diagram |
|
|
Term
|
Definition
| the isothermal heat treatment by which austenite transforms to bainite |
|
|
Term
|
Definition
| 1st step in most heat treatments for steel or cast iron. heat to form homogeneous austenite |
|
|
Term
|
Definition
|
|
Term
|
Definition
| like carburizing, but with nitrogen in the gas as well |
|
|
Term
|
Definition
| the depth below the surface that shows effects of case hardening and carburizing processes |
|
|
Term
|
Definition
| ferrous alloys containing enough C that the eutectic rxn occurs during solidification |
|
|
Term
| compacted graphite cast iron |
|
Definition
| cast iron with small amounts of Mg and Ti to make the carbon form a coral shaped precipitate during solidification. Properties are between gray and ductile iron |
|
|
Term
|
Definition
| surface hardening by means of a cyanide bath treatement |
|
|
Term
|
Definition
| reheating an malleable iron to reduce the amount of carbon combined as cemementite by spheroidizing pearlite, temperizing martensite, or both |
|
|
Term
|
Definition
| specialty steels treated to produce martensite dispersed in a ferrite matrix |
|
|
Term
|
Definition
| cast iron treated with magnesium to cause graphite to precipitate to spheroids during solidification, permitting excellent strength and ductility |
|
|
Term
|
Definition
| class of stainless steels containing microstructure of ferrite and austenite |
|
|
Term
|
Definition
| furnace used to melt scrap steel. often used to create specialty steel |
|
|
Term
|
Definition
| a cluster of graphite flakes produced during the solidification of grey iron that are interconnected to a common nucleus |
|
|
Term
|
Definition
| the loss of nodulizing or inoculating effects in cast irons as a function of time, permitting undesireable changes in microstructure and properties |
|
|
Term
| first stage graphitization |
|
Definition
| the first step in heat treatment of malleable cast iron, during which the carbides formed during solidification are decomposed to graphite and austenite |
|
|
Term
|
Definition
| cast iron which contains graphite flakes. low strength, poor ductility. most widely used type of cast iron |
|
|
Term
|
Definition
| the ease with which a steel can be quenched to form martensite. steels with high hardenability form martensite even with slow cooling |
|
|
Term
|
Definition
| graphs showing the effect of cooling rate on the hardness of as-quenched steel |
|
|
Term
|
Definition
| the molten iron produced in a blast furnace- contains about 95% iron, 4% carbon, 0.3-0.9% Si, 0.5% Manganese, and 0.025-0.05% each of sulfur, phosphorous and titanium |
|
|
Term
|
Definition
| the addition of an agent to molten cast iron that provides nucleation sites at which graphite precipitates during solidification |
|
|
Term
|
Definition
| steels containing Nb and Ti. They react to C and S to form precipitates of carbides and sulfides, leaving the ferrite nearly free of interstitial elements. |
|
|
Term
|
Definition
| heat treatment of steel by austentizing, cooling rapidly to a temperature between A1, and the nose of the TTT curve and holding until the austenite transforms to pearlite |
|
|
Term
|
Definition
| the distance from the quenched end of a jominy bar. the jominy distance is related to the cooling rate |
|
|
Term
|
Definition
| the test used to evaluate hardenability. an austentized steel bar is quenched at one end only, creating a range of cooling rates along the bar |
|
|
Term
|
Definition
| cast iron obtained by lengthy heat treatment, during which cementite decomposes to produce rounded clumps of graphite. good strength, ductility, and toughness result |
|
|
Term
|
Definition
| a special class of steels that obtain high strength through martensitic and age hardening rxns |
|
|
Term
|
Definition
| quenching austentinzed steel to a temp just above Ms and holding until the temperature is the same throughout before further cooling to reduces thermal stresses due and quench cracking |
|
|
Term
|
Definition
| case hardening using nitrogen diffusion |
|
|
Term
|
Definition
| the addition of magnesium to molten cast iron to cause graphite to precipitate as spheres rather than flakes during solidification |
|
|
Term
|
Definition
| heat treatment by austentizing and then air cooling to produce a fine pearlitic structure. works for steels and cast irons |
|
|
Term
|
Definition
|
|
Term
|
Definition
| low temp heat treatment used to remove some or all of the effect of cold work |
|
|
Term
|
Definition
| cracks that form as a result of stresses due to the volume change that accompanies the austenite to martensite transformation |
|
|
Term
|
Definition
| austenite that is unable to convert to martensite during quenching because of the volume expansion associated with the rxn |
|
|
Term
| second stage graphitization |
|
Definition
| second step in the heat treatment of malleable irons that havea ferritic matrix. the iron is cooled slowly from the first stage graphitization so taht austenite transforms to ferrite and graphite rather than pearlite |
|
|
Term
|
Definition
| unusually high hardness in a steel tempered at high temperature by the precipitation of alloy carbides |
|
|
Term
|
Definition
| when heated to ~480-860C chromium carbides precipitate along grain boundaries causing a chromium depleted interior. Causes stainless steels to corrode very easily |
|
|
Term
|
Definition
| a microconstituent containing course spherical cementite particles in matrix of ferrite in high carbon steels, permitting great machinability |
|
|
Term
|
Definition
| a group of ferrous alloys that contain at least 11%Cr, providing extraordinary corrosion resistance |
|
|
Term
|
Definition
| the microconstituent of ferrite and cementite that is formed when martensite is tempered |
|
|
Term
|
Definition
| a group of high carbon steels that provide combinations of high hardness, toughness and resistance to high temperatures |
|
|
Term
|
Definition
| a group of steels with a microstructure that consists of a continuous ferrite matrix, a harder second phase( martensite and or bainite), and retained austenite. TRIP stands for transformation induced plasticity |
|
|
Term
|
Definition
| the rounded, interconnected graphite that forms during the solidification of cast iron. This is the intended shape in compacted graphite iron, but is a defective shape in ductile iron |
|
|
Term
|
Definition
| cast iron that produces cementite rather than graphite during solidification. the white irons are hard and brittle |
|
|
Term
| what is the difference between white and grey iron? |
|
Definition
| white cast iron forms cementite rather than graphite during solidification. |
|
|
