Materials Science Practice Flashcards

Comprehensive vocabulary flashcards covering the key principles of materials science, including additive manufacturing, polymer physics, metallurgy, and ceramic processing as detailed in the lecture transcripts.

Additive Manufacturing (AM)

A process of building and solidifying in the same step by simultaneously combining material delivery (filament, powder, or paste) and a solidification mechanism (cooling, curing, or sintering).

Thermoplastics

Polymers that soften when heated as secondary bonds weaken, allowing chains to slide; they solidify through cooling which leads to crystallization or a glass-transition.

Thermosets

Polymers that become permanently hard when formed through irreversible covalent cross-linking of monomers triggered by light or heat.

SLA (Stereolithography)

A 2D additive manufacturing process where a laser or projector triggers polymerization in a vat of liquid resin, allowing a whole layer to be cured at once.

Glass

A disordered solid material that has solidified from a liquid without atoms organizing into a repeating periodic crystalline pattern, characterized by only short-range order.

Glass Transition Temperature ($T_g$)

The temperature at which a liquid's viscosity reaches approximately $10^{12}\,Pa\cdot s$, causing molecules to become effectively frozen in place.

Fictive Temperature ($T_f$)

The temperature at which a glass structure was 'frozen in,' capturing the material's memory of its thermal history and cooling rate.

DSC (Differential Scanning Calorimetry)

A technique that measures the heat flow difference between a sample and a reference to identify transitions such as glass transition ($T_g$), crystallization ($T_c$), and melting ($T_m$).

Plasticizer

A small molecule mixed into a polymer to lower its $T_g$ by pushing chains apart, increasing free volume and reducing packing efficiency.

Flory-Fox Equation

A formula describing the $T_g$ of a mixture, given as $\frac{1}{T_{g,mix}} = \frac{\Phi_A}{T_{g,A}} + \frac{\Phi_B}{T_{g,B}}$, where $\Phi$ is the volume fraction.

Inoue Criteria

Rules for forming Bulk Metallic Glasses (BMG) requiring: at least 3 alloying elements, atomic size differences > 12\%, negative mixing enthalpy, and a composition near a eutectic point.

Shear Bands

Localized zones where deformation accumulates in Bulk Metallic Glasses due to the lack of dislocations, often leading to catastrophic sudden fracture.

Network Modifiers

Oxides like $Na_2O$ or $CaO$ added to silicate glass to break $Si-O-Si$ bonds, lowering viscosity and decreasing processing temperatures.

Glass Ceramics

Materials produced by intentionally and controllably crystallizing glass through heat treatment, often resulting in near-zero thermal expansion and high thermal shock resistance.

Electrostatic Valence Rule

Pauling's second rule stating that the bond strength from a cation ($\frac{V_{cation}}{CN}$) must equal the bond strength received by each anion.

Radius Ratio Rule

The ratio of cation to anion radii ($r_c/r_a$) used to predict the coordination number ($CN$) and resulting geometry of ceramic crystal structures.

Frenkel Defect

A point defect in ceramics where a cation moves from its normal lattice site into a nearby interstitial site, creating a cation vacancy and a cation interstitial pair.

Schottky Defect

A point defect involving a paired cation vacancy and anion vacancy to maintain charge neutrality in a ceramic crystal.

Perovskite

A complex ceramic structure with formula $ABO_3$; distortions from its ideal cubic form are responsible for properties like piezoelectricity and ferroelectricity.

Sintering

The consolidation of ceramic powder by heat and/or pressure below the melting point, driven thermodynamically by the reduction of internal surface/interface energy.

Tacticity

The arrangement of side groups along a polymer chain backbone, classified as isotactic (same side), syndiotactic (alternating), or atactic (random).

Spherulite

A spherical semicrystalline domain in polymers consisting of lamellar crystallite ribbons radiating from a center, separated by amorphous material.

Viscoelasticity

A property of materials like polymers that exhibit both elastic (solid-like) and viscous (liquid-like) characteristics depending on time and temperature.

Maxwell Element

A mechanical model for a viscoelastic liquid consisting of a spring and a dashpot in series.

Voigt Element

A mechanical model for a viscoelastic solid consisting of a spring and a dashpot in parallel.

Superplasticizer / Polyolefins

Polymers like PE and PP that are specifically lighter than water because their pure $C-H$ backbone contains no heavy atoms, resulting in densities of $0.90-0.97\,g/cm^3$.

Hall-Petch Equation

A relationship stating that the yield strength of a metal increases as the grain size decreases, expressed as $\sigma_y = \sigma_0 + k d^{-1/2}$.

Orowan Bypassing

A strengthening mechanism in overaged alloys where dislocations bow around large, incoherent precipitates instead of cutting through them.

Fick's First Law

A mathematical description of steady-state diffusion where the flux $J$ is proportional to the concentration gradient: $J = -D \frac{dC}{dx}$.

Kirkendall Effect

Evidence for the vacancy diffusion mechanism in metals where an interface shifts between two different metals due to unequal diffusion rates of the atoms.

Eutectoid Reaction

A solid-state reaction in steel where austenite ($\gamma$) transforms into a mixture of ferrite ($\alpha$) and cementite ($Fe_3C$) at $727^{\circ}C$.

Martensite

A hard, brittle BCT iron phase formed by the diffusionless, athermal transformation of austenite when steel is quenched rapidly.

Hardenability

A material property describing the depth to which a thick metal section can be transformed into martensite upon cooling, often measured by the Jominy end-quench test.

Environmental Stress Cracking (ESC)

Physical degradation where a polymer fails at low stress in the presence of a borderline solvent that plasticizes chains only at the stress concentration zone.

Crazing

A polymer-specific failure stage where a white band forms containing load-bearing fibrils and microvoids that absorb energy before final fracture.

Pilling-Bedworth Ratio (PBR)

The ratio of the volume of a metal oxide to the volume of the metal consumed, used to predict if an oxide layer will be protective ($1-2$), porous ($<1$), or likely to spall ($>2$).

Dislocation Climb

A high-temperature creep mechanism where a dislocation moves out of its slip plane by absorbing or emitting vacancies, allowing it to bypass obstacles.

Anodizing

An electrochemical process used to thicken the natural oxide layer on metals like aluminium to improve corrosion resistance.

Corona Treatment

A surface modification for polymers using an electric discharge to oxidize the surface, introducing polar groups that increase hydrophilicity.