Inglês para Ciência dos Materiais: Vocabulário Essencial

"unit cell"

The smallest repeating structural unit of a crystal lattice that defines the geometry of the entire crystal

"The face-centred cubic unit cell of copper contains four atoms and has a lattice parameter of 3.61 Å."

"grain boundary"

The interface between two adjacent crystalline grains of different orientations within a polycrystalline material

"Segregation of impurities at grain boundaries weakened the alloy and promoted intergranular fracture."

"dislocation"

A linear crystal defect representing a misalignment of atoms that allows plastic deformation at stresses far below the theoretical strength

"The high dislocation density introduced by cold working raised the yield strength of the steel significantly."

"covalent bonding"

A type of interatomic bonding in which electrons are shared between atoms, producing directional bonds of high strength

"The covalent bonding in diamond accounts for its exceptional hardness and electrical insulating behaviour."

"lattice parameter"

The length of an edge of the unit cell, used to characterise the dimensions of a crystal structure

"X-ray diffraction measured a lattice parameter of 4.05 Å for the aluminium specimen, consistent with published values."

"point defect"

A localised imperfection in a crystal lattice involving a single atomic site, such as a vacancy or interstitial atom

"Vacancy concentration increases exponentially with temperature, influencing diffusion rates in the solid."

"solid solution"

A homogeneous crystalline phase in which one element is dissolved within the lattice of another, either substitutionally or interstitially

"Carbon dissolves interstitially in iron to form a solid solution that is essential to steel strengthening."

"amorphous"

Describing a material that lacks long-range atomic order, instead possessing a disordered, glass-like structure

"Amorphous silicon films are deposited by chemical vapour deposition for thin-film solar cell applications."

"yield strength"

The stress at which a material begins to deform plastically and no longer returns to its original shape when the load is removed

"The 0.2% offset yield strength of the titanium alloy was 880 MPa, well above the design requirement."

"fracture toughness"

A measure of a material's ability to resist crack propagation when a stress is applied, expressed as a critical stress intensity factor

"The fracture toughness of zirconia-toughened ceramics is an order of magnitude higher than that of pure alumina."

"fatigue"

The progressive, localised damage that accumulates in a material subjected to cyclic loading, eventually leading to crack initiation and failure

"Fatigue cracks initiated at surface machining marks and propagated to failure after 10⁷ loading cycles."

"creep"

The time-dependent plastic deformation of a material under constant stress at elevated temperature

"Creep tests at 950°C showed that the nickel superalloy maintained acceptable strain rates for turbine blade applications."

"hardness"

A material's resistance to localised plastic deformation, typically measured by the depth or area of an indentation produced by a standard indenter

"Vickers hardness measurements across the heat-affected zone revealed a significant drop in hardness adjacent to the weld."

"elastic modulus"

The ratio of stress to strain within the elastic region of a material's behaviour, quantifying its stiffness

"The elastic modulus of carbon fibre reinforced polymer along the fibre direction reached 150 GPa, six times that of aluminium."

"ductility"

The ability of a material to undergo significant plastic deformation before fracture, often expressed as percentage elongation or reduction in area

"The low ductility of cast iron, typically below 1%, makes it unsuitable for applications where impact resistance is required."

"strain hardening"

The increase in hardness and yield strength of a metal that occurs when it is plastically deformed below its recrystallisation temperature

"The sheet metal underwent strain hardening during deep drawing, requiring an intermediate annealing step to restore ductility."

"annealing"

A heat treatment process in which a material is heated to a high temperature and slowly cooled to relieve internal stresses and restore ductility

"Full annealing at 850°C followed by furnace cooling reduced the hardness of the cold-worked steel to a machinable level."

"quenching"

Rapid cooling of a heated material, typically in water or oil, to suppress equilibrium phase transformations and retain a metastable microstructure

"Quenching from the austenitising temperature produced a martensitic microstructure with hardness exceeding 60 HRC."

"sintering"

The consolidation of a powder compact into a dense solid by heating below the melting point, driven by diffusion and surface energy reduction

"Spark plasma sintering of tungsten carbide powder at 1400°C produced a near-full-density cutting tool insert."

"precipitation hardening"

A heat treatment sequence that produces fine second-phase particles within a matrix, impeding dislocation motion and substantially increasing strength

"Precipitation hardening of aluminium 7075 through solution treatment, quench, and ageing raised tensile strength to 570 MPa."

"recrystallisation"

The formation of new strain-free grains within a deformed metal upon heating, eliminating the work-hardened microstructure

"Recrystallisation began at approximately 400°C in the cold-rolled copper strip, restoring full ductility after 30 minutes."

"casting"

A manufacturing process in which molten material is poured into a mould and allowed to solidify in the desired shape

"Investment casting of the turbine blade achieved wall thicknesses below 1 mm with dimensional tolerances of ±0.1 mm."

"tempering"

A heat treatment applied to hardened steel by reheating below the critical temperature to reduce brittleness while retaining most of the hardness

"Tempering at 200°C transformed the brittle as-quenched martensite into tempered martensite with improved toughness."

"diffusion bonding"

A solid-state joining process in which intimate contact at elevated temperature and pressure allows atoms to diffuse across the interface, forming a strong bond

"Diffusion bonding of titanium components eliminated the need for brazing filler metal and produced a joint of parent-metal strength."

"superalloy"

A high-performance metallic alloy based on nickel, cobalt, or iron that retains high strength and oxidation resistance at extreme temperatures

"The turbine disc was machined from a nickel-base superalloy capable of operating continuously at 1050°C."

"thermoplastic"

A polymer that softens on heating and hardens on cooling in a repeatable and reversible manner, allowing reprocessing

"The thermoplastic polyamide component was injection-moulded at 280°C and could be recycled at end of life."

"thermoset"

A polymer that irreversibly cross-links during curing, forming a three-dimensional network that cannot be remelted

"The epoxy thermoset matrix of the composite panel cured at 120°C for two hours, achieving full mechanical properties."

"composite"

An engineered material made of two or more constituent materials with significantly different properties that, when combined, produce characteristics superior to the individual components

"Carbon fibre reinforced polymer composites reduced the airframe weight by 20% compared with an equivalent aluminium structure."

"ceramic"

An inorganic, non-metallic material that is typically hard, brittle, and resistant to heat and chemical attack, often having ionic or covalent bonding

"Alumina ceramics are used for cutting tool inserts due to their high hardness, chemical inertness, and thermal stability."

"semiconductor"

A material with electrical conductivity between that of a conductor and an insulator, whose conductivity can be controlled by doping or applied fields

"Silicon remains the dominant semiconductor material for integrated circuits, with band gap of 1.12 eV at room temperature."

"smart material"

A material that changes a physical property in response to an external stimulus such as temperature, stress, electric field, or magnetic field

"Shape memory alloy actuators made from nitinol exploit the smart material's ability to recover deformation on heating."

"biomaterial"

A material intended to interface with biological systems for medical purposes, designed to be biocompatible with living tissue

"The hydroxyapatite-coated titanium implant demonstrated excellent osseointegration as a biomaterial for orthopaedic applications."

"X-ray diffraction"

An analytical technique that directs X-rays at a crystalline sample and measures the diffracted intensities to determine crystal structure and phase composition

"X-ray diffraction confirmed the presence of a retained austenite phase in the heat-treated bearing steel."

"scanning electron microscopy"

A microscopy technique that scans a focused electron beam over a sample surface to produce high-resolution images of morphology and topography

"Scanning electron microscopy of the fracture surface revealed fatigue striations indicating crack growth per cycle."

"transmission electron microscopy"

A technique in which electrons are transmitted through an ultra-thin specimen to reveal atomic-scale structure, defects, and phases

"Transmission electron microscopy showed coherent precipitates of approximately 5 nm diameter distributed uniformly in the matrix."

"energy dispersive spectroscopy"

An elemental analysis technique coupled to an electron microscope that identifies elements by the characteristic X-rays they emit under electron bombardment

"Energy dispersive spectroscopy mapped the chromium depletion zone adjacent to the grain boundary in the sensitised stainless steel."

"thermogravimetric analysis"

A thermal analysis method that measures changes in a sample's mass as a function of temperature or time under a controlled atmosphere

"Thermogravimetric analysis quantified the moisture content and decomposition temperature of the polymer resin."

"nanoindentation"

A technique for measuring hardness and elastic modulus at the nanoscale by pressing a sharp indenter into a sample surface and recording the load-displacement response

"Nanoindentation across the diffusion zone revealed a gradient in hardness corresponding to changes in local composition."

"differential scanning calorimetry"

A thermal analysis technique that measures the heat flow to and from a sample compared with a reference as both are subjected to a controlled temperature programme

"Differential scanning calorimetry identified the glass transition temperature of the polymer at 145°C and quantified crystallinity."

"atom probe tomography"

An atomic-resolution technique that field-evaporates individual atoms from a sharp needle specimen and uses time-of-flight mass spectrometry to map their three-dimensional elemental distribution

"Atom probe tomography revealed solute clustering at grain boundaries at concentrations below the detection limit of conventional SEM."

"galvanic corrosion"

Accelerated corrosion of the less noble metal that occurs when two dissimilar metals are in electrical contact in an electrolyte

"Galvanic corrosion caused rapid wastage of the aluminium fittings bolted directly to the carbon fibre composite panel."

"passivation"

The formation of a thin, adherent oxide film on a metal surface that acts as a barrier to further corrosion

"Stainless steel relies on passivation by a chromium-rich oxide layer to maintain its corrosion resistance in aggressive environments."

"stress corrosion cracking"

A form of environmentally assisted cracking in which a susceptible material fractures under the combined action of tensile stress and a specific corrosive environment

"Stress corrosion cracking caused failure of the high-strength steel bolts immersed in a chloride-containing solution under sustained load."

"pitting"

A localised form of corrosion in which small pits or cavities form on the metal surface due to breakdown of the passive film at specific sites

"Pitting of the 316L stainless steel vessel was initiated by chloride ions at surface inclusions above the pitting potential."

"oxidation"

The chemical reaction of a material with oxygen, typically at elevated temperature, leading to the formation of an oxide scale on the surface

"At 1000°C, the uncoated bond coat alloy showed severe oxidation and spallation of the thermally grown oxide after 100 hours."

"hydrogen embrittlement"

A loss of ductility and fracture toughness in a metal caused by the absorption and diffusion of atomic hydrogen into the microstructure

"Hydrogen embrittlement during electroplating caused delayed fracture of the high-strength fasteners at stresses well below yield."

"intergranular corrosion"

Preferential corrosion along or immediately adjacent to grain boundaries while the bulk of the grains remains largely unattacked

"Sensitisation during welding led to intergranular corrosion of the austenitic stainless steel in the heat-affected zone."

"cathodic protection"

A technique for reducing corrosion of a metal surface by making it the cathode of an electrochemical cell, either with a sacrificial anode or an impressed current

"An impressed current cathodic protection system was installed to protect the buried pipeline from soil corrosion."