Search Results for strengthening mechanisms

The physical and mechanical properties of aluminum alloy can be improved by strengthening mechanisms such as strain hardening used for non-heat treatable aluminum alloy and precipitation hardening used for heat treatable aluminum alloy. This article focuses on the effect of strengthening mechanisms on the physical and mechanical properties of non-heat treatable and heat treatable aluminum alloys. It describes the use of the aluminum alloy phase diagram in determining the melting temperature, solidification path, equilibrium phases, and explains the effect of alloying element in phase formation.

A computational tool would require the contribution of the strengthening mechanisms of metallic material to be predicted and then summed in an appropriate way to derive an estimate of the tensile properties. This article focuses on the modeling of deformation mechanisms pertinent to structural materials, namely, solid-solution strengthening, age/precipitation hardening, dispersion strengthening, grain size reduction, strengthening from cold work, and strengthening from interfaces. It explains the application of predictive models in the atomistic modeling of dislocation structures and cast aluminum property prediction. The article concludes with information on the use of rules-based approaches and data-mining techniques for quantitative predictions of tensile properties.

This article reviews the fundamental relationships between microstructure and mechanical properties for major classes of nonmetallic engineering materials: metals, ceramics and glasses, intermetallic compounds, polymers, and composites. It details the structures of inorganic crystalline solids, inorganic noncrystalline solids, and polymers. The article describes the various strengthening mechanisms of crystalline solids, namely, work hardening, solid-solution hardening, particle/precipitation hardening, and grain size hardening. Deformation and strengthening of composite materials, polymers, and glasses are reviewed. The article concludes with information on the two important aspects of the mechanical behavior of any class of engineering material: fatigue response and fracture resistance.

Heat treatment simulation helps to predict heat treatment results such as component microstructures, properties, residual stresses, and distortion, and thereby assists in reducing experimental effort in defining heat treatment parameters. This article discusses the modeling and simulation of age hardening as being the most important heat treatment to strengthen aluminum alloys. It provides information on the heat treatment simulation model, the yield strength model based on the responsible strengthening mechanisms, and the flow curve model based on mechanical tests. The article also discusses simulation of the quenching process, and provides examples for aluminum quenching simulation.

This article provides information on the Unified Numbering System designations and temper designations of copper and copper alloys. It discusses the basic types of heat treating processes of copper and copper alloys, namely, homogenizing, annealing, and stress relieving, and hardening treatments such as precipitation hardening, spinodal hardening, order hardening, and quench hardening and tempering. The article presents tables that list the compositions and mechanical properties of copper alloys. It also discusses two strengthening mechanisms of copper alloys, solid-solution strengthening and work hardening. Finally, the article provides information on the equipment used for the heat treating of copper and copper alloys, including batch-type atmosphere furnaces, continuous atmosphere furnaces, and salt baths.

This article begins by describing the designations of cast and wrought aluminum alloys. It explains the effects of main alloying elements in aluminum alloys: boron, chromium, copper, iron, lithium, magnesium, manganese, nickel, phosphorus, silicon, sodium, strontium, titanium, and zinc. The article describes the microstructure of cast and wrought aluminum alloys and the various strengthening mechanisms, including solid solution, grain refinement, strain or work hardening, precipitation (or age) hardening, and dispersoid strengthening. The article explicates the tribological behavior of aluminum alloys, aluminum-base composites, and metal-matrix composites. It presents the effect of material-related parameters and external factors on wear behavior and transitions of aluminum-silicon alloys. The article also presents the most important factors affecting the dry sliding wear behavior of particle-reinforced aluminum-base composites against a steel counterface.

This article, to develop an understanding of the underlying mechanisms governing deformation at elevated temperatures, discusses the phenomenological effects resulting from temperature-induced thermodynamic and kinetic changes. It describes the deformation behavior of engineering materials using expressions known as constitutive equations that relate the dependence of stress, temperature, and microstructure on deformation. The article reviews the characteristics of creep deformation and mechanisms of creep, such as power-law creep, low temperature creep, power-law breakdown, diffusional creep, twinning during creep deformation, and deformation mechanism maps. It discusses the creep-strengthening mechanisms for most structural engineering components. The article provides a description of the microstructural modeling of creep in engineering alloys.

This article discusses some elevated-temperature properties of carbon steels and low-alloy steels with ferrite-pearlite and ferrite-bainite microstructures for use in boiler tubes, pressure vessels, and steam turbines. The selection of steels to be used at elevated temperatures generally involves compromise between the higher efficiencies obtained at higher operating temperatures and the cost of equipment, including materials, fabrication, replacement, and downtime costs. The article considers the low-alloy steels which are the creep-resistant steels with 0.5 to 1.0% Mo combined with 0.5 to 9.0% Cr and perhaps other carbide formers. The factors affecting mechanical properties of steels include the nature of strengthening mechanisms, the microstructure, the heat treatment, and the alloy composition. The article describes these factors, with particular emphasis on chromium-molybdenum steels used for elevated-temperature service. Although the mechanical properties establish the allowable design-stress levels, corrosion effects at elevated temperatures often set the maximum allowable service temperature of an alloy. The article also discusses the effects of alloying elements in annealed, normalized and tempered, and quenched and tempered steels.

This article reviews the concepts considered important for an understanding of the processes used for preparing cobalt-chromium alloy implants, the microstructures resulting from this processing, and the resulting material properties. The review includes solidification of alloys, diffusionless (martensitic) phase transformation as occurs with face-centered cubic to hexagonal close-packed transformation in cobalt-chromium alloys, and stacking faults and twins and their role in this transformation. It also discusses the strengthening mechanisms that are responsible for the mechanical properties of cast and wrought cobalt alloys. The article contains tables that list the commonly used cobalt alloys and their biomedical applications and chemical compositions. It discusses the mechanical and corrosion properties of cobalt alloys, and provides a description of the microstructure of cobalt alloys.

Aluminum mill products are those that have been subjected to plastic deformation by hot- and cold-working mill processes such as rolling, extruding, and drawing, either singly or in combination. Microstructural changes associated with the working and with any accompanying thermal treatments are used to control certain properties and characteristics of the worked, or wrought, product or alloy. This article discusses the designation system, classification, product forms, corrosion and fabrication characteristics, and applications of wrought aluminum alloys. Commercial wrought aluminum products are divided into flat-rolled products (sheet, plate, and foil); rod, bar, and wire; tubular products; shapes; and forgings. The article discusses factors affecting the strengthening mechanisms, fracture toughness, and physical properties of aluminum alloys, in addition to the effects of alloying on the physical and mechanical properties. Important alloying elements and impurities are listed alphabetically as a concise review of major effects.

This article describes the development of heat-resistant titanium-base alloys and their classification into several microstructure categories based on their strengthening mechanisms. It explains the phase transformation in titanium-aluminum-base alloys and two peritectic reactions that take place in the titanium-aluminum system. The article also describes two approaches for controlling the orientation of the high-temperature alpha phase to achieve the required lamellar orientation by directional solidification in order to improve the strength and ductility of titanium-aluminum alloys. One approach is by seeding the alpha phase in the alloys, and the other is without seeding, by controlling the solidification path of alloys through appropriate alloying. The article discusses the grain refinement technique used to improve the ductility of cast titanium-aluminum alloys to a level of above 1" at room temperature and reasonable room temperature ductility in the as-cast condition. Finally, it provides information on the microstructures produced through various near-net shape manufacturing processes.

Cast nickel-base alloys are used extensively in corrosive-media and high-temperature applications. This article briefly reviews the common types of heat treatments of nickel alloy castings: homogenization, stress relieving, in-process annealing, full annealing, solution annealing, quenching, coating diffusion, and precipitation. It describes the three general strengthening mechanisms, namely, solid-solution hardening, age hardening, and carbide precipitation. The article summarizes the typical heat treatment of the general families of nickel-base castings used in industrial applications. It focuses on the solution treatment and age hardening of cast nickel-base superalloys and the heat treatment of cast solid-solution alloys for corrosion-resisting applications. The article also discusses the typical types of atmospheres used in annealing or solution treating: exothermic, endothermic, dry hydrogen, dry argon, and vacuum.

This article discusses the bulk formability or workability of steels. It describes their formability characteristics and presents procedures for various formability tests used for carbon and alloy steels. Tests for bulk formability can be divided into two main categories: primary tests and specialized tests. The article compares the processing of microalloyed plate and bar products. The article focuses on the use of torsion testing to evaluate the forgeability of carbon and alloy steels and presents information on measuring flow stress. The article discusses the metallurgy and thermomechanical processing of high-strength low-alloy (microalloyed) steels and the various parts of the rolling operation. The article summarizes some of the common tests for determining formability in open-die and closed-die forgings.

Oxide dispersion-strengthened (ODS) alloys are produced by mechanical alloying, a process by which base metals and alloying particles are powdered together forming a metal-matrix composite. This article discusses the production of ODS superalloy powders and subsequent processing steps, including consolidation, hot rolling, heat treating, and the fabrication of mill products. It also discusses the nominal composition and microstructure of commercial ODS alloys, including nickel, iron, and aluminum-base systems, and provides detailed information on their mechanical, physical, oxidation, and hot-corrosion properties.

This article covers the current state of materials development of nickel-base superalloys for additive manufacturing (AM) processes and the associated challenges. The discussion focuses on nickel-base superalloy fusion AM processes, providing information on typically encountered cracking mechanisms in AM nickel-base superalloys, such as solid-solution-strengthened nickel-base superalloys and precipitate-strengthened nickel-base superalloys. The mechanisms include solidification cracking, strain-age cracking, liquation cracking, and ductility-dip cracking. The article also provides a short discussion on binder jet AM and powder recyclability.