Search Results for precipitate shearing

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, 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 aims to summarize the work on cryogenic strength and toughness and to present the fractography of aluminum alloys. It presents case studies on the importance of understanding the fractography of aluminum alloys and the role of microstructure in the appearance of fractographic features, with variables comprised of in-plane/through-thickness anisotropy, test temperature, heat treatment condition, and the effect of welding.

Fracture of aluminum alloys can occur due to several failure types and/or fracture morphologies, including overload, intergranular fracture, fatigue, corrosion, and mixed-mode fracture. This article provides a detailed discussion on these failure types and/or fracture morphologies. It also presents the differences between wrought and cast aluminum products.

This article discusses fracture, fatigue, and creep of nickel-base superalloys with additional emphasis on directionally solidified and single-crystal applications. It analyzes the physical metallurgy of these alloys. The effects of grain boundary and grain size on failure are summarized. The article also discusses the effects of microstructure and extrinsic parameters on fatigue crack propagation (FCP). It details the modeling of FCP rates and creep and creep-fatigue crack growth rates.

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.

This introductory article provides basic information on the various aspects of solid-state transformation: multiphase microstructures, substructures, and crystallography, which assist in characterizing the morphology of phase transformations. It contains a flowchart that illustrating the classification of transformations by growth processes.

This article describes the general categories and metallurgy of heat treatable aluminum alloys. It briefly reviews the key impurities and each of the principal alloying elements in aluminum alloys, namely, copper, magnesium, manganese, silicon, zinc, iron, lithium, titanium, boron, zirconium, chromium, vanadium, scandium, nickel, tin, and bismuth. The article discusses the secondary phases in aluminum alloys, namely, nonmetallic inclusions, porosity, primary particles, constituent particles, dispersoids, precipitates, grain and dislocation structure, and crystallographic texture. It also discusses the mechanisms used for strengthening aluminum alloys, including solid-solution hardening, grain-size strengthening, work or strain hardening, and precipitation hardening. The process of precipitation hardening involves solution heat treatment, quenching, and subsequent aging of the as-quenched supersaturated solid solution. The article briefly discusses these processes of precipitation hardening. It also reviews precipitation in various alloy systems, including 2xxx, 6xxx, 7xxx, aluminum-lithium, and Al-Mg-Li systems.

This article discusses the microstructural processes that take place during plastic deformation and presents a plain phenomenological and general description of the cyclic stress-strain (CSS) response. It emphasizes the microstructural aspects of cyclic loading on single-phase materials tested in initially soft, dislocation-poor conditions resulting from a prior heat treatment. The article discusses deformation-induced phase transformations in austenitic stainless steels and commercial age-hardened aluminum alloys. It describes the interaction of dislocations and the strengthening of second-phase particles. The article also provides a description of the framework used to model the CSS response on a physical basis.

Martensite is a metastable structure that forms during athermal (nonisothermal) conditions. This article reviews the crystallographic theory, morphologies, orientation relationships, habit plane, and transformation temperature of ferrous martensite microstructures. It examines the stages of the tempering process involved in ferrous martensite. The article also describes the formation of the martensite structure in nonferrous systems. It concludes with a discussion on shape memory alloys.

This article provides a discussion on the transformations of various categories of bainite in ferrous systems. These include upper bainite, lower bainite, inverse bainite, granular bainite, and columnar bainite. The article also provides information on the bainite transformations in nonferrous systems.

Overload failures refer to the ductile or brittle fracture of a material when stresses exceed the load-bearing capacity of a material. This article reviews some mechanistic aspects of ductile and brittle crack propagation, including a discussion on mixed-mode cracking, which may also occur when an overload failure is caused by a combination of ductile and brittle cracking mechanisms. It describes the general aspects of fracture modes and mechanisms. The article discusses some of the material, mechanical, and environmental factors that may be involved in determining the root cause of an overload failure. It also presents examples of thermally and environmentally induced embrittlement effects that can alter the overload fracture behavior of metals.

The cracking process occurs slowly over the service life from various crack growth mechanisms such as fatigue, stress-corrosion cracking, creep, and hydrogen-induced cracking. Each of these mechanisms has certain characteristic features that are used in failure analysis to determine the cause of cracking or crack growth. This article discusses the macroscopic and microscopic basis of understanding and modeling fracture resistance of metals. It describes the four major types of failure modes in engineering alloys, namely, dimpled rupture, ductile striation formation, cleavage or quasicleavage, and intergranular failure. Certain fundamental characteristics of fracture observed in precipitation-hardening alloys, ferrous alloys, titanium alloys are also discussed.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of precipitation-hardening stainless steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the cup-and-cone tension-overload fracture, low-cycle and high-cycle fatigue fracture, fracture surface, brittle intergranular fracture, hydrogen embrittlement, and intergranular stress-corrosion cracking of stainless steel components of these steels. The components include high-pressure compressor parts, springs, deflector yokes of aircraft main landing gears, and aircraft engine mount beams.

This article provides a discussion on forging methods, melting procedures, forging equipment, forging practices, grain refinement, and critical factors considered in forging process. It describes the different types of solid-solution-strengthened and precipitation-strengthened superalloys, namely, iron-nickel superalloys, nickel-base alloys, cobalt-base alloys, and powder alloys. The article discusses the microstructural mechanisms during hot deformation and presents processing maps for various superalloys. It concludes with a discussion on heat treatment of wrought heat-resistant alloy forgings.

Maraging steels are highly alloyed low-carbon iron-nickel martensite steels that possess an excellent combination of strength and toughness superior to that of most carbon-hardened steels. This article provides a detailed account of the formation of martensite in maraging steels. It discusses the heat treatment of these steels, namely, aging, solution annealing, age hardening, and nitriding. Their hardening during aging has been attributed to two different mechanisms: short-range ordering and precipitation. The article concludes with a discussion on the grain refinement using thermal cycling and transformation-induced plasticity maraging methods.