Search Results for strain-age embrittlement

This article examines the embrittlement of iron and carbon steels. It describes compositional, processing, and service conditions that contribute to the problem and presents examples of how embrittlement influences mechanical properties. Embrittlement due to hydrogen is the most common form of embrittlement and influences the behavior and properties of nearly all ferrous alloys and many metals. The article explains why hydrogen embrittlement is so widespread and reviews the many types of damage it can cause. It also explores other forms of embrittlement, including metal-induced embrittlement, strain-age and aluminum nitride embrittlement, thermal embrittlement, quench cracking, 475 deg C and sigma phase embrittlement (in FeCr alloys), temper embrittlement, and embrittlement caused by neutron irradiation. In addition, the article covers stress-corrosion cracking along with properties and conditions that affect it, and the procedures to detect and evaluate it.

This article aims to identify and illustrate the types of overload failures, which are categorized as failures due to insufficient material strength and underdesign, failures due to stress concentration and material defects, and failures due to material alteration. It describes the general aspects of fracture modes and mechanisms. The article briefly reviews some mechanistic aspects of ductile and brittle crack propagation, including discussion on mixed-mode cracking. Factors associated with overload failures are discussed, and, where appropriate, preventive steps for reducing the likelihood of overload fractures are included. The article focuses primarily on the contribution of embrittlement to overload failure. The embrittling phenomena are described and differentiated by their causes, effects, and remedial methods, so that failure characteristics can be directly compared during practical failure investigation. The article describes the effects of mechanical loading on a part in service and provides information on laboratory fracture examination.

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.

Identification of the fracture mechanism is one of the principal responsibilities of a failure analyst and is an important component of any root-cause analysis. This article explores the varied mechanisms responsible for metal fracture, particularly regarding fractography. The behavior of engineering materials at fracture is based on a large number of interrelated characteristics from the atomic level to the component level. These characteristics range from ductile to brittle at the microscale and macroscale levels. Fundamental relative ductility results from the type of electronic bonding, the crystal structure, and the broader long-range degree of order. It provides detailed discussion on ductile fracture, brittle fracture, mixed fracture, embrittlement, stress-corrosion cracking.

In this article, a basic summary of fracture mechanisms in carbon and alloy steels is presented, along with numerous examples of these fractures. These examples include ductile fracture, brittle cleavage fracture, intergranular fracture, fatigue fracture, and environmentally assisted failure mechanisms.

Wear of metals occurs by plastic displacement of surface and near-surface material, and by detachment of particles that form wear debris. This article presents a table that contains the classification of wear. It describes the testing and evaluation of wear and talks about the abrasive wear, lubrication and lubricated wear, and selection of steels for wear resistance. The article discusses the effect of alloying elements, composition, and mechanical properties of carbon and low-alloy steels at elevated temperatures. It talks about the fatigue resistance characteristics of steels, and describes the forms of embrittlement associated with carbon and low-alloy steels. The article provides information on the effect of composition, manufacturing practices, and microstructure on notch toughness of steels. Finally, it explains the effects of alloy elements, inclusion content, microstructure and heat treatment on fracture toughness of steels.

This article is a comprehensive collection of terms related to corrosion fundamentals, testing, and protection.

Hydrogen damage is a form of environmentally assisted failure that results from the combined action of hydrogen and residual or applied tensile stress. This article classifies the various forms of hydrogen damage and summarizes the theories that seek to explain these types of degradation. It reviews hydrogen degradation in specific ferrous and nonferrous alloys, namely, iron-base alloys, nickel alloys, aluminum alloys, copper alloys, titanium alloys, zirconium alloys, and vanadium, niobium, tantalum, and their alloys. An outline of hydrogen damage in intermetallic compounds is also provided.

This article focuses on the fractography of Nitinol, a shape memory alloy of nickel and titanium, in superelastic biomedical applications, which primarily comprise drawn and/or laser-cut wire and tube components. Overload fracture, hydrogen embrittlement fracture, and fatigue fracture are discussed in detail.

This article summarizes the metallurgy of carbon and alloy steels, followed by discussions on their major mechanical properties, namely, static fracture toughness, dynamic fracture toughness, fatigue or sustained-load crack growth rates, and fatigue or sustained-load thresholds. It addresses fatigue crack propagation and sustained-load crack propagation, as well as the fundamental aspects of fracture in steels. The article illustrates the effects of variations in the alloy chemistry, microstructure, temperature, strain rate, and environment on various fracture toughness or crack growth rate parameters.

This article discusses the various options for controlling fatigue and fractures in welded steel structures, with illustrations. It describes the factors that influence them the most. The article details some of the leading codes and standards for designing against failure mechanisms. Codes are presented for fitness-for-service and standards for fatigue and fracture control.

This article begins with a discussion on the classification of hydrogen embrittlement and likely sources of hydrogen and stress. The article describes several hydrogen embrittlement test methods, including cantilever beam tests, wedge-opening load tests, contoured double-cantilever beam tests, rising step-load tests, and slow strain rate tensile tests. It also describes the interpretation of test results and how to control hydrogen embrittlement during production.

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 emphasizes short-term tension and compression testing of metals at high temperatures. It describes the effect of temperature on deformation and strain hardening, occurrence of high-temperature creep in structural alloys, and the performing of mechanical testing for high-temperature structural alloys. The article discusses hot tension testing and measurements of temperature and strain in the hot tension testing. It also provides an overview of hot compression testing.

This article presents examples of the visual fracture examination that illustrate the procedure as it applies to failure analysis and quality determination. It describes the techniques and procedures for the visual and light microscopic examination of fracture surfaces with illustrations. The article also describes microscopic and macroscopic features of the different fracture mechanisms with illustrations with emphasis on visual and light microscopy examination. The types of fractures considered include ductile fractures, tensile-test fractures, brittle fractures, fatigue fractures, and high-temperature fractures.

Stress-corrosion cracking (SCC) is a cracking phenomenon that occurs in susceptible alloys, and is caused by the conjoint action of tensile stress and the presence of a specific corrosive environment. This article provides an overview of the anodic dissolution mechanisms and cathodic mechanisms for SCC. It discusses the materials, environmental, and mechanical factors that control hydrogen embrittlement and SCC behavior of different engineering materials with emphasis on carbon and low-alloy steels, high-strength steels, stainless steels, nickel-base alloys, aluminum alloys, and titanium alloys.

This article describes the formability and surface contamination of the refractory metals such as niobium, tantalum, molybdenum, tungsten, and titanium-zirconium-molybdenum alloys. It reviews the factors that affect mechanical properties and formability during rolling and heat treatment. The effect of temperature on the formability of refractory metals is discussed. The article provides a description of the forming methods of sheet and preformed blanks using refractory metals. It also discusses the types of lubricants, including oils, soaps, waxes, silicones, graphite, and molybdenum disulphide, used in the forming of refractory metals.