This article considers four types of high-strength structural steels: heat-treated low-alloy steels, as-rolled carbon-manganese steels, heat-treated (normalized or quenched and tempered) carbon steels, and as-rolled high-strength low-alloy (HSLA) steels (which are also known as microalloyed steels). The article places emphasis on HSLA steels, which are an attractive alternative in structural applications because of their competitive price per-yield strength ratios. HSLA steels are primarily hot-rolled into the usual wrought product forms and are furnished in the as-hot-rolled condition. In addition to hot-rolled products, HSLA steels are also furnished as cold-rolled sheet and forgings. This article describes the different categories of HSLA steels and provides a summary of characteristics and intended uses of HSLA steels described in the American Society for Testing and Materials (ASTM) specifications. The article also presents some applications of HSLA steels.

This article describes the types of steels, including high-strength structural carbon steels and high-strength low-alloy steels (HSLA), available in all standard wrought forms such as sheet, strip, plate, structural shapes, bars, bar-size shapes. It discusses the special sections that are characterized by higher yield strengths than those of plain carbon structural steels. The article tabulates the typical chemical compositions, tensile properties, heat treatment, product sizes, plate thickness and intended uses of high-strength steels. Further, it presents a short note on heat treated structural low-alloy grades.

Two high-strength low-alloy (HSLA) families, acicular-ferrite steels and pearlite-reduced steels, contain microalloying additions of vanadium and niobium. Vanadium, niobium, and titanium combine preferentially with carbon and/or nitrogen to form a fine dispersion of precipitated particles in the steel matrix. This article summarizes the metallurgical effects of vanadium, niobium, molybdenum, and titanium. The metallurgical fundamentals were first applied to forgings in the early 1970s. The ultimate strength of first- and second-generation microalloy steels is adequate for many engineering applications, but these steels do not achieve the toughness of conventional quenched and tempered alloys under normal hot-forging conditions. Third-generation microalloy steels differ from their predecessors in that they are direct quenched from the forging temperature to produce microstructures of lath martensite with uniformly distributed temper carbides. Without subsequent heat treatment, these materials achieve properties, including toughness, similar to those of standard quenched and tempered steels.

Structural steels with very high strength levels are often referred to as ultrahigh-strength steels. This article describes the commercial structural steels capable of a minimum yield strength of 1380 MPa (200 ksi). The ultrahigh-strength class of constructional steels includes several distinctly different families of steels. The article focuses on medium-carbon low-alloy steels, medium-alloy air-hardening steels, and high fracture toughness steels. The medium-carbon low-alloy family of ultrahigh-strength steels includes AISI/SAE 4130, the higher-strength 4140, and the deeper hardening, higher-strength 4340. Also from this family are descriptions for the 300M, D-6a and D-6ac, 6150, and 8640 steels. The medium-alloy air-hardening family of ultrahigh-strength steels includes H11 modified and H13 steels. The high fracture toughness family of ultrahigh-strength steels includes HP-9-4-30 steel and AF1410 steel. The article explains the mechanical properties and the heat treatments of the medium-carbon low-alloy steels, medium-alloy air-hardening steels, and high fracture toughness steels.

This article discusses the applications of high-strength aluminum powder metallurgy (P/M) alloys, detailing the advantages, properties, and the various steps involved in P/M technology, including powder production, powder processing, and degassing and consolidation. Three areas of design efforts to push the inherent advantages of aluminum alloys to new limits are also covered: high ambient-temperature strength with improved corrosion and stress corrosion cracking resistance; improved elevated-temperature properties so aluminum alloys can more effectively compete with titanium alloys; and increased stiffness and/or reduced density for aluminum alloys to compete with organic composites. An appendix provides a detailed account of the properties, processing, and applications of conventionally pressed and sintered aluminum P/M alloys.

This article provides information on the classification of high-strength steels (HSS) and advanced high-strength steels (AHSS) and tabulates designation of HSS and AHSS as recommended by the American Iron and Steel Institute. It reviews the major grades of HSS and AHSS that are used or will potentially be used in industrial applications. The article discusses different stamping issues such as edge cracking and springback, encountered during forming of AHSS, and lists guidelines for reducing springback in stamped components. It concludes with a discussion on the major advantages and disadvantages of using HSS and AHSS in automotive applications.

This article discusses the conditions for collapse in center-cracked panels and describes the energy criterion for fracture. Measurement of toughness of any material by means of tensile and crack test is discussed. The procedures to be followed for linear elastic fracture mechanics cases are reviewed, along with elastic-plastic fracture mechanics and plastic fracture mechanics procedures with the aid of residual strength diagram. The article also explains the geometry factors needed to determine the toughness of materials.

This article briefly reviews the factors that affect the fatigue strength of aluminum alloy weldments. It discusses a number of factors influencing the fatigue performance of welded aluminum joints. The article describes the effects of fatigue behavior on weldments based on parent alloy selection, weld joint configuration, and residual stress. The two categories of techniques that can result in improved fatigue life, such as modification of weld toe geometry and introduction of compressive residual stresses in the surface material, are detailed. The article analyzes the influence of section size on fatigue performance of aluminum alloy weldments.

This article provides information on the typical experimental observations of formation and propagation of small fatigue cracks under various stress states and explores the relation to long crack fracture mixed-mode fracture mechanics. It discusses state I crystallographic and stage II normal stress-dominated growth, along with some observations regarding the influence of combined stress state on the propagation of small cracks. The article discusses the differences between low-cycle fatigue and high-cycle fatigue (HCF) behaviors. Several other features of multiaxial fatigue are also explained, including mean stress effects, sequences of stress/strain amplitude or stress state, nonproportional loading and cycle counting, and HCF fatigue limits. In addition, the article covers the formation and propagation of cracks on the order of several grain sizes in diameter in initially isotropic and ductile structural alloys.

This article presents the damage tolerance criteria for military composite aircraft structures to safely operate the structures with initial defects or in-service damage. It describes the effects of defects, such as wrinkles in aircraft structures, and the reduction in compressive strength and tensile strength. The article reviews low velocity impacts in aircraft structures in terms of resin toughness, laminate thickness, specimen size and impactor mass, and post-impact fatigue. It explains the tension strength analysis, such as linear elastic fracture mechanics and R-curve methods, to predict the residual strength of the structures.

Air hardening steel is a type of steel that has deep hardenability and can be hardened in large sections by air cooling. This article discusses the principles of heat treatment of air-hardening steel, and describes the recommended heat treating practices for air-hardening high-strength structural steels, namely, H11 Mod, H13 steel, 300M steel, D-6A and D-6AC, and AF1410 steel. It also provides information on recommended heat treating practices for air-hardening martensitic stainless steels.

Ultrahigh-strength steels are designed to be used in structural applications where very high loads are applied and often high strength-to-weight ratios are required. This article discusses the composition, mechanical properties, processing, product forms, and applications of commercial structural steels capable of a minimum yield strength of 1380 MPa (200 ksi). These include medium-carbon low-alloy steels, such as 4340, 300M, D-6a and D-6ac steels; medium-alloy air-hardening steels, such as HI1 modified steel and H13 steel; high fracture toughness steels, such as HP-9-4-30, AF1410, and AerMet 100 steels; and maraging steels.

This article presents a comprehendable and comprehensive physics-based approach for characterizing the strength of fiber-reinforced polymer composites. It begins with background information on the goals and attributes of this method. The article then addresses the characterization of fiber failures in laminates, because these are at the highest strengths that can be attained and, therefore, are usually the design objective. An exception would be if the design goal is to maximize energy absorption, rather than static strength. The discussion proceeds to situations in which the matrix fails first, either by intent, by design error, or because of impact damage. The state of the modeling propagation and arrest of matrix damage follows. Comparisons of this physics-based approach are then made to empirically based failure theories.

This datasheet provides information on composition limits, mill product specifications, fabrication characteristics, processing effects on physical and mechanical properties, and applications of high-strength Al-Mg-Mn-Cr alloy 5456.

This datasheet provides information on key alloy metallurgy, fabrication characteristics, processing effects on physical and mechanical properties, and applications of Al-Mg high-strength casting alloy 535.0.

This datasheet provides information on key alloy metallurgy, mill product specifications, processing effects on physical and mechanical properties, and applications of high-strength aerospace alloys 2024 and Alclad 2024. It contains tables that list values of tensile property limits for 2024 sheet, plate, and round product forms. Figures illustrate the effect of stretching and aging on toughness of the 2024 sheet and the effect of temperature on tensile properties of 1.0 mm thick Alclad 2024-T3 sheet.

The high-strength plate alloy 2324 is a modification of 2024 alloy composition and process conditions to increase strength in both plate and extrusions without a loss in fracture toughness and other characteristics. This datasheet provides information on key alloy metallurgy, as well as the effects of processing on mechanical properties of this 2xxx series alloy. A comparison of fracture toughness of 2324-T39 to 2024-T351 is presented.

Alloys 242.0 and A242.0 are age-hardenable casting alloys with excellent strength at elevated temperatures. This datasheet provides information on key alloy metallurgy, processing effects on physical and mechanical properties, fabrication characteristics, and application characteristics of these 2xxx series alloys.

This datasheet provides information on key alloy metallurgy, processing effects on physical and mechanical properties, fabrication characteristics, and applications of high-strength structural alloy 7050.