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microsegregation
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Published: 01 December 1993
Fig. 20 Detailed view of microsegregation observed on tooth F-23. Nital etch. 14.8×
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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001167
EISBN: 978-1-62708-228-0
... pearlite aligned in bands along the longitudinal direction of the pipe. The pearlite grains occur in lean alloy microsegregation bands where local hardenability is low. The structure, shown in Fig. 5 , is typical of a low alloy hardenable steel in the normalised condition, Fig. 5 Upper bainitic...
Abstract
Visual examination, optical and scanning electron microscopy were used to determine the cause of failure in the connector groove of a marine riser coupling. The specified steel was AISI 4142 (0.40 to 0.45% C; 0.75 to 1.00% Mn; 0.20 to 0.35% Si; 0.80 to 1.10% Cr; 0.15 to 0.25% Mo) normalized from 9000C. Microscopic examination revealed the crack's initiation point and subsequent propagation. SEM examination of chemically stripped corrosion showed that corrosion fatigue and stress corrosion might have contributed to the initial slow crack growth. Impact tests revealed a fracture transition temperature in excess of 1000C. The sequence of events leading to failure was detailed. The main recommendation was to quench and temper existing couplings and to use a lower carbon quenched and tempered steel for new couplings.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003510
EISBN: 978-1-62708-180-1
..., and 1144. As a rule, steels with carbon contents and hardenability greater than 1037 are difficult to water quench ( Ref 22 ). Some steel grades with high manganese are prone to microsegregation of manganese, gross segregation of chromium, and thus are prone to cracking. These include 1340, 1345, 1536...
Abstract
This article provides an overview of the effects of various material- and process-related parameters on residual stress, distortion control, cracking, and microstructure/property relationships as they relate to various types of failure. It discusses phase transformations that occur during heat treating and describes the metallurgical sources of stress and distortion during heating and cooling. The article summarizes the effect of materials and the quench-process design on distortion and cracking and details the effect of cooling characteristics on residual stress and distortion. It also provides information on the methods of minimizing distortion and tempering. The article concludes with a discussion on the effect of heat treatment processes on microstructure/property-related failures.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001301
EISBN: 978-1-62708-215-0
... in the immediate vicinity of the suspected fracture origin on tooth F-23. In the etched condition, the structure at this location showed evidence that segregation occurred during solidification ( Fig. 20 ). Fig. 20 Detailed view of microsegregation observed on tooth F-23. Nital etch. 14.8...
Abstract
Gears in a strip mining dragline failed in service. The material was identified as a low-alloy (NiCrMoV) steel. SEM analysis indicated that the initial fracture and subsequent fractures resulted from impact or a suddenly applied load. Mechanical testing indicated that the gears had low impact strength. Failure was attributed to low toughness caused by the absence of, or improper, heat treatment. Casting defects identified during metallographic examination were determined to be the fracture initiation site, but were considered less significant than the low as-received impact strength of the material. It was recommended that the equipment manufacturer implement an appropriate heat treatment to meet the impact requirements of the application.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001111
EISBN: 978-1-62708-214-3
.... Additionally, by means of electron microprobe analysis, it was found that microsegregation of titanium, sulphur and manganese occurred in the dendrite interstices of the crack surface. The microsegregation of titanium and manganese in combination with sulfur can be expected to broaden the temperature range...
Abstract
A catastrophic brittle fracture occurred in a welded steel (ASTM A517 grade H) trapezoidal cross-section box girder while the concrete deck of a large bridge was being poured. The failure occurred across the full width of a 57 mm (2 1 4 in.) thick, 760 mm (30 in.) wide flange and arrested 100 mm (4 in.) down the slant web. Failure analysis revealed a major deficiency in fracture toughness. The failure occurred as a brittle fracture after the formation of a welding hot crack and approximately 40 mm (1 1 2 in.) of slow crack growth. It was recommended that bridges fabricated from this grade of steel undergo frequent inspection and that stringent test requirements be imposed as a condition of use in non-redundant main load-carrying components.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006826
EISBN: 978-1-62708-329-4
..., or calcium can be added to hypoeutectic aluminum-silicon alloys to progressively change the silicon lamellae into rounded particles, and phosphorus refines the size of silicon particles in hypereutectic aluminum-silicon alloys ( Ref 26 ). Microsegregation in wrought alloys is a microstructural defect...
Abstract
The first part of this article focuses on two major forms of machining-related failures, namely machining workpiece (in-process) failures and machined part (in-service) failures. Discussion centers on machining conditions and metallurgical factors contributing to (in-process) workpiece failures, and undesired surface layers and metallurgical factors contributing to (in-service) machined part failures. The second part of the article discusses the effects of microstructure on machining failures and their preventive measures.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001775
EISBN: 978-1-62708-241-9
... and stereoscopic examination of the internal (gas-side) and external surfaces of the tube, chemical and metallographic analysis of the alloy, determination of crack propagation mode (intergranular or transgranular), and estimation of the local chemical composition and microsegregation at grain boundaries. Chemical...
Abstract
A bent Ni-Cu Monel 400 alloy tube, which operated as part of a pipeline in a petrochemical distillery, failed by through-thickness cracking. The pipeline was used to carry a stream of gaseous hydrocarbons containing hydrochloric acid (HCl) into a reaction tower. The tower provided a caustic solution (NaOH) to remove HCl from the stream, before the latter was directed to a burner. Metallographic examination showed that the cracks were intergranular and were frequently branched. Although nominal chemical composition of the component was found within the specified range, energy dispersive x-ray analysis (EDXA) indicated significant segregation of sulfur and chlorine along the grain boundaries. Failure was attributed to hypochlorous-acid (HClO)-induced stress-corrosion cracking (SCC). The HClO was formed by the reaction of HCl with atmospheric O 2 that entered the tube during shutdowns and startups. Residual stresses, originating from in situ bend forming of the tube during assembly of the line, provided a driving force for crack growth, and the segregation of sulfur on grain boundaries made the material more susceptible to cracking.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006835
EISBN: 978-1-62708-329-4
.... Consequently, the dendrite arms are stronger and, on working, do not deform and flow as readily as the matrix in which they are incorporated. Microsegregation characterizes concentrations of elements in interdendritic regions that range in size from a few to several hundred micrometers. By contrast...
Abstract
The primary purpose of this article is to describe general root causes of failure that are associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be common sources of failure-inducing defects in the bulk working of wrought products. The article addresses the types of flaws or defects that can be introduced during the steel forging process itself, including defects originating in the ingot-casting process. Defects found in nonferrous forgings—titanium, aluminum, and copper and copper alloys—also are covered.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006831
EISBN: 978-1-62708-329-4
... segregate during solidification. The variable distribution of chemical composition on the microscopic level in a microstructure, such as dendrites and grains, is referred to as microsegregation. Variation on the macroscopic level is called macrosegregation. Microsegregation characterizes concentrations...
Abstract
The information provided in this article is intended for those individuals who want to determine why a casting component failed to perform its intended purpose. It is also intended to provide insights for potential casting applications so that the likelihood of failure to perform the intended function is decreased. The article addresses factors that may cause failures in castings for each metal type, starting with gray iron and progressing to ductile iron, steel, aluminum, and copper-base alloys. It describes the general root causes of failure attributed to the casting material, production method, and/or design. The article also addresses conditions related to the casting process but not specific to any metal group, including misruns, pour shorts, broken cores, and foundry expertise. The discussion in each casting metal group includes factors concerning defects that can occur specific to the metal group and progress from melting to solidification, casting processing, and finally how the removal of the mold material can affect performance.
Book Chapter
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003508
EISBN: 978-1-62708-180-1
Abstract
This article focuses on the general root causes of failure attributed to the casting process, casting material, and design with examples. The casting processes discussed include gravity die casting, pressure die casting, semisolid casting, squeeze casting, and centrifugal casting. Cast iron, gray cast iron, malleable irons, ductile iron, low-alloy steel castings, austenitic steels, corrosion-resistant castings, and cast aluminum alloys are the materials discussed. The article describes the general types of discontinuities or imperfections for traditional casting with sand molds. It presents the international classification of common casting defects in a tabular form.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.9781627083294
EISBN: 978-1-62708-329-4
Book Chapter
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003507
EISBN: 978-1-62708-180-1
..., such as sulfur and phosphorus in steel, than the interdendritic regions. Consequently, the dendrite arms are stronger and, on working, do not deform and flow as readily as the matrix in which they are incorporated. Microsegregation characterizes concentrations of elements in interdendritic regions that range...
Abstract
This article describes the general root causes of failure associated with wrought metals and metalworking. This includes a brief review of the discontinuities or imperfections that may be the common sources of failure-inducing defects in bulk working of wrought products. The article discusses the types of imperfections that can be traced to the original ingot product. These include chemical segregation; ingot pipe, porosity, and centerline shrinkage; high hydrogen content; nonmetallic inclusions; unmelted electrodes and shelf; and cracks, laminations, seams, pits, blisters, and scabs. The article provides a discussion on the imperfections found in steel forgings. The problems encountered in sheet metal forming are also discussed. The article concludes with information on the causes of failure in cold formed parts.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003518
EISBN: 978-1-62708-180-1
... material manufacturing Excessive microsegregation causes inability to achieve post heat treat mechanical properties. Material supplier is blamed. Additional investigation is performed on how to improve heat treat line, to make process more robust. Design phase Designer does not know accuracy...
Abstract
Failure analysis is a process that is performed to determine the causes or factors that have led to an undesired loss of functionality. This article describes some of the factors and conditions that might be considered when approaching a failure analysis problem. It focuses on the key principles, objectives, practices, and procedures of failure analysis. The article provides guidelines on the preparation of a protocol for a failure analysis. It also demonstrates the proper approaches to failure analysis.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006754
EISBN: 978-1-62708-295-2
... Physical causes and time of occurrence Physical causes Example Likely effects of findings Alternative effect(s) of findings Raw material manufacturing Excessive microsegregation causes inability to achieve post-heat-treatment mechanical properties. Material supplier is blamed...
Abstract
Failure analysis is a process that is performed in order to determine the causes or factors that have led to an undesired loss of functionality. This article is intended to demonstrate proper approaches to failure analysis work. The goal of the proper approach is to allow the most useful and relevant information to be obtained. The discussion covers the principles and approaches in failure analysis work, objectives and scopes of failure analysis, the planning stages for failure analysis, the preparation of a protocol for a failure analysis, practices used by failure analysts, and procedures of failure analysis.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006838
EISBN: 978-1-62708-329-4
... Swelling from the melt pool Chemical composition change due to vaporization of elements Alloy microsegregation Surface defects in metal additive manufacturing parts Table 3 Surface defects in metal additive manufacturing parts Weld tracks Protruding unmelted or partially melted...
Abstract
This article provides an overview of metal additive manufacturing (AM) processes and describes sources of failures in metal AM parts. It focuses on metal AM product failures and potential solutions related to design considerations, metallurgical characteristics, production considerations, and quality assurance. The emphasis is on the design and metallurgical aspects for the two main types of metal AM processes: powder-bed fusion (PBF) and directed-energy deposition (DED). The article also describes the processes involved in binder jet sintering, provides information on the design and fabrication sources of failure, addresses the key factors in production and quality control, and explains failure analysis of AM parts.
Book Chapter
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003548
EISBN: 978-1-62708-180-1
Abstract
This article addresses the forms of corrosion that contribute directly to the failure of metal parts or that render them susceptible to failure by some other mechanism. It describes the mechanisms of corrosive attack for specific forms of corrosion such as galvanic corrosion, uniform corrosion, pitting and crevice corrosion, intergranular corrosion, and velocity-affected corrosion. The article contains a table that lists combinations of alloys and environments subjected to selective leaching and the elements removed by leaching.
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006783
EISBN: 978-1-62708-295-2
Abstract
Corrosion is the electrochemical reaction of a material and its environment. This article addresses those forms of corrosion that contribute directly to the failure of metal parts or that render them susceptible to failure by some other mechanism. Various forms of corrosion covered are galvanic corrosion, uniform corrosion, pitting, crevice corrosion, intergranular corrosion, selective leaching, and velocity-affected corrosion. In particular, mechanisms of corrosive attack for specific forms of corrosion, as well as evaluation and factors contributing to these forms, are described. These reviews of corrosion forms and mechanisms are intended to assist the reader in developing an understanding of the underlying principles of corrosion; acquiring such an understanding is the first step in recognizing and analyzing corrosion-related failures and in formulating preventive measures.
Series: ASM Handbook
Volume: 11A
Publisher: ASM International
Published: 30 August 2021
DOI: 10.31399/asm.hb.v11A.a0006808
EISBN: 978-1-62708-329-4
Abstract
This article describes some of the welding discontinuities and flaws characterized by nondestructive examinations. It focuses on nondestructive inspection methods used in the welding industry. The sources of weld discontinuities and defects as they relate to service failures or rejection in new construction inspection are also discussed. The article discusses the types of base metal cracks and metallurgical weld cracking. The article discusses the processes involved in the analysis of in-service weld failures. It briefly reviews the general types of process-related discontinuities of arc welds. Mechanical and environmental failure origins related to other types of welding processes are also described. The article explains the cause and effects of process-related discontinuities including weld porosity, inclusions, incomplete fusion, and incomplete penetration. Different fitness-for-service assessment methodologies for calculating allowable or critical flaw sizes are also discussed.