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polycrystalline metals

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Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001335
EISBN: 978-1-62708-215-0
.... Discussion Many polycrystalline metals can become brittle and fail along grain boundaries when a low stress is applied. The brittleness has been attributed to intergranular weakness caused by the precipitation or segregation of impurities to grain boundaries. For example, Auger electron spectroscopy...
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001816
EISBN: 978-1-62708-241-9
... of the Ashby–Verrall model for a metallic polycrystalline arrangement for grain sizes of 1, 5, and 10 μm. The use of the σ/μ ratio, where μ is the shear modulus, allows the comparison of the experimental data with models for an arrangement of polycrystalline metallic materials and where μ (~70 GPa at 800...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003542
EISBN: 978-1-62708-180-1
... to be matched to the specimen for best results, and stereographic pairs are extremely helpful in revealing the surface topography. With most SEMs, the fracture surfaces of ceramic specimens need to have a thin coating with a conductive material, usually a metal, to get the best images. Thin metal coatings...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003532
EISBN: 978-1-62708-180-1
... of the light microscope has restricted its use for such work. Aside from the published light optical fractographs made by Zapffe (see Ref 5 for a review of many of these), very few optical fractographs of metallic materials have been published by others. Microfractography gained momentum with the development...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003554
EISBN: 978-1-62708-180-1
.... The fracture path is usually intergranular in polycrystalline metals having cubic crystal structures and is frequently transgranular in hexagonal close-packed metals. Changes in the alloy composition of either the structural or the embrittling metal have a strong influence on the embrittlement severity...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006765
EISBN: 978-1-62708-295-2
... also be performed using a 45 μm metal-bonded or a 30 μm resin-bonded diamond disc or with an RGD and 15 or 30 μm diamond, depending on the material. Rigid grinding discs contain no abrasive; they must be charged during use, and suspensions are the easiest way to do this. Polycrystalline diamond...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003545
EISBN: 978-1-62708-180-1
... behavior of a polycrystalline metal or alloy often is considered to begin at approximately one-third to one-half of its melting point (∼0.3 to 0.5 T M ) measured on an absolute temperature scale (degrees Kelvin or Rankine). However, this rule of thumb is not necessarily the criteria for engineering...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006780
EISBN: 978-1-62708-295-2
... to allow time-dependent rearrangement of structure. Creep behavior of a polycrystalline metal or alloy often is considered to begin at approximately one-third to one-half of its melting point (~0.3 to 0.5 T M ) measured on an absolute temperature scale (degrees Kelvin or Rankine). However, this rule...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006786
EISBN: 978-1-62708-295-2
... segregation. Thus, pure metals and single crystals are less susceptible to embrittlement but are not immune. The brittle fracture stress varies with the inverse square root of the average grain diameter (Hall-Petch equation). The fracture path is usually intergranular in polycrystalline metals having...
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
...) failures: In-service part failures caused by undesired surface layers: Surface metallurgy, roughness or topography damage associated with metal-removal practices can lead to workpiece rejection during inspection or in-service part failure. In-service part failures caused by metallurgical factors...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003543
EISBN: 978-1-62708-180-1
... be completely amorphous, oriented (as parallel alignment of carbon backbone chains in polymers), mixtures of crystalline and noncrystalline regions, or totally crystalline but in which crystalline regions are rotated with respect to each other (“polycrystalline”). In most metals, the metallic bonds between...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003538
EISBN: 978-1-62708-180-1
... geometric factors and materials aspects that influence the stress-strain behavior and fracture of ductile metals. It highlights fractures arising from manufacturing imperfections and stress raisers. The article presents a root cause failure analysis case history to illustrate some of the fractography...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006775
EISBN: 978-1-62708-295-2
... propagation fractography metals microscale models root-cause failure analysis specimen preparation void coalescence void nucleation THE CONCEPT OF DUCTILE AND BRITTLE BEHAVIOR generally applies to the macroscopic scale. However, there is no universally accepted transition point from ductile...
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.steel.c9001598
EISBN: 978-1-62708-232-7
... that intergranular voids did not pin the grain boundaries. Another drawback of a fine grained polycrystalline material operating at high temperatures is intercrystalline fracture. For metallic materials, creep becomes significant at homologous temperatures (T/T m ) greater than 0.4, where T is the operating...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006778
EISBN: 978-1-62708-295-2
... are rotated with respect to each other (polycrystalline). In most metals, metallic bonds between atoms typically result in a crystalline structure, which in most engineering metals are face-centered cubic (fcc), body-centered cubic (bcc), or hexagonal close-packed (hcp) structures. The formation...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006761
EISBN: 978-1-62708-295-2
... and forgings, weld heat-affected zones, and precious metals where small amounts of material are available. In addition, characterizing the mechanical behavior of anisotropic materials often requires compression testing. For isotropic polycrystalline materials, compressive behavior is correctly assumed...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003540
EISBN: 978-1-62708-180-1
... corrosion cracking steels INTERGRANULAR FRACTURE is the decohesion that may occur along a weakened grain boundary. Typically, the grain boundaries in polycrystalline materials are stronger than individual grains in a properly processed material below its creep-regime temperature. The grain boundaries...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006777
EISBN: 978-1-62708-295-2
... are thus the preferential region for congregation and segregation of impurities. Typically, the grain boundaries in polycrystalline materials are stronger than individual grains in a properly processed material below its creep-regime temperature. The grain boundaries are disruptions between the crystal...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003528
EISBN: 978-1-62708-180-1
... found in metals and their alloys as well as in polycrystalline ceramics (i.e., oxides, carbides, nitrides, etc.). The size of specimens that can be evaluated using XRD can vary widely from as small as the head of a pin to as large as a ship ( Ref 12 , 14 ), a building/structure ( Ref 15 , 16...
Series: ASM Handbook
Volume: 11
Publisher: ASM International
Published: 15 January 2021
DOI: 10.31399/asm.hb.v11.a0006768
EISBN: 978-1-62708-295-2
... in the weld metal on the unmasked side from shot peening a nickel alloy weldment. Source: Ref 40 Fig. 16 Typical constant-amplitude cyclic loading spectrum. Source: Ref 50 Fig. 17 Stress versus number of cycles to failure curves for as-hardened (gear A) and as-hardened plus double-shot...