ASM Online Member Community

  • 1.  Thoughts on Fracture of Metals

    Posted 04-27-2022 09:15
    During the pandemic in 2020 a book from John Campbell (Noted casting technology guru) titled "The Mechanisms of Metallurgical Failure - The Origin of Fracture" Butterworth-Heinemann/Elsevier  was published and cites a profound Thesis that "entrainment defects" have been overlooked thoughout the history of metallurgy degrading all metals so that they fracture - when as predicted by the electron theory metals/alloys shoudl NEVER fracture - implying redcution in area in a tensile test is a direct measure of the quality of any metal.   

    The question is if all "entrainment defects" were eliminated that metal and alloys will deform down to nearly a single atom!  So one should be able in theory,  grip a small section on a chunk of metal (whisker) and pull (drawn) all the metal in the chunk to that size in a long length conserving only mass.

    ------------------------------
    Edward Vojcak
    Senior Metallurgical Engineer
    SGS North America
    Blue Island IL
    (708) 595-8734
    ------------------------------
    Data Ecosystem - Global Materials Platform


  • 2.  RE: Thoughts on Fracture of Metals

    Posted 04-28-2022 02:01
    Just a question, Edward.
    Do not we have the same when pulling a pure Copper wire we are able to activate many subsequent slip system and we break the wire when it is reduced to just a puntiform tip?

    ------------------------------
    Donato FIRRAO FASM
    Professor
    Politecnico di Torino
    TORINO
    +393351494032
    Italy
    ------------------------------

    Data Ecosystem - Global Materials Platform


  • 3.  RE: Thoughts on Fracture of Metals

    Posted 04-28-2022 07:22
      |   view attached
    Yes Donato I agree, in fact the question for aluminum (Campbell's gadfly) in Chin/Hosford/Backofen back in 1964-  tensile tests on zone purified aluminum draws to a point if zone purified  - see attached.   I don't think zone purificaition can remove oxides? also are all coppers completely free of oxygen?even the socalled OF coppers?

    Also, P. Bridgeman's work on many metals/alloys tensile tested under hydrostatic pressure - usually drawn to a point - dislocation generated voids around oxides and NMI kept closed - but are these entraped contaminated still active in preventing a metal reaching it projected deformation behavoir that Campbell assests the metal/ally shoudl in the "pure" state?

    I think Prof. Campbell raises a few questions that have never been resolved satisfactorly -but simply avoided and addressing simpler issues/questions such as grain size, NMI engineering, composites,  indignious precipitates, etc.

    ------------------------------
    Edward Vojcak
    Senior Metallurgical Engineer
    SGS North America
    Blue Island IL
    (708) 595-8734
    ------------------------------

    Attachment(s)

    Data Ecosystem - Global Materials Platform