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CATEGORIES:Engineering - Mechanics and Materials Seminar Seri
 es
SUMMARY:Assessing the contribution of hydrogen-deformation
  interactions to hydrogen-induced intergranular fr
 acture in nickel-base alloys - Dr Zachary Harris. 
 University of Virginia
DTSTART;TZID=Europe/London:20190409T140000
DTEND;TZID=Europe/London:20190409T150000
UID:TALK120553AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/120553
DESCRIPTION:Despite over a century of study\, hydrogen-induced
  premature failure of structural metals continues 
 to negatively impact critical industries spanning 
 the aerospace\, marine\, transportation\, and ener
 gy sectors. Efforts to mitigate this deleterious e
 ffect are undermined by an incomplete understandin
 g of the microscale processes governing hydrogen-i
 nduced degradation. Recent literature posits that 
 the governing mechanism for hydrogen-induced inter
 granular failure is the decohesion of grain bounda
 ries principally driven by hydrogen-deformation in
 teractions. However\, there is a lack of experimen
 ts which quantitatively establish the predominant 
 contribution of hydrogen-deformation interactions 
 to hydrogen-induced intergranular cracking. Additi
 onally\, the extension of such mechanisms into mor
 e complex\, industrially-relevant alloys is hinder
 ed by the uncertain contribution of alloy metallur
 gy to hydrogen-induced degradation.\n\nThe objecti
 ve of this presentation is to review two research 
 activities at the University of Virginia which sou
 ght to understand the contribution of hydrogen-def
 ormation interactions to hydrogen embrittlement su
 sceptibility in nickel-base alloys. The first half
  of the talk outlines recent experiments that aime
 d to quantitatively evaluate the influence of mobi
 le hydrogen-deformation interactions on hydrogen-i
 nduced intergranular cracking in polycrystalline n
 ickel. The results of this effort quantitatively d
 emonstrate that\, while mobile H-deformation inter
 actions do contribute to hydrogen-induced intergra
 nular fracture\, this contribution can be consider
 ed secondary in nature. The second half of the tal
 k describes our initial efforts to evaluate the ef
 fect of hydrogen on the deformation behavior of a 
 precipitation-hardened nickel-base alloy as a func
 tion of aging condition. Transmission electron mic
 roscopy\, coupled with the analysis of work harden
 ing behavior\, indicates that hydrogen induces a t
 ransition from particle shearing to bypassing at s
 maller particle sizes. Moreover\, counter to previ
 ous findings in polycrystalline nickel\, evidence 
 of increased propensity for cross-slip is also obs
 erved in the presence of hydrogen for these precip
 itation-hardened alloys. The talk then concludes w
 ith a brief overview of ongoing experiments seekin
 g to understand the effect of these bulk deformati
 on results on the processes occurring within the f
 racture process zone.
LOCATION:Oatley Seminar Room\, Department of Engineering
CONTACT:Hilde Hambro
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