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SUMMARY:Assessing the contribution of hydrogen-deformation interactions to
  hydrogen-induced intergranular fracture in nickel-base alloys - Dr Zachar
 y Harris. University of Virginia
DTSTART:20190409T130000Z
DTEND:20190409T140000Z
UID:TALK120553@talks.cam.ac.uk
CONTACT:Hilde Hambro
DESCRIPTION:Despite over a century of study\, hydrogen-induced premature f
 ailure of structural metals continues to negatively impact critical indust
 ries spanning the aerospace\, marine\, transportation\, and energy sectors
 . Efforts to mitigate this deleterious effect are undermined by an incompl
 ete understanding of the microscale processes governing hydrogen-induced d
 egradation. Recent literature posits that the governing mechanism for hydr
 ogen-induced intergranular failure is the decohesion of grain boundaries p
 rincipally driven by hydrogen-deformation interactions. However\, there is
  a lack of experiments which quantitatively establish the predominant cont
 ribution of hydrogen-deformation interactions to hydrogen-induced intergra
 nular cracking. Additionally\, the extension of such mechanisms into more 
 complex\, industrially-relevant alloys is hindered by the uncertain contri
 bution of alloy metallurgy to hydrogen-induced degradation.\n\nThe objecti
 ve of this presentation is to review two research activities at the Univer
 sity of Virginia which sought to understand the contribution of hydrogen-d
 eformation interactions to hydrogen embrittlement susceptibility in nickel
 -base alloys. The first half of the talk outlines recent experiments that 
 aimed to quantitatively evaluate the influence of mobile hydrogen-deformat
 ion interactions on hydrogen-induced intergranular cracking in polycrystal
 line nickel. The results of this effort quantitatively demonstrate that\, 
 while mobile H-deformation interactions do contribute to hydrogen-induced 
 intergranular fracture\, this contribution can be considered secondary in 
 nature. The second half of the talk describes our initial efforts to evalu
 ate the effect of hydrogen on the deformation behavior of a precipitation-
 hardened nickel-base alloy as a function of aging condition. Transmission 
 electron microscopy\, coupled with the analysis of work hardening behavior
 \, indicates that hydrogen induces a transition from particle shearing to 
 bypassing at smaller particle sizes. Moreover\, counter to previous findin
 gs in polycrystalline nickel\, evidence of increased propensity for cross-
 slip is also observed in the presence of hydrogen for these precipitation-
 hardened alloys. The talk then concludes with a brief overview of ongoing 
 experiments seeking to understand the effect of these bulk deformation res
 ults on the processes occurring within the fracture process zone.
LOCATION:Oatley Seminar Room\, Department of Engineering
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