Quantifying residual stress in Helium-implanted surfaces and its implication for blistering

Abstract

Helium implantation in surfaces is of interest for plasma facing materials and other nuclear applications. Vanadium as both a representative bcc material and a material relevant for fusion applications is implanted using a Helium ion beam microscope, and the resulting swelling and nanomechanical properties are quantified. These values are put in correlation to data obtained from micro residual stress measurements using a focused ion beam based ring-core technique. We found that the swelling measured is similar to literature values. Further we are able to measure the surface stress caused by the implantation and find it approaches the yield strength of the material at blistering doses.The simple calculations performed in the present work, along with several geometrical considerations deduced from experimental results confirm the driving force for blister formation comes from bulging resulting mainly from gas pressure buildup, rather than solely stress induced buckling.

Current trends in nanomechanical testing research

“…As evidenced by the high number of related contributions, the use of the FIB has become essential in the field of nanomechanical testing [17,18,[20][21][22]. This has inevitably raised concerns about possible measurement artifacts due to ion damage incurred during the specimen preparation [20,[23][24][25]. While detrimental effects can be ruled out for some applications [20], in other cases, workarounds are actively being developed to minimize [24] or to completely avoid [23] exposure of the samples to highly energetic ion beams.…”

“…This focus issue also witnesses the use of other emerging techniques, such as atom probe tomography (APT), which provides chemical composition mapping with strongly enhanced spatial resolution [29,33]. Regardless of the nanomechanical testing method, post-mortem analyses appear to greatly benefit from the increasing availability of image processing algorithms, such as digital image correlation [11,25,35,36].…”