Effect of Misorientation on the Compression of Highly Anisotropic Single‐Crystal Micropillars

Abstract

The effect of crystal misorientation, geometrical tilt, and contact misalignment on the compression of highly anisotropic single crystal micropillars was assessed by means of crystal plasticity finite element simulations. The investigation was focused in single crystals with the NaCl structure, like MgO or LiF, which present a marked plastic anisotropy as a result of the large difference in the critical resolved shear stress between the “soft” {110}〈110〉 and the “hard” {100}〈110〉 active slip systems. It was found that contact misalignment led to a large reduction in the initial stiffness of the micropillar in crystals oriented in the soft and hard direction. The crystallographic tilt did not modify, however, the initial crystal stiffness. From the viewpoint of the plastic response, none of the effects analyzed led to significant differences in the flow stress when the single crystals were oriented along the “soft” [100] direction. Large differences were found, however, if the single crystal was oriented in the “hard” [111] direction as a result of the activation of the soft slip system. Numerical simulations were in very good agreement with experimental literature data.

High temperature micropillar compression of Al/SiC nanolaminates

“…The initial loading slope of the stress-strain curves at 23 °C and 100 °C was much more compliant than that expected from purely elastic loading. This behavior was attributed to the local plastic yielding at the top of the micropillar, because of slight misalignments between the micropillar surface and the flat punch, before full contact is established between the two [37]. This effect is clearly seen in the variation in elastic modulus of the micropillar, determined from the slope of the unloading steps during the test, as a function of the applied displacement (Fig.…”

Multiscale modeling of the mechanical behavior of IN718 superalloy based on micropillar compression and computational homogenization

“…The total number of elements in the model was 15359 elements, following a mesh convergence analysis. The flat punch was modeled as a rigid body, with a lateral stiffness of 10 lN/nm, which approximately corresponds to the lateral stiffness of the indenter used in the experiment [37]. The contact between the flat punch and the micropillar head was modeled according to a Coulomb friction Table 1 Elastic constants of the cubic IN718 single crystal [21].…”

“…The contact between the flat punch and the micropillar head was modeled according to a Coulomb friction Table 1 Elastic constants of the cubic IN718 single crystal [21]. model, with a friction coefficient of 0.1 [37]. The base of the supporting material was fully constrained, while a flat punch was moved in the vertical direction at a constant speed.…”

Review Article: Case studies in future trends of computational and experimental nanomechanics

“…Soler and Aldareguia show that misalignments induce significant changes in the flow stress of LiF micropillars. 165 In the case of NPs, Issa et al investigate the mechanical properties of MgO perfectly shaped h001i-nanocubes and emphasize the benefits of such geometry compared to the use of nanospheres (e.g., on the slip system analysis). 120 Setup alignment and sample orientation characterization are crucial to correctly measure mechanical properties and rigorously identify elementary processes of deformation.…”