Grain Boundary Microstructure-Controlled Superplasticity in Al-Li-Cu-Mg-Zr Alloy

Abstract

Grain boundary microstructure-controlled superplasticity in an Al-Li alloy is discussed on the basis of OIM observations using the specimens with different grain boundary microstructures. The specimens having the homogeneous {110} textured grains with a high frequency of low-angle boundaries showed superplasticity, whereas the specimen having a heterogeneous and randomly oriented grains with a high frequency of random boundaries did not yield superplasticity. Cavities were preferentially formed at the triple junctions where two or three random boundaries interconnected. From those results, the optimum grain boundary microstructure for superplasticity is discussed in connection with the relationship between grain boundary character distribution (GBCD) and triple junction character distribution. The strain rate change tests were carried out during deformation in order to rejuvenate initially introduced optimal grain boundary microstructure. The superplasticity can be improved by the strain rate change test resulting in an increase of the frequency of low angle boundaries at the early work softening stage of deformation.

Characterization of Special Grain Boundaries and Triple Junctions in CuxNi1‐x Alloys upon Deformation and Annealing

“…Hence, for decades the microstructure of a material has been evaluated and analyzed in terms of its GB types and network . In this context, GBs − specifically the energy of GBs − has been explored as a way to make a material more thermally stable and resistant to crack nucleation: As random high‐angle GBs (HAGBs) and their conjunctions are often prone to crack nucleation, one approach is to enhance the fraction of coincidence site lattice (CSL)‐GBs, with low , which relates to their relatively low excess energy . Of special interest are 3‐GBs, with a specific interest in the triple junction (TJ) that these GBs are part of .…”

Grain Boundary Character Distributions in Nanocrystalline Metals Produced by Different Processing Routes

“…[39,48,49] Based on UFG studies, this will promote ductility because RHAGB's are more susceptible to grain boundary sliding. [21,61] Molecular dynamics simulations indicate that this enhancement might be even greater in nanocrystalline materials, given the increased grain boundary area. [62] However, the high RHAGB fraction is also likely to leave the microstructure more vulnerable to coarsening because RHAGBs are more prone to thermal migration than are low energy boundaries.…”

Assessment of mixed mode loading on macroscopic fatigue crack paths in thick section Al–Cu–Li alloy plate

“…The present work does not include nanoscale characterisation (e.g. through transmission electron microscopy) of grain boundaries, and for general assessments of grain boundaries in related 3 rd generation Cu and Zr containing Al-Li alloys the reader is referred to [37,48,49,50].…”