Effect of grain size distribution on plastic strain recovery

Plastic deformation is size dependent, this is observed in experiments and simulations and has a fundamental effect in crystalline materials with average grain size in the nanometer range. Recent experiments show that plastic deformation is not only affected by the average grain size but also by the grain size distribution. One of the most notorious aspects is that nanocrystalline metals recover plastic strain after unloading. Here, we perform numerical simulations that show that plastic strain recovery is driven by the inhomogeneous stress distribution observed in samples with large variations in grain size. Our model predicts that the fraction of plastic strain recovery increases with the macroscopic strain applied to the sample and that the recovery rate increases as the volume fraction of larger grains decreases.