Atomistic simulations of deformation behavior in nano- polycrystalline zirconium

C. J. RUESTES; G. BERTOLINO; M. RUDA; D. FARKAS

Florianópolos

Congreso; XI SBPMat - Brazilian MRS Meeting; 2012

MRS

In order to explore the mechanical properties of nano-polycrystalline hcp Zirconium, weperformed atomistic simulations using molecular dynamics (MD) [1] and potentials of theembedded atom (EAM) type [2]. We simulated stress-strain curves on samples of nano-polycrystalline hcp Zr and we studied the influence of grain size, strain rate, temperature andnumber of grains on these curves. The simulation blocks where created by a Voronoitessellation and consisted of columnar grains that were rotated randomly with respect to eachother about the [0001] axis so that the grain boundaries were all pure tilt with randommisorientation angles. Our results show that for grain sizes smaller than a critical size, theaverage flow stress of nano-polycrystalline hcp Zr decreases with the decreasing of the grainsize. This is known as the inverse Hall-Petch effect, which is a well known characteristic ofthe fcc metals [3]. Also the Young modulus increases with increasing grain size. These resultsare shown on Figure 1. Decreasing the strain rate by a factor of 5 lowered the average flowstress by a small amount. This effect was more important on the samples with larger grainsizes. As expected, increasing the temperature from 10K to 300K lowered significantly theflow stress. We also analyzed the effect of the number of grains in the samples and found thatthe number of grains used in our simulations were in average representative of thepolycrystalline properties. Deformation mechanisms were correlated to grain sizes.