Institute of Physics of Materials AS CR, v. v. i. > Projects > Origin and mechanism of anomalous slip in non-magnetic bcc metals

Origin and mechanism of anomalous slip in non-magnetic bcc metals

Investigatordoc. Ing. Roman Gröger, Ph.D.
Number of Project16-13797S
AgencyGrantová agentura České republiky
Duration2015-12-31 - 2018-12-30

Plastic deformation of bcc metals is governed by processes that are very different from those in
close-packed crystals. The biggest mystery is the occurrence of the anomalous slip whereby screw
dislocations move preferentially on low-stressed planes, which violates the Schmid law and thus makes
the yield criteria such as that due to Tresca inapplicable to bcc metals. While it is frequently seen in
tension for the VB-group metals it only exists under compression for the VIB-group metals. The objective
of this project is unravel the origin and mechanisms that lead to the anomalous slip in all VB-group (V, Nb
, Ta) and VIB-group (Mo, W) non-magnetic refractory bcc metals using a combination of direct
experiments on millimeter-sized single crystals and molecular statics simulations using the
state-of-the-art description of bonding. The slip traces predicted by our yield criteria will be compared
with those observed using optical microscopy on deformed samples. TEM measurements on selected
samples will determine the character of the dislocation networks on the planes of anomalous slip.


Gröger R., Chlup Z., Sojková T., Kuběna I.: Interplay of slip and twinning in niobium single crystals compressed at 77 K. J. Mater. Res. 34 (2019) 261-270

Gröger R., Vítek V.: Impact of non-Schmid stress components present in the yield criterion for bcc metals on the activity of {110}<111> slip systems. Comp. Mater. Sci. 159 (2019) 297-305


Gröger R., Chlup Z., Sojková T.: Deformation twinning in vanadium single crystals tested in compression at 77 K. Mater. Sci. Eng. A 737 (2018) 413-421

Gröger R., Chlup Z., Kuběna I., Kruml T.: Slip activity in molybdenum single crystals compressed at 77 K. Philos. Mag. 98 (2018) 2749-2768


Hernandez-Maldonado D., Gröger R., Ramasse Q., Hirsch P., Nellist P.: Evaluation of aberration-corrected optical sectioning for exploring the core structure of 1/2[111] screw dislocations in BCC metals. Microscopy and Microanalysis 23 (2017) 432-433

Gröger R., Vítek V., Lookman T.: Mesoscale plastic texture in body-centered cubic metals under uniaxial load. Phys. Rev. Mater. 1 (2017) 063601


Gröger R., Lookman T.: Mesoscopic description of dislocation patterning using the concept of incompatibility of strains. Solid State Phenom. 258 (2016) 87-92

Gröger R., Marchand B., Lookman T.: Dislocations via incompatibilities in phase-field models of microstructure evolution. Phys. Rev. B 94 (2016) 054105

Hernandez-Maldonado D., Yang H., Jones L., Gröger R., Hirsch P., Ramasse Q., Nellist P.: STEM optical sectioning for imaging screw dislocations core structures in BCC metals. Microscopy and Microanalysis 22 (2016) 1932-1933