Article

Metallurgical and Materials Transactions A

, Volume 40, Issue 8, pp 1835-1850

Open Access This content is freely available online to anyone, anywhere at any time.

Mechanical Behavior and Microstructural Development of Low-Carbon Steel and Microcomposite Steel Reinforcement Bars Deformed under Quasi-Static and Dynamic Shear Loading

  • L.M. DoughertyAffiliated withMST-8, Los Alamos National LaboratoryWCM-1, Los Alamos National Laboratory Email author 
  • , E.K. CerretaAffiliated withMST-8, Los Alamos National Laboratory
  • , G.T. GrayIIIAffiliated withMST-8, Los Alamos National Laboratory
  • , C.P. TrujilloAffiliated withMST-8, Los Alamos National Laboratory
  • , M.F. LopezAffiliated withMST-8, Los Alamos National Laboratory
  • , K.S. VecchioAffiliated withNanoengineering Department, University of California at San Diego
  • , G.J. KusinskiAffiliated withMMFX Technologies CorporationChevron Energy Technology Company

Abstract

Reinforcement bars of microcomposite (MC) steel, composed of lath martensite and minor amounts of retained austenite, possess improved strength and corrosion characteristics over low-carbon (LC) steel rebar; however, their performance under shear loading has not previously been investigated at the microstructural level. In this study, LC and MC steel cylinders were compression tested, and specimens machined into a forced-shear geometry were subjected to quasi-static and dynamic shear loading to determine their shear behavior as a function of the strain and strain rate. The as-received and sheared microstructures were examined using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Higher-resolution microstructural examinations were performed using transmission electron microscopy (TEM). The influence of the starting microstructure on the shear behavior was found to depend strongly on the strain rate; the MC steel exhibited not only greater strain-rate sensitivity than the LC steel but also a greater resistance to shear localization with load. In both steels, despite differences in the starting microstructure, post-mortem observations were consistent with a continuous mechanism operating within adiabatic shear bands (ASBs), in which subgrains rotated into highly misoriented grains containing a high density of dislocations.