Deformation Behavior and Damage Evaluation in a New Titanium Diboride (TiB2) Steel-Based Composite

Deformation behavior and damage evaluation of a new composite steel has been investigated by means of in situ three-point bend tests in the scanning electron microscope. The titanium diboride (TiB2)-reinforced steel composite is produced by in situ precipitation of the TiB2 particles during eutectic solidification. This production process developed by ArcelorMittal leads to a steel composite with a significant increase in specific stiffness (>20%), and good strength/ductility compromise. The microstructures obtained consist of primary TiB2 crystals surrounded by a eutectic mixture of ferrite and TiB2 particles. The primary mode of damage is particle fracture and inhomogeneous plastic deformation in the matrix. In contrast with other production process, particle fracture was more common than interfacial debonding indicating that interfacial strength is not the limiting factor in damage accumulation and fracture in this composite. Crack growth occurred by particle fracture ahead of the crack tip, producing large microvoids, which then link up to the growing crack by ductile failure of the remaining matrix ligaments. The results suggest also that the cracks tended to avoid direct particle interactions.