Evolution of internal strains in a two phase zirconium alloy during cyclic loading Original Research Article

In situ cyclic loading experiments were carried out on a hot rolled Zr–2.5 Nb plate material at the ISIS pulsed neutron facility of the Rutherford Appleton Laboratory. The cyclic strain was controlled to a fixed total of ±2.4% and the lattice strain evolutions in both the loading and the Poisson’s directions were monitored by neutron diffraction. Experimental results show that the large Bauschinger effect during reverse loading is caused by a combination of the interphase, intergranular and intragranular stresses. Experimental data were interpreted by a combined finite element method (FEM) and elasto-plastic self-consistent (EPSC) model. An overall good agreement was achieved. However, several discrepancies were seen due to deficiencies with the mechanism of modelling the hardening behaviour during stress reversal. Further improvements require functions that can relate micromechanical properties to the evolution of the intragranular microstructure in a more realistic way.