Effect of boundary conditions on the evolution of lattice strains in a polycrystalline austenitic stainless steel

Abstract

The effect of boundary conditions (constant load, constant strain and elastic follow-up) on lattice strain evolution during creep in a polycrystalline austenitic stainless steel was studied using in situ neutron diffraction at 550°C. The lattice strains were found to remain constant under constant load control. However, under constant strain and elastic follow-up control, the lattice strains relaxed the most in the elastically softest lattice plane {200} and the least in the elastically stiffest lattice plane {111}. The intergranular stresses created between different grain families were constant during creep tests irrespective of the boundary conditions with the initial applied stresses of 250 MPa.

Probing deformation mechanisms of a FeCoCrNi high-entropy alloy at 293 and 77 K using in situ neutron diffraction

“…2a and 2b, respectively. The uncertainties in the measured internal strains were approximately 30 microstrain[40].…”

The effect of cyclic-loading generated intergranular strains on the creep deformation of a polycrystalline material

“…al. [23] measured the evolution of lattice strains during creep dwells under different elastic-follow-up factors and found that under constant load control, the lattice strains in different grain families remained constant.…”

An in situ thermo-mechanical rig for lattice strain measurement during creep using neutron diffraction

“…However, as shown in Ref. 26, when the product of the relaxed lattice strain and the corresponding diffraction elastic constant were determined, it was found that stresses on the different crystal planes relaxed the same amount, and the trends in the relaxation of the lattice stresses agreed with the macroscopic stress relaxation. It should be noted that the DEC used in Ref.…”

“…It should be noted that the DEC used in Ref. 26 were obtained from the unloading stage rather than the loading up stages presented in the current work. More scientific discussion about the results can be found in Ref.…”

“…Experiments were conducted using an ex-service plus further laboratory aged type 316H austenitic stainless steel supplied by EDF energy. 26 Uniaxial samples were manufactured using this material, inserted into the new test machine and the test machine installed into the diffractometer, as explained earlier. Two samples were tested, one with Z ∼ 1.2 and the other with Z ∼ 10.5.…”