On the generation of microstrains during the plastic deformation of Waspaloy

Neutron diffraction has been used to characterize the development of micros trains during the plastic deformation of the polycrystalline nickel-base al loy, Waspaloy. Two types of experiment were per formed: (i) in situ tensile resting on the diffracrometer to determine the response parallel and perpe ndicular to the loading direction and (ii) measurement of the orientation d ependence of the microstrain accumulation using a Eulerian cradle. Large re sidual microstrains are shown to develop. Along the loading direction, thes e are typically tensile in the gamma' phase and compressive in the gamma ph ase; however, the values are sensitive to both the orientation of the diffr acting crystallite and the amount of plastic deformation of the material. T he behaviour is due to the differential deformation between grains in diffe ring orientations (intergranular microstresses) and the two phases (interph ase microstresses). It is shown that at low bulk plastic strains, intergran ular microstresses develop rapidly, whilst at larger plastic strains the mi crostresses arising from interphase interactions become dominant. These eff ects have implications for the determination of residual stresses using dif fraction-based techniques and these are discussed. (C) 1999 Acta Metallurgi ca Inc. Published by Elsevier Science Ltd All rights reserved.