INFLUENCE OF INTERFACE ORDERING ON THE THERMOMECHANICAL PROPERTIES OFOXIDE-METAL SCALE

The relation between Ni-ions ordering and the development of growth an d residual stresses at the Ni/NiO interface is studied. The crystallog raphic structure of the 3D Ni/NiO interface is proposed to be two-laye red with the space group P4/mmm. Calculated strain-internal elastic st ress dependencies reveal thermal growth regimes with a first-order pha se transition resulting in the duplex structure of the interface: the ordered lower layer coherent with the substrate, End the upper layer i ncoherent with the lower one. Numerical modeling of the corresponding growth and residual stresses is performed using two mechanical models. If the new oxide layer in the upper part grows independently of the l ayers already formed, then the calculated growth stresses after relaxa tion vary from 0 to - 250 MPa with the thickness of the lower layer, a nd the residual stresses vary from -600 to -850 MPa. When the new oxid e layer is initially stressed, the variation of the growth stresses is from 520 to - 280 MPa. The residual stresses vary from -80 to -880 MP a in this case.