PHASE-FORMATION AND INTERDIFFUSION IN AL-CLAD-430 STAINLESS-STEELS

Diffusion annealing treatments were carried out with Al-clad 430 stain less steels for the development of diffusion structures and characteri zation of interdiffusion of Fe, Cr, and Al. The treatments included is othermal anneals at 600 degrees C for various times with thin foils of 430Y and 430 stainless steels roll-clad with 1100 Al. A two step anne aling treatment in which the foils were initially annealed at 600 degr ees C followed bq a subsequent anneal at 800 degrees C was also invest igated for homogenization of the Al-clad steels. The diffusion structu res of the various foils were examined by SEM-EDS and X-ray diffractio n techniques. The A-clad 430Y and 430 stainless steel foils annealed a t 600 degrees C developed two diffusion layers identified as (Fe, Cr)( 2)A(3) and (Fe, Cr)(2)Al-3 based on composition. Interdiffusion fluxes and integrated interdiffusion coefficients were calculated for these phase layers. The integrated interdiffusion coefficients of Cr, Fe and Al were approximately in the ratios of 1:5:6 and 1:4:5 for the (Fe, C r),AI, and (Fe, Cr)(3)Al-2 phases, respectively. The two-step annealin g treatment at 600 and 800 degrees C resulted in the formation of a ho mogeneous Fe-Cr-Al alloy (bcc) through the foil thickness; the lattice parameter of the alloy was determined to be 2.876 Angstrom. The Al-cl ad 430Y foils developed less porosity than the Al-clad 430 foils durin g the homogenization treatment. (C) 1998 Elsevier Science S.A. All rig hts reserved.