Novel growing intermediate phases in Ni/Al diffusion-reaction couples

A. URRUTIA; S. TUMMINELLO; S. SOMMADOSSI

Pula

Encuentro; TOFA 2012 DISCUSSION MEETING ON THERMODYNAMICS OF ALLOYS Pula, Croatia 23-28, September, 2012; 2012

National Research Council– Institute for Energetics and Interphases (CNR-IENI) / DCCI - University of Genoa

The Ni-Al system has been intensively studied since several years because its intermediate phases (IP) presented interesting properties from basic and technological point of view [1]. There is a wide range of industrial applications for these IPs, from corrosion withstanding coatings to turbine blades. The formation of Al-Ni IPs is analyzed in the multilayer system obtained by means of Transient Liquid Phase Bonding (TLPB) process [2]. Therefore this work presents the kinetic and physicochemical characterization of the growing IPs layers of the Ni/Al couples between 720 to 1170ºC, in particular the Ni-rich side. The results showed the presence of 5 IPs layers instead of the 4 predicted by the equilibrium phase diagram [3]: C1: Al3Ni, C2: Al3Ni2, C3: AlNi-rich, C4: AlNi-poor y C5: AlNi3. In accordance with the findings of others authors [4-6], this additional layer C4 may correspond to Al4Ni3. Interdiffusion coefficients for the growth of this layers and microhardness values are also reported and discussed. Reference [1] Miracle, D. Acta metall. mater. 41, 3 (1993) 649-684. [2] Gale W F, Butts D A. Sci. and Tech. of Welding and Joining. 9-4 (2004) 283-300. [3] Okamoto, H. ASM Internacional, Materials Park Ohio. (2002). [4] López G A, Sommadossi S, Zieba P, Gust W, Mittemeijer E J. Mater. Chem. Phys. 78 (2003) 459-463. [5] Ellner M, Kek S, Predel B. J. Less-Common Met. 154 (1989) 207-215 [6] Shoo U., Hirscher M., Mehrer H. Defect and diffusion forum. 143-147 (1997) 631-636.