J. Phys. IV France
Volume 112, October 2003
Page(s) 1067 - 1070

J. Phys. IV France
112 (2003) 1067
DOI: 10.1051/jp4:20031066

Martensitic transformation and ordering in heat-resistant Ni-Co-Cr-AI $\beta$/ $\gamma$ eutectics

S.V. Kositsyn1, N.V. Katayeva1, I.I. Kositsyna1, A.I. Valiullin1 and V.S. Litvinov2

1  Institute of Metal Physics, Ural Branch RAS, Laboratory of Mechanical Properties, 18 S. Kovalevskaya Str., Ekaterinburg 620219, Russia
2  Ural State Technical University, 2 Mir Str., Ekaterinburg 620002, Russia

The method of thin-foil transmission electron microscopy was used to examine phase transformations in the $\beta$-phase, representing the main heat-resistant component, of $\beta$/ $\gamma$ eutectics of the Ni-Co-Cr-Al system (mass % : 0-15 Co, 14-20 Cr, 8.5-10.5 Al). The martensitic transformation $\beta\rm (B2)\to L1_{0}$ took place in all the alloys, except those with 20 mass % Cr, when they were quenched in water from 1200°C. It was found for the first time that high-rank superstructures A 2B (Ni 2Al) and A 5B 3 (Ni 5Al 3) could be formed in a complex-alloyed $\beta$ solid solution. Phase transformations L1 $_{0}\to\rm A_5B_3$, $\rm L1_0\to 14M$, $\rm L1_0\to B2\to A_2B$, and $\rm L1_0\to B2\to A_5B_3$ were observed in the $\beta$-component of the eutectics when isothennal annealing temperature was increased from 250 to 600°C. At a temperature of 400°C and higher those transformations were accompanied by the decomposition of the $\beta$ solid solution and the appearance of dispersed $\alpha$-Cr particles. Structural features of the aforementioned phase transformations in heat-resistant quaternary eutectics were considered.

© EDP Sciences 2003