SIPS 2018

DETAILLED PROGRAM OVERVIEW

Diffusive and Displacive Phase Transformations Driven by High Pressure Torsion
Boris Straumal¹; Askar Kilmametov²; Olga Kogtenkova³; Andrey Mazilkin²; Brigitte Baretzky²;
¹INSTITUTE OF SOLID STATE PHYSICS RAS, Chernogolovka, Russian Federation; ²KARLSRUHE INSTITUTE OF TECHNOLOGY (KIT), Eggenstein-Leopoldshafen, Germany; ³INSTITUTE OF SOLID STATE PHYSICS, Chernogolovka, Russian Federation;
PAPER: 302/SISAM/Invited (Oral)
SCHEDULED: 14:25/Mon./Copacabana A (150/1st)

ABSTRACT:
The influence of high pressure torsion (HPT) on the diffusive and displacive phase transformations in sustainable advanced materials has been studied. In diluted Cu-based binary alloys the HPT drives the competition between deformation-driven precipitation and dissolution of precipitates. The dynamic equilibrium between these two processes is reached already after 1.5-2 anvil rotations. The composition of Cu-matrix in this equifinal state is equal to that which can be reached in equilibrium after long annealing at a certain temperature Teff. Teff in diluted Cu-based binary alloys increases with increasing activation enthalpy of diffusion of a second component and its melting temperature Tm [1, 2]. In Cu-Al-Ni shape memory alloys, HPT leads to the combination of displacive (austenite-martensite) and diffusive (decomposition of supersaturated solid solution) phase transitions. On the one hand, the HPT of these alloys led to the precipitation of α1-phase in the Al-pure alloy and to the precipitation of γ1-phase in the Al-rich one (as if they were annealed at an effective temperature Teff = 620-20°C). As a result of this precipitation, the matrix in the first alloy was enriched and in the second one depleted in Al. The resultant composition change in the Cu-rich matrix changed also the route for the martensitic transformations. After HPT, both alloys contained mainly β'3 martensite with a certain amount of γ'3 martensite. Thus, the HPT-driven diffusive transformations (precipitation of α1- and γ1-phase) influence the followed displacive (martensitic) transformation [3]. The combination of displacive and diffusive phase transitions has been observed also under HPT of Ti-Fe and Ti-Co alloys [4].

References:
[1] B.B. Straumal, V. Pontikis, A.R. Kilmametov, A.A. Mazilkin, S.V. Dobatkin, B. Baretzky, Acta Mater. 122 (2017) 60-1.
[2] B.B. Straumal, A.R. Kilmametov, A. Korneva, A.A. Mazilkin, P.B. Straumal, P. ZiA�ba, B. Baretzky, J. Alloys Comp. 707 (2017) 20-26.
[3] B.B. Straumal, A.R. Kilmametov, G.A. Lopez, I. Lopez-Ferrero, M.L. No, J. San Juan, H. Hahn, B. Baretzky, Acta Mater. 125 (2017) 274-285.
[4] A. Kilmametov, Yu. Ivanisenko, A.A. Mazilkin, B.B. Straumal, A.S. Gornakova, O.B. Fabrichnaya, M.J. Kriegel, D. Rafaja, H. Hahn, Acta Mater. 144 (2018) 337-351.