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Diffusive and Displacive Phase Transformations in Nanocomposites under High Pressure Torsion

Straumal B., Kilmametov A., Gornakova A., Mazilkin A., Baretzky B., Korneva A., Zięba P.

Archives of Metallurgy and Materials

2019

Vol. 64, iss. 2

457--465

The high-pressure torsion (HPT) of Ti-Fe alloys with different iron content has been studied at 7 GPa, 5 anvil rotations and rotation speed of 1 rpm. The alloys have been annealed before HPT in such a way that they contained different amounts of α/α' and β phases. In turn, the β phase contained different concentration of iron. The 5 anvil rotations correspond to the HPT steady-state and to the dynamic equilibrium between formation and annihilation of microstructure defects. HPT leads to the transformation of initial α/α' and β-phases into mixture of α and high-pressure ω-phase. The α → ω and β → ω phase transformations are martensitic, and certain orientation relationships exist between α and ω as well as β and ω phases. However, the composition of ω-phase is the same in all samples after HPT and does not depend on the composition of β-phase (which is different in different initial samples). Therefore, the martensitic (diffusionless) transformations are combined with a certain HPT-driven mass-transfer. We observed also that the structure and properties of phases (namely, α-Ti and ω-Ti) in the Ti – 2.2 wt. % Fe and Ti – 4 wt. % Fe alloys after HPT are equifinal and do not depend on the structure and properties of initial α'-Ti and β-Ti before HPT.

Phase transitions in metallic alloys driven by the high pressure torsion

Straumal B., Korneva A., Zieba P.

Archives of Civil and Mechanical Engineering

2014

Vol. 14, no. 2

242--249

Severe plastic deformation can lead to the phase transformations in the materials. Even the severe plastic deformation at ambient temperature is frequently equivalent to the heat treatment at a certain elevated temperature (effective temperature). However, if the real annealing at the elevated temperature leads to the grain growth, the severe plastic deformation leads to strong grain refinement. In this review the methods of determination of effective temperature after high-pressure torsion of metallic alloys are discussed.

Microstructure and magnetic properties of Cu-Co alloys after high pressure torsion

Korneva A., Kogtenkova O., Protasova S., Straumal B., Mazilkin A., Kurmanaeva L., Zięba P.

Inżynieria Materiałowa

2013

Vol. 34, nr 4

306--309

The microstructure and magnetic properties of binary Cu-Co alloys are studied. The investigations have been carried out using samples in two structural states, i.e. as-cast and after severe plastic deformation by the high-pressure torsion (HPT). HPT carried out at the ambient temperature and pressure of 6 GPa. The grain size after HPT is in the nanometer range. HPT allows one to control the ratio between ferromagnetic and superparamagnetic precipitates in the diamagnetic matrix.

Badano mikrostrukturę i właściwości magnetyczne stopów Cu-Co zawierających 2,2 oraz 4,9% mas. Co. Badania przeprowadzono na próbkach w dwóch stanach strukturalnych, tj. odlewanych i po intensywnym odkształceniu plastycznym przez skręcanie pod wysokim ciśnieniem (HPT). HPT przeprowadzono w temperaturze otoczenia pod ciśnieniem 6 GPa. Uzyskany rozmiar ziaren był rzędu nanometrów. Wyniki pomiarów namagnesowania wykazały, że HPT pozwala kontrolować proporcję między ferromagnetycznymi i superparamagnetycznymi wydzieleniami w matrycy diamagnetycznej.