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Effect of SPD Grain Refinement and Peculiarity of Structure and Mechanical Properties of UFG Ni

Nikolay Krasilnikov ², Witold Łojkowski ³, Ruslan Z. Valiev ²

1. Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, K.Marks St.12, Ufa 450000, Russian Federation
2. Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, K.Marks St.12, Ufa 450000, Russian Federation
3. Polish Academy of Sciences, High Pressure Research Center (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland

Abstract

Effect of SPD grain refinement and peculiarity of structure and mechanical
properties of UFG Ni.

N. Krasilnikov1,2, W. Lojkowski3, R. Valiev1

1Institute of Physics of Advanced Materials, Ufa, Russia
2Ulyanovsk State University, Ulyanovsk, Russia
3High Pressure Research Center, Polish Academy of Sciences, Warsaw,
Poland

The structure and mechanical properties of Ni subjected to different
methods of severe plastic deformation (SPD) are investigated. An
opportunity of obtaining of ultra-fine grain structures (UFG) in Ni
with grain size about 200-300 nm and less is shown. Mechanical test by
means of strain at room temperature reveals high strength in UFG Ni
with s[0.2] more than 1000 MPa and sufficient ductility.
Low-temperature annealing somewhat decreases strength (15%) but
increases ductility more than in 1.5 times.
Large strain degree and high pressure on sample at torsion correspond
to a more homogeneous structure and smaller grain size as compared to
the material obtained by equal-channel angular pressing (ECAP) and
rolling. These structural differences define the peculiarities of
structure and mechanical properties evolution at annealing of SPD Ni.
At annealing temperature 100S UFG Ni transformed to more equilibrium
state without grain growth. Considerable change of structure and
mechanical properties of SPD Ni takes place after annealing at 200S.
This change is greater for nickel after high pressure torsion (HPT)
when the collecting recrystallization, the formation of high
heterogeneity of grain size and great drop of strength were observed.
It is occur due to the big cumulative deformation at torsion and the
large level of non-equilibrium state of HPT structure. Material after
ECAP and rolling possesses greater thermal stability and the grains
remained sub-micron.
The observation of transition from brittle fracture of coarse-grained
Ni to quasi-tough one of UFG Ni proves that deformation mechanism
changes at room temperature and that it is possible to realise
grain-boundary sliding in material after SPD.
Obtaining of high strength Ni with good ductility opens perspectives
of its application in industry particularly for mirco-systems.

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Effect of SPD Grain Refinement and Peculiarity of Structure and Mechanical Properties of UFG Ni

Presentation: poster at E-MRS Fall Meeting 2002, by Nikolay Krasilnikov See On-line Journal of E-MRS Fall Meeting 2002 Submitted: 2003-02-16 17:33 Revised: 2009-06-08 12:55

Presentation: poster at E-MRS Fall Meeting 2002, by Nikolay Krasilnikov
See On-line Journal of E-MRS Fall Meeting 2002

Submitted: 2003-02-16 17:33 Revised: 2009-06-08 12:55