• Valiev, R.
• Pakieła, Zbigniew
• Krasilnikov, N.
• Łojkowski, Witold

Abstract

<p>It was shown that nickel processed by equal channel angular pressing (ECAP) followed by cold rolling and annealing presents quite unique mechanical properties. This permits to produce in a controlled way nickel samples with high mechanical strength and ductility. Mechanical properties ranged from ultimate tensile stress (UTS) of 1270 MPa, with elongation to rupture of about 6%, to UTS of 900 MPa, and elongation to rupture up to 12%. The high strength properties of the material result from the additive strengthening contributions of grain boundaries in ultra fine grains and dislocation substructures. The grain boundaries and, in particular, degree of their nonequilibrium state influence primarily ductility and strength of the material. The material was deformed with the formation of shear bands of diameter much larger than the grain size, and it seems that its ductility is connected with a deformation mechanism involving collective relative displacement of grain groups, with extensive grain boundary sliding. The produced high strength Ni with good ductility has a potential for practical applications, particularly, for micro-electro-mechanical systems (MEMS).</p>

Topics

• impedance spectroscopy
• grain
• nickel
• grain size
• grain boundary
• strength
• dislocation
• annealing
• deformation mechanism
• cold rolling
• ductility