Experimental parameters influencing grain refinement and microstructural evolution during high-pressure torsion

Abstract Pure nickel was selected for a detailed investigation of the experimental parameters influencing grain refinement and microstructural evolution during processing by high-pressure torsion (HPT). Samples were examined after HPT using microhardness measurements, transmission electron microscopy and orientation imaging microscopy. Processing by HPT produces a grain size of ~170 nm in pure Ni, and homogeneous and equiaxed microstructures are attained throughout the samples when they are subjected to at least ~5 whole revolutions under applied pressures of at least ~6 GPa. For these conditions, the distributions of grain boundary misorientations are similar in the center and at the periphery of the samples. A simple model is proposed to explain the development of a homogeneous microstructure in HPT.

[1]  Terence G. Langdon,et al.  An investigation of microstructural evolution during equal-channel angular pressing , 1997 .

[2]  K. V. Ivanov,et al.  Deformation behavior of Cu-based nanocomposite processed by severe plastic deformation , 2001 .

[3]  R. Valiev,et al.  Thermal evolution of high-purity and boron-doped sub-microcrystalline Ni3Al produced by severe plastic deformation , 1999 .

[4]  R. Valiev,et al.  Bulk nanostructured materials from severe plastic deformation , 2000 .

[5]  Hyoung-Seop Kim,et al.  Finite element analysis of high pressure torsion processing , 2001 .

[6]  R. Valiev,et al.  Paradox of Strength and Ductility in Metals Processed Bysevere Plastic Deformation , 2002 .

[7]  T. Langdon,et al.  Grain refinement of pure nickel using equal-channel angular pressing , 2002 .

[8]  R. Valiev,et al.  Microhardness and microstructural evolution in pure nickel during high-pressure torsion , 2001 .

[9]  R. Valiev,et al.  Low-temperature superplasticity in nanostructured nickel and metal alloys , 1999, Nature.

[10]  G. Korznikova,et al.  The mechanism of nanocrystalline structure formation in Ni3Al during severe plastic deformation , 2001 .

[11]  R. Valiev,et al.  Influence of severe plastic deformation on structure and phase composition of carbon steel , 1994 .

[12]  David J. Smith,et al.  An investigation of grain boundaries in submicrometer-grained Al-Mg solid solution alloys using high-resolution electron microscopy , 1996 .

[13]  R. Valiev,et al.  Plastic deformation of alloys with submicron-grained structure , 1991 .

[14]  T. Langdon,et al.  Factors influencing the equilibrium grain size in equal-channel angular pressing: Role of Mg additions to aluminum , 1998 .

[15]  J. Szpunar,et al.  Orientation imaging microscopy for the study on high temperature oxidation , 2001 .

[16]  T. Langdon,et al.  Orientation imaging microscopy of ultrafine-grained nickel , 2002 .

[17]  David J. Smith,et al.  Fabrication and thermal stability of a nanocrystalline Ni–Al–Cr alloy: Comparison with pure Cu and Ni , 1999 .

[18]  R. Valiev,et al.  Investigations and applications of severe plastic deformation , 2000 .

[19]  R. Kužel,et al.  Thermal stability of submicron grained copper and nickel , 1997 .

[20]  D. Field.  Recent advances in the application of orientation imaging , 1997 .

[21]  R. Valiev,et al.  High-strain-rate superplasticity from nanocrystalline Al alloy 1420 at low temperatures , 2001 .

[22]  N. Xu,et al.  Growth of diamond films on Si3N4 coated silicon substrates , 1996 .

[23]  R. Valiev,et al.  Structure and deformaton behaviour of Armco iron subjected to severe plastic deformation , 1996 .

[24]  V. Stolyarov,et al.  A two step SPD processing of ultrafine-grained titanium , 1999 .

[25]  Ruslan Z. Valiev,et al.  Deformation behavior of nanostructured aluminum alloy processed by severe plastic deformation , 2001 .

[26]  Terence G. Langdon,et al.  The process of grain refinement in equal-channel angular pressing , 1998 .

[27]  D. Brandon,et al.  The structure of high-angle grain boundaries , 1966 .

[28]  N. Tsuji.  Ultrafine Grained Steels , 2002 .

[29]  R. Valiev,et al.  Structure and properties of ultrafine-grained materials produced by severe plastic deformation , 1993 .

[30]  V. Stolyarov,et al.  Mechanical Behavior and Superplasticity of a Severe Plastic Deformation Processed Nanocrystalline Ti-6Al-4V Alloy , 2001 .

[31]  R. Valiev,et al.  TEM/HREM observations of nanostructured superplastic Ni3AI , 2001 .