Commercial purity copper sheets were subjected to a severe plastic deformation technique called groove pressing (GP) to a strain of 3.48 at both room and cryogenic temperatures. The mechanical properties and microstructure were studied as a function of the number of passes. A deformed microstructure with cell sizes approximately 0.5 μm in size were obtained from a starting annealed grain size of 78 μm. © 2005 Elsevier B.V. All rights reserved.

Chakkingal Uday

Department of Metallurgical and Materials Engineering

P. Venugopal

Cryogenics

Grain size and shape

METAL PRESSING

Metallographic microstructure

Optical microscopy

Plastic deformation

Strain

Thermal effects

Transmission electron microscopy

Cryogenic temperatures

GROOVE PRESSING (GP)

Severe plastic deformation

Copper

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IIT Madras

Materials Science and Engineering A

In the present work, cold rolling and cryo-rolling were performed on 99% commercially pure copper substrates. Both cold and cryo-rolling processes caused severe plastic deformation that led to an increase in dislocation density by 14× and 28× respectively, as compared to the pristine material. Increases in average tensile strengths, by 75% (488 MPa) and 150% (698 MPa), were observed in the two rolled materials as the result of the enhancement in dislocation density. In addition to strength, enhanced antibacterial property of cryo-rolled copper was observed in comparison to cold rolled and pristine copper. Initial adhesion and subsequent proliferation of bio-film forming Gram-positive bacteria Staphylococcus aureus was reduced by 66% and 100% respectively for cryo-rolled copper. Approximately 55% protein leakage, as well as ethidium bromide (EtBr) uptake, were observed confirming rupture of cell membrane of S. aureus. Inductively coupled plasma-mass spectroscopy reveals higher leaching of elemental copper in nutrient broth media from the cryo-rolled copper. Detailed investigations showed that increased dislocation led to leaching of copper ions that caused damage to the bacterial cell wall and consequently killing of bacterial cells. Cryo-rolling enhanced both strength, as well as antibacterial activity, due to the presence of dislocations. © 2018 by the authors.

Fulltext

Materials

Relationship between dislocation density and antibacterial activity of cryo-rolled and cold-rolled copper

Among several existing and well established severe plastic deformation techniques, constrained groove pressing (CGP) is one of the prominent and trusted routes for producing ultrafine grained materials. In the present work medical grade 316L austenitic stainless steel sheet of 3 mm thickness was subjected to CGP up to two cycles. Samples obtained as a result of processing were investigated both experimentally and numerically through finite element (FE) analysis using DEFORM-3D software. XRD study revealed the transformation of austenitic phase to martensitic phase. Tensile and hardness tests were conducted to see the effect of processing on mechcanical properties. The ultimate tensile strength increases with the number of CGP passes from 767 (solution annealed) to 1162 MPa (after 2 cycles), similarly, yield strength increases from 269 (as received) to 328 MPa (after 2 cycles). Finite element analysis showed an imposed strain of 2.30 with standard deviation of 0.31 after two cycle of CGP is in coordination with experimental measured strain of 2.32. © 2019 Trans Tech Publications Ltd, Switzerland.

Materials Science Forum

Numerical analysis of constrained groove pressing and mechanical behaviour of processed 316l stainless steel

Constrained groove pressing (CGP) is one of the severe plastic deformation techniques to achieve ultrafine grains in bulk sheet metals. The CGP process induces large plastic strain through incremental steps of shear and reverse shear using grooved and flat dies. The equivalent plastic strain distribution during CGP process can be correlated to the extent of grain refinement and the uniformity of ultrafine grains. The numerical analysis in the past have assumed isotropic hardening to model CGP process that does not consider the Bauschinger effect due to continuous change in deformation path between subsequent stages. In the present work, the effect of Bauschinger effect is considered using a combined isotropic-kinematic hardening model in simulation. The finite element model assuming isotropic hardening is validated with the results available in literature. Experiments on CGP were performed using three different materials and were modelled using both isotropic and combined hardening models. The maximum strain and the strain inhomogeneity predicted using combined hardening models were consistently greater than the isotropic hardening assumption. © 2018

Journal of Manufacturing Processes

Accounting Bauschinger effect in the numerical simulation of constrained groove pressing process

Metallic materials are widely studied for load-bearing applications such as orthopaedic implants. Titanium and its alloys find applications for load-bearing medical implants due to their biocompatibility, good corrosion resistance, high specific strength and good bioadhesion. However, the bioactivity of titanium which can be defined as the ability to form a hydroxyapatite (HA) layer, which is similar to the mineral phase of the bone, on its surface when in contact with the biological environment is poor. On the other hand, magnesium and its alloys are becoming the prime choice for degradable biomaterials targeted for temporary applications in cardiac and orthopaedic fields. However, controlling the degradation rate is the essential issue in developing magnesium-based biomaterials. Synthesis of nano/ultra fine grain materials to enhance the biofunctionalisation of orthopaedic implants is of considerable interest as cells live in a nano-featured environment consisting of a complex mixture of pores and fibres of the extracellular matrix. Recently severe plastic deformation (SPD) processes which can achieve considerable grain refinement, typically to the submicrometre or nanometre level, have gained significant attention in materials research. Therefore, using SPD processes to develop grain-refined titanium and magnesium-based materials for implant applications has become a promising strategy in developing new-generation medical materials. Particularly for titanium, nanostructuring results in improved mechanical properties and increased bioactivity. Whereas for magnesium, grain refinement results in controlled degradation due to higher biomineralisation with enhanced tissue response. The present review aims to provide a comprehensive summary of the progress achieved using SPD processes in developing nano/ultra fine grain structured titanium and magnesium for implant applications. Role of smaller grain size on enhancing bioproperties is also discussed including the challenges involved in processing to achieve the grain refinement up to nano/ultra fine grain level. © 2016 Informa UK Limited, trading as Taylor &amp; Francis Group.

Materials Technology

Nano and ultra fine grained metallic biomaterials by severe plastic deformation techniques

Groove pressing (GP) has been successfully adopted to achieve fine grain size up to 7 μm in AZ31 magnesium alloy with an initial grain size of 55 μm. The effect of microstructural evolution and surface features on wettability, corrosion resistance, bioactivity and cell adhesion were investigated with an emphasis to study the influence of deposited phases when the samples were immersed in simulated body fluid (SBF 5 ×). The role of microstructure was also evaluated without any surface treatments or coatings on the material. GPed samples exhibit improved hydrophilicity compared to the annealed sample. After immersion in SBF, specimens were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) analysis and X-ray diffraction (XRD) methods. More amount of white precipitates composed of hydroxyapatite and magnesium phosphate along with magnesium hydroxide was observed on the surfaces of groove pressed specimens as compared to the annealed specimens with an increase in immersion time in SBF. Corrosion behavior of the samples estimated using potentiodynamic polarization curves indicate good corrosion resistance for GPed samples before and after immersion in SBF. The MTT assay using rat skeletal muscle (L6) cells revealed that both the processed and unprocessed samples are nontoxic and cell adhesion was promising for GPed sample. © 2013 Elsevier B.V. All Rights Reserved.

Materials Science and Engineering C

Role of biomineralization on the degradation of fine grained AZ31 magnesium alloy processed by groove pressing

Engineering and commercialization of equal channel angular extrusion (ECAE)

Materials Science and Engineering: A

Development of repetitive corrugation and straightening

Scripta Materialia

Effect of deformation temperature on the microstructure developed in commercial purity aluminum processed by equal channel angular extrusion

The effect of strain path and temperature on the microstructure developed in copper processed by ECAE

Equal-channel angular pressing using plate samples

Applicability of the groove pressing technique for grain refinement in commercial purity copper

Journal	Materials Science and Engineering A
ISSN	09215093
Open Access	No