Uday Chakkingal

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.

Formability of aluminum alloys poses a major challenge for their wider application in automotive sheet metal components as the deep drawability of aluminum is low when compared to steel. This is indicated by the low limiting drawability ratio (LDR) of aluminum sheet blanks which is characterized by the poor r value or the plastic strain ratio. Recently, a number of techniques have been attempted to improve the r value of an FCC metal like aluminum by altering the texture. In the present study, a groove pressing process was carried out on commercial purity aluminum sheets under three different orientations to its rolling direction. The r, rm and Δr values of the groove pressed specimens were experimentally determined. Improvements in these values were obtained. X-ray diffraction scans were carried out on the specimens to measure the relative intensities of the (1 1 1) and (2 0 0) peaks in the pattern. The LDR, determined by the Swift cup forming test shows an improvement for the aluminum sheet specimen groove pressed at 0° and 45° to the RD. This can be attributed to the improved r value due to the development of (1 1 1)//ND shear texture imparted to the specimen by groove pressing. © 2010 Elsevier B.V.

Aluminium alloy sheets have poor drawability compared to steel sheets as indicated by the values of the plastic strain ratio or the R value. Because of the textures developed during commercial annealing and cold rolling processes, the R value for aluminium alloys is typically less than 1. Since the R value is heavily influenced by the crystallographic texture in the sheet, processes that develop a favourable texture can be utilised to improve the R value. In this study, a severe plastic deformation process called groove pressing has been used to repeatedly deform sheet specimens of aluminium alloy AA 5052. The R values of groove pressed specimens were experimentally determined. X-ray diffraction scans of the groove pressed specimens were carried out to measure the relative intensities of (111) and (002) peaks in the pattern. The largest increase in the R value was for specimens cut at 90° to the rolling direction and groove pressed to four passes. XRD data indicate that the groove pressing process is capable of introducing a favourable shear texture. © (2013) Trans Tech Publications, Switzerland.

Elasto-plastic finite element analysis was carried out for analyzing the severe plastic deformation behavior of copper specimens during groove pressing. Deformation localization was studied in terms of strain variations along the longitudinal direction. Plastic strain is lower at the local interface between the shear and the flat regions, which receives very little shear during the pressing cycle. Strain localization is more intensified with the number of groove pressing cycles, although the average strain level increases. © 2008 Elsevier B.V. All rights reserved.

There is increasing interest in using Al alloy sheets for auto body applications. However Al alloys exhibit poor drawability as indicated by low values of the normal anisotropy, rm. Techniques for improving the value of rm rely on developing a favourable shear texture in the sheet. In this study, Al alloy AA 6061 sheets of dimensions 225 mm x 200 mm and 1 mm thick were subjected to severe plastic deformation by repeated groove pressing using a set of grooved and flat dies alternatively. The orientation of the grooves with respect to the rolling direction was also varied. Microstructure characterization and mechanical property measurements were carried out. X-ray diffraction scans were carried out to measure the relative intensities of the (111) and (200) peaks. The r values was measured as per ASTM standard E 517 on strip specimens cut at 0° , 45° and 90° to the rolling direction and the normal anisotropy value (rm) and planar anisotropy value (△r) values were determined. The limiting drawing ratio (LDR) was determined using the Swift cupping test techniques. It was observed that the rm values increased from 0.72 in the as received condition to a maximum of 0.94 and the LDR increased from 1.93 to 2.06 when the groove pressing was carried out with grooves at to 45° the rolling direction. The improvement in rm values can be correlated to the texture developing in the sheet as a result of severe plastic deformation. © (2010) Trans Tech Publications.

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.

Commercial purity aluminium was subjected to a severe plastic deformation technique called groove pressing at both room temperature and cryogenic temperatures. In both cases, submicron sized grain structures were obtained after deformation; there was no significant difference in microstructures obtained under room temperature and cryogenic temperature deformation conditions. © 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Commercial pure titanium (cpTi) sheets have been processed by groove pressing (GP) at room temperature to refine the grains so as to improve its properties for bone implant applications. Atomic force microscopy revealed submicron/nano roughness features on the processed cpTi. The contact angle measurements show good wettability and higher surface energy when compared to unprocessed cpTi. The bioactivity of the GP samples in simulated body fluid was also found to be enhanced with the formation of a homogenous and dense globular hydroxyapatite layer. The Ca/P ratio of the apatite layer was around 1.66 as similar to the bone mineral phase. The bioactivity enhancement of GP samples has been related to the submicron grain features which results in an increase in the surface roughness and wettability. © 2009 Elsevier B.V. All rights reserved.

Groove pressing (GP) is a severe plastic deformation technique for producing ultra fine grain sized microstructures in metals and alloys. In the present study, groove pressing and a two-step process of groove pressing followed by cold rolling was used to investigate the potential of these processes to produce ultra fine grained copper with significantly enhanced strength. Mechanical and microstructure properties were evaluated after groove pressing and after groove pressing followed by cold rolling. The advantages conferred by groove pressing prior to cold rolling on producing copper with enhanced properties has been investigated.

Biodegradable Mg–0.6Ca alloy was processed by groove pressing technique to obtain ultrafine-grained structure for orthopedic application. The effect of microstructural variations and surface features produced by groove pressing on the mechanical performance, corrosion resistance, and in-vitro bioactivity in Mg–0.6Ca alloy were investigated. The optical microscopy observation showed that a grain size of 5 µm (compared to 64 µm for annealed sample) was achieved after hot rolling and groove pressing. The results of the tensile test and hardness test indicated that there was enhancement in mechanical properties in the groove pressed (GP) sample (yield strength (YS) = 45.0 ± 3.2 MPa, ultimate tensile strength (UTS) = 124.10 ± 3.40 MPa, hardness = 55.0 ± 1.50 HV) than that of annealed (AN) sample (YS = 20.10 ± 2.40 MPa, UTS = 58.20 ± 3.80 MPa, hardness = 34.0 ± 1.30 HV). The decrease in grain size enhanced the biomineralization with an increase in the hydroxyapatite formation on the surface of the GP sample indicating higher passivation to corrosion. The high surface energy of the GP sample (24.07 ± 3.60 mJ/m2) than AN sample (45.14 ± 1.0 mJ/m2) indicated higher wettability of GP samples. The immersion and electrochemical tests indicated an improvement in corrosion resistance of the GP sample. Also the hydrogen evolution test showed a lower hydrogen evolution for the GP sample.