Microstructure evolution, texture development, and mechanical properties of hot-rolled 5052 aluminum alloy followed by annealing

Aluminum alloys, especially the 5000 series, have drawn the attention of the transportation industry due to their lightweight and consequently reduced fuel consumption. In this regard, one of the major problems of this alloy is its low strength and ductility that can be solved using rolling and post-annealing. Accordingly, the present study concentrates on this issue. Microstructural images showed that the rolling process develops a lot of tangled and trapped dislocations in the sample, which gradually lead to the formation of dislocation bundles and networks. Subsequent annealing can produce a more homogeneous structure with clear grain boundaries and low dislocation density in the inner region of the grains. However, grain refinement efficiency through rolling is retained even after annealing. Initial and rolled Al5052 with the maximum intensity of 2.87 and 6.33 possess the lowest and highest overall texture. Also, post-annealing decreases the texture intensity to 6.33 and 4.87 at 150 and 200 °C, respectively. In this context, deformation texture components strengthen considerably after the rolling process due to the formation of shear bands, and they slightly weaken during heat treatment. Although the initial annealing of the as-received material does not cause discontinuous recrystallization during rolling, it may facilitate the material recovery before rolling. Post-annealing was found to decrease the improved effect of strength by rolling and increase the negative influence of ductility due to the inhibition of dislocation strengthening. The results showed that both dislocation density and the precipitation of Mg atoms are influential for electrical resistivity

Assessment of severe plastic deformation processes in bulk nanostructured metallic glass

Themetallic glasses areknownasamorphous andmetastablematerials. Thesematerials Q7 have superior mechanical properties over crystalline materials with the same chemistry. Continuous efforts were made to improve the properties of metallic glass. The severe plastic deformation (SPD) method is used to improve the ductility of the glass. SPD causes the deformation at the atomic level in the disordered structure of the glass. Many methods are reported, such as cryogenic cycling, high-pressure torsion, and equal channel angular pressing, which are used for the SPD. In recent works on nanostructured metallic glasses, it has been evidenced that some properties, for example, mechanical, thermal, and magnetic, have improved compared to the bulk metallic glass. This paper has reviewed the recent progress in the SPD of the bulk and nanostructured metallic glasses. Different methods for the SPD have been addressed here. The effect of SPD on the properties of metallic glass is deliberated in this paper. Moreover, the challenging tasks of deformation occurrence in the glass and its characterization were considered, trying to develop a sound understanding of SPD in bulk and nanostructured metallic glasses

Functionally graded titanium implants: Characteristic enhancement induced by combined severe plastic deformation

Commercially pure titanium was processed by equal channel angular pressing (ECAP) and surface mechanical attrition treatment (SMAT) for the purpose of developing functionally graded titanium used for implants and a gradient structure including nanostructured, deformed and undeformed zones were produced on the samples. In particular, it was aimed to design the gradient-structure in the titanium with enhanced properties by applying 4 ECAP passes to form bulk structure of ultrafine-grains and subsequently subjecting SMAT to the surface of ECAPed samples to produce nanostructured surface region. Microstructural examination was made by electron back scatter diffraction (EBSD). Also, microhardness, nanoindentation, topography, roughness and wettability were evaluated. To examine the biological response, human osteosarcoma cells were cultured in contact with the samples in various time periods and morphology change, cell viability and alkaline phosphate activity were conducted also cell morphology was monitored. EBSD showed development of ultrafine-grained structure after 4 passes of ECAP with an average grain size of 500 nm. Applying SMAT resulted in additional refinement in the ECAP samples, particularly in the subsurface regions to a depth of 112 μm. Furthermore, the SMATed samples showed an enhancement in roughness, wettability and hardness magnitudes. Viability enhanced up to 7% in SMATed + ECAPed sample, although the acceptable cell adhesion, improved cell differentiation and mineralization were seen. The combined use of ECAP and SMAT has shown a good potential for optimizing the design of modern functionally graded medical devices and implants

Strain uniformity footprint on mechanical performance and erosion-corrosion behavior of equal channel angular pressed pure titanium

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure, mechanical, and erosion-corrosion behavior of commercial pure (CP) titanium was investigated through experimental work. Four passes of ECAP processing at 400 ℃ was performed on CP titanium. The results showed that the homogeneous structure and coarse equiaxed grains of the initial annealed sample are transformed into the combination of UFG and NS with an average size of 750 nm and 85 nm, respectively. Also, ECAP pass numbers increase the fraction of high angle grain boundaries which improves the ductility of the processed sample. The highest hardness and strength improvement rate was observed after the first pass. Furthermore, the increasing rate of hardness and strength is gradually decreased at the subsequent passes and reached the steady-state level at the 4th pass. This is due to the balance between hardening by dislocations and twinnings accumulation and softening by recovery mechanisms. As a result, a uniform hardness distribution on both the cross-sectional and longitudinal planes is achieved. It was confirmed that erosion-corrosion resistance of the processed sample is enhanced due to the grain refinement, material homogeneity, and quick formation of a strong oxide bond layer on the surface

Nano-Modified Titanium Implant Materials: A Way Toward Improved Antibacterial Properties

Titanium and its alloys have superb biocompatibility, low elastic modulus, and favorable corrosion resistance. These exceptional properties lead to its wide use as a medical implant material. Titanium itself does not have antibacterial properties, so bacteria can gather and adhere to its surface resulting in infection issues. The infection is among the main reasons for implant failure in orthopedic surgeries. Nano-modification, as one of the good options, has the potential to induce different degrees of antibacterial effect on the surface of implant materials. At the same time, the nano-modification procedure and the produced nanostructures should not adversely affect the osteogenic activity, and it should simultaneously lead to favorable antibacterial properties on the surface of the implant. This article scrutinizes and deals with the surface nano-modification of titanium implant materials from three aspects: nanostructures formation procedures, nanomaterials loading, and nano-morphology. In this regard, the research progress on the antibacterial properties of various surface nano-modification of titanium implant materials and the related procedures are introduced, and the new trends will be discussed in order to improve the related materials and methods

Tailoring twist extrusion process; the better strain behavior at the lower required loads

This study dealt with discovering the optimal conditions of the twist extrusion parameters for producing materials possess enhanced strain behavior with the least amount of extrusion load. It was found that the twist angle has a dominant influence on the strain behavior of the deformed sample with the contribution percentage of 56%, while the effect of friction coefficient would be the most noticeable if the required extrusion load is considered. Based on above, pure copper with the square cross-section was subjected to the process with the large twist angle at the best lubricant state. The results showed that the strength and hardness of the deformed copper were considerably enhanced compared to the initial condition due to the substantial grain refinement. The uniform plastic deformation zone of the deformed sample is limited which causes the reduction of strain-hardening exponent and ductility. Moreover, the lateral region of the sample's cross-section endures larger plastic strain compared to the central one, leading to owning higher hardness. A combined microstructure consisting of low angle dislocation walls and high angle grain boundaries was also determined for the deformed copper. © 2020 Elsevier B.V

Biomedical Application

Equal channel angular pressing method is one of the prominent severe plastic deformation techniques to obtain ultrafine grained and even nanostructured metals and alloys by imposing intense plastic strain. As known, pure titanium can be a suitable candidate for biomedical applications because it does not release any toxic ions into the body fluids and also, its biocompatibility properties. The present investigation deals the corrosion behavior of commercial pure titanium before and after ECAP process up to 10 passes by route BC at the 250 degrees C in the 0.9% NaCl solution. The electrochemical results revealed that the corrosion resistance of titanium sample is improved by adding pass number because of the fabrication of passive oxide layer on the surface of the material. It is found that about 92% reduction at the corrosion rate magnitude and also, approximately 41% improvement at the hardness value have been achieved at the final pass as compared to the annealed condition. Furthermore, it is observed that the passive film on the surface of final pass sample is dense and integral with uniform structure, while the as-received one has some rarefactions and does not have very uniform surface

pressing

Equal-channel angular pressing (ECAP) is a prominent technique that imposes severe plastic deformation into materials to enhance their mechanical properties. In this research, experimental and numerical approaches were utilized to investigate the mechanical properties, strain behavior, and damage prediction of ECAPed 7025 aluminum alloy in various conditions, such as die channel angle, outer corner angle, and friction coefficient. Experimental results indicate that, after the first pass, the yield strength, ultimate tensile strength, and hardness magnitude are improved by approximately 95%, 28%, and 48.5%, respectively, compared with the annealed state, mainly due to grain refinement during the deformation. Finite element analysis shows that the influence of die channel angle is more important than that of outer corner angle or friction coefficient on both the strain behavior and the damage prediction. Also, surface cracks are the main cause of damage during the ECAP process for every die channel angle except for 90A degrees; however, the cracks initiated from the neighborhood of the central regions are the possible cause of damage in the ECAPed sample with the die channel angle of 90A degrees

pressing process

Ultrafine grained materials have experienced a rapid development during the last two decades. Constrained groove pressing (CGP) process is one of the severe plastic deformation methods to fabricate ultrafine grain sheet materials. In this research, wear behavior of brass sheet subjected to CGP process was investigated. Generally it is shown that CGP process enhances the wear resistance of the material and this behavior is improved by increasing pass number. Also, the effect of initial pass and lower applied normal load on the wear resistance is more profound than subsequent passes and higher applied normal load, respectively. In addition, the influence of normal load is more profound than pass number at the increment of friction force. Although CGP process results in reduction at the specific wear rate, the influence of the first pass is much higher than the subsequent ones. Furthermore, lower specific wear rate is occurred at the higher applied normal load. The scanning electron microscopy analyses indicated that the wear mechanism is transferred from adhesion, delamination, abrasion and oxidation for the annealed condition to abrasion and adhesion for the third pass CGP sample. Also, it is found that there is a reverse relationship between specific wear rate and hardness. (C) 2014 Elsevier Ltd. All rights reserved

A brief review on the evolution of metallic dental implants: history, design, and application

In recent years, significant advances in the field of medical materials have begun to emerge, especially in the nanotechnology. The modern area of nanostructured implants possesses wide applications in various medical implants including its dental use. Nano-surface functions present substantial resolutions to medical obstacles through improved biomaterial proficiency, innovative dental-implant designs, and surface design procedures, such as nanoscale adhesive surfaces, bio-chemical anodization, and surface modification technique. This work covers dental implant history, nanotechnological advances and its development and includes a description, basic properties, and the related results of composites and surface morphology, and the different types of nanomaterials used in dental implants. Significant attempts have been made over the last few decades to strengthen the osteointegration and to prevent bacterial attachment to the implant surfaces. The micro and nano-topography of the hierarchical surface orchestrate the biological reactions of implants and may solve the problems associated with implant-tissue issues. This research offers a brief description of the nanostructured biomaterials to enhance dental implants’ performance and may open new frontiers in the advancement of implant technology