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1 – 10 of 191Fauziana Lamin, Ahmad Kamal Ariffin Mohd Ihsan, Intan Fadhlina Mohamed and Cheeranan Krutsuwan Nuphairode
This paper aims to evaluate the validity of bilinear hardening model to represent the stress flow of high-pressure torsion (HPT)-strengthened lightweight material, AA2024.
Abstract
Purpose
This paper aims to evaluate the validity of bilinear hardening model to represent the stress flow of high-pressure torsion (HPT)-strengthened lightweight material, AA2024.
Design/methodology/approach
Finite-element HPT simulation was performed by applying a simultaneous prescribed displacement on the axial and rotational axis that is equivalent to 4 GPa pressure and 30° torsion. The material behaviour incorporates plasticity attributes with a bilinear constitutive equation that consists of elastic and tangent modulus.
Findings
As a result, the von Mises stress generated from the simulation is in good agreement with the experiment, indicating that the assumptions of plasticity properties applied for the FEM simulation model are acceptable. The model verification confirms the anticipated plasticity parameters’ effect on the generated von Mises stress. The disc centre also evidenced an insignificant stress increment due to the limited shear straining.
Research limitations/implications
A reliable hardening model would assist in understanding the stress flow associated with mechanical properties enhancement.
Practical implications
The bilinear hardening model exhibits a satisfactory stress estimation. It simplifies the ideal strain variable hardening procedures and lessens the total computation time that is valuable in solving severe plastic deformation problems.
Originality/value
An integration of well-defined input parameters, concerning the hardening behaviour and the plasticity properties, contributes to the establishment of a validated HPT simulation model, particularly for AA2024. This study also proved that perfectly plastic behaviour is inappropriate to represent hardening in the HPT-strengthened materials due to the remarkable stress deviation from the experimental data.
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Fauziana Lamin, Ahmad Kamal Ariffin Ahmad Kamal Ariffin and Intan Fadhlina Mohamed
The purpose of this paper is to examine the plasticity behaviour of aluminium alloys in high-pressure torsion (HPT) compressive loading stage. It is a part of the strengthen…
Abstract
Purpose
The purpose of this paper is to examine the plasticity behaviour of aluminium alloys in high-pressure torsion (HPT) compressive loading stage. It is a part of the strengthen lightweight material development through severe plastic deformation.
Design/methodology/approach
A finite element simulation of HPT compression stage by displacement control incremental loading was proposed by taking into account an unconstraint HPT configuration. The quasi-static condition was utilised, by embedding strain hardening plasticity constitutive model and considering frictional effects, to assess the plasticity behaviour of aluminium alloys, particularly AA2024 and AA6082.
Findings
The present investigation clearly indicates that the deviation of material flow as a result of sticking condition of µ⩾0.5, was found to be negligible. An inhomogeneous material flow along the sample radial and thickness direction was evident, producing a stress concentration at the edge of the loaded surface, indicating the anticipated region of failure. The effective plastic strain in the compression stage was also found to be significant. Based on the effective strain response, plasticity behaviour of the compressed sample was predicted.
Originality/value
This paper demonstrates the plasticity behaviour of the analysed aluminium alloys. Since the mechanical properties produced by the deformed material are closely related to the exerted plastic deformation, understanding the phenomenon associated with the plastic strain development is essential. The outcome of this research will assist in seizing the opportunities of improving both material properties and the HPT procedures.
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Zn has been attracting increasing attention with its biological compatibility property as a degradable implant material. Besides mechanical properties, especially for bone implant…
Abstract
Purpose
Zn has been attracting increasing attention with its biological compatibility property as a degradable implant material. Besides mechanical properties, especially for bone implant applications, wear resistance is a crucial mechanical property. The purpose of this study is to investigate HPTed Zn samples’ tribological behavior under dry and simulated body fluid (SBF) lubrication conditions.
Design/methodology/approach
Pure Zn powders were consolidated via the high-pressure torsion (HPT) method with 1, 5 and 10 rotations. Cast pure Zn samples were used as the control group. The wear behavior of pure Zn samples was investigated under dry and SBF lubrication conditions with a ball-on testing method. The wear tracks were observed with a mechanical profilometer and scanning electron microscope (SEM).
Findings
The application of HPT not only improved the mechanical strength and degradation performance but also improved wear resistance. However, tests with SBF resulted in higher wear rates. Besides, SBF significantly masked the positive effect of HPT on the coefficient of friction (COF). Although with SBF tests, 10 HPT rotation samples resulted in the lowest wear width and volume.
Originality/value
The main originality of this study is to reveal the HPT process and SBF effects on the tribological behavior of pure Zn to observe their potential usage for bone implant applications.
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Jun Zhu, Wei Luo, Wentao Xv, Shuigen Xv, XinYang Zhang and Jiefang Zhao
This paper aims to study the electrochemical corrosion performance of ultrafine-grained (UFG) Cu bulk in 0.5 M NaCl solution.
Abstract
Purpose
This paper aims to study the electrochemical corrosion performance of ultrafine-grained (UFG) Cu bulk in 0.5 M NaCl solution.
Design/methodology/approach
UFG Cu bulk were prepared by impacting at −196°C and following heat treatment. The electrochemical corrosion behaviors of coarse-grained (CG), impacted and subsequently annealed at 190°C Cu bulks were studied.
Findings
All the bulks displayed typical active-passive-transpassive behaviors (dual passive films without stable passive regions). The resistance to corrosion of impacted Cu bulk was notably superior to that of CG Cu bulk, and subsequently annealing further improved its corrosion resistance.
Social implications
Except for mechanical properties, corrosion performance has been considered to be one of the most important aspects in bulk UFG metallic materials research for the prospective engineering applications.
Originality/value
Cryogenic impacting could effectively reduce grain size of CG Cu bulk to UFG scale and induce high density dislocation. Subsequent annealing resulted in a further decrease of grain size even to nanoscale, as well as nanometer twins. The grain refinement, high density dislocation and annealing twins effectively enhance the passivation capability, resulting in an increase in the corrosion resistance.
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Vitus Mwinteribo Tabie, Chong Li, Wang Saifu, Jianwei Li and Xiaojing Xu
This paper aims to present a broad review of near-a titanium alloys for high-temperature applications.
Abstract
Purpose
This paper aims to present a broad review of near-a titanium alloys for high-temperature applications.
Design/methodology/approach
Following a brief introduction of titanium (Ti) alloys, this paper considers the near-α group of Ti alloys, which are the most popular high-temperature Ti alloys developed for a high-temperature application, particularly in compressor disc and blades in aero-engines. The paper is relied on literature within the past decade to discuss phase stability and microstructural effect of alloying elements, plastic deformation and reinforcements used in the development of these alloys.
Findings
The near-a Ti alloys show high potential for high-temperature applications, and many researchers have explored the incorporation of TiC, TiB SiC, Y2O3, La2O3 and Al2O3 reinforcements for improved mechanical properties. Rolling, extrusion, forging and some severe plastic deformation (SPD) techniques, as well as heat treatment methods, have also been explored extensively. There is, however, a paucity of information on SiC, Y2O3 and carbon nanotube reinforcements and their combinations for improved mechanical properties. Information on some SPD techniques such as cyclic extrusion compression, multiaxial compression/forging and repeated corrugation and straightening for this class of alloys is also limited.
Originality/value
This paper provides a topical, technical insight into developments in near-a Ti alloys using literature from within the past decade. It also outlines the future developments of this class of Ti alloys.
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Severe plastic deformation (SPD) has provided new opportunities in investigations of enhanced mechanical properties like high strength and ductility by permitting grain refinement…
Abstract
Purpose
Severe plastic deformation (SPD) has provided new opportunities in investigations of enhanced mechanical properties like high strength and ductility by permitting grain refinement to a nanometer level, especially ultra‐fine grained and nanocrystalline metals and alloys. These materials have been attracting more and more research interest during the past few decades due to scientific curiosity and their engineering potentials with a significant advancement in their understanding. The purpose of this paper is to find the relationship between processing, structures and properties of these novel materials with the ultimate goal of producing a model to account for the grain size changes at the nano‐scale.
Design/methodology/approach
In this paper, specimens with various grain sizes from 23 to 80 μm are obtained via processing by SPD, using equal channel angular press (ECAP) technique. The effect of grain size on the hardness properties of nanostructured copper alloy has been investigated using micro‐hardness testing of the samples to test the mechanical properties of this material.
Findings
The results reveal that the copper alloys processed by SPD using ECAP technique after various passes differ in the grain size and mechanical properties. The hardness test exhibits grained size dependence according to Hall‐Petch relationship from room temperature. The increase in the hardness with number of passages suggest increasing in strain during deformation, as the passes increase the smaller grain size can be produced.
Originality/value
The paper usefully shows how nanostructured materials by SPD technique will offer a possible solution to the problem of using light metals for certain applications by increasing the strength of materials which could be used in structures where previously strength requirement in various industries, including such as, for example, transportation, medical devices and electronics. Understanding the relationship between processing, structures and properties will enhance the performance of metals and alloys in a target application which is important in improving the mechanical properties of engineering materials that are necessary fundamental for applications of lightweight materials and structures. The influences of structural parameters, such as grain size, grain shape on plastic deformation which is important parameters in study the mechanical properties of nanostructured materials.
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Chunhua Wei, Chenglin Niu, Youyuan Tan and Zhixin Lei
This study aims to evaluate the dry-sliding tribological properties of fine-grained tin–bronze alloy under reciprocating sliding conditions.
Abstract
Purpose
This study aims to evaluate the dry-sliding tribological properties of fine-grained tin–bronze alloy under reciprocating sliding conditions.
Design/methodology/approach
A fine-grained tin–bronze alloy was processed by multiaxial forging (MAF) and annealing treatment. Friction and wear experiments were conducted on a reciprocating sliding tribometer. Microstructure, tensile mechanical properties, hardness, wear rate, friction coefficient and wear morphologies of coarse-grained sample, MAF sample and MAF and annealing sample were compared.
Findings
After MAF, the strength and hardness increased distinctly, but the elongation decreased. The wear rate is increased, though friction coefficient is lower. Weaker work hardening leads up to higher sliding wear rate. After MAF and annealing, the alloy has higher strength, hardness and elongation. Lower wear rate of the alloy is correlated with the higher hardness, elongation and work hardening. The adhesion wear and abrasive wear are the primary wear mechanism.
Originality/value
It was found that the fine-grained alloy shows lower sliding wear rate only by combining severe plastic deformation with heat treatment. The process of MAF and annealing is useful in improving the wear resistance of tin–bronze alloy.
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Huan Wang, Yongchang Liu, Huixia Gao and Zhiming Gao
This paper aims to investigate the transformations during aging at 200°C for different periods on microstructure and mechanical properties of high-temperature Zn-4Al-3Mg solders…
Abstract
Purpose
This paper aims to investigate the transformations during aging at 200°C for different periods on microstructure and mechanical properties of high-temperature Zn-4Al-3Mg solders.
Design/methodology/approach
The solder was melted in a resistance furnace, and different cooling rates were obtained by changing the cooling medium. Subsequently, all the specimens were aged at 200°C for 20 h and 50 h. A scanning electron microscope equipped with an energy dispersive X-ray detector and X-ray diffraction were used for the observation of microstructures and the determination of phase composition. Tensile tests and Rockwell hardness tests were also performed.
Findings
After aging, Zn atoms precipitated from the supersaturated α-Al and the (α-Al + η-Zn)eutectoid phase with the original fine lamellar structure coarsened and spheroidized to minimize the system energy. Among these solders, the furnace-cooled alloys exhibited the highest thermal stability, largely retaining their original morphology after aging, whereas the collapse and spheroidization of the η-Zn phase and the coarsening of the η-Zn dendrites took place in the air-cooled and water-cooled samples, respectively. Furthermore, a decrease in tensile strength during aging was attributed to the thermal softening effect. The variation of macro-hardness was mainly associated with the microstructural alterations in terms of quantity, morphology and distribution of soft η-Zn phase and hard intermetallic compounds induced by the aging treatment.
Originality/value
The structural stability of eutectic Zn-4Al-3Mg solders solidified at different cooling rates and the effect of aging on mechanical properties were investigated.
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Rajat Yadav, Shashi Prakash Dwivedi, Vijay Kumar Dwivedi and Anas Islam
This study aims to attempt to make an aluminum-based composite using reinforcement such as graphite and fly ash. Pollution is an enhanced serious issue of concern for global…
Abstract
Purpose
This study aims to attempt to make an aluminum-based composite using reinforcement such as graphite and fly ash. Pollution is an enhanced serious issue of concern for global. Industries play a major role in disturbing the balance of the environment system. Composite is made by using the stir casting technique. The waste that is generated by the industries if left untreated or left to be rotten at some place may prove fatal to invite various types of diseases. Proper treatment of these wastes is the need of the hour, the best way to get rid of such kinds of hazardous wastes is to use them by recycling.
Design/methodology/approach
Stir casting technique was used to make a composite. Graphite and fly ash were mixed with equal amounts of 2.5% to 15% in aluminum. The microstructure of composite formed after composite was noticed. After seeing the microstructure it was understood that reinforcement particles are very well-mixed in aluminum.
Findings
When graphite was mixed with 3.75% and 3.75% fly ash in aluminum, the strength of the composite came to about 171.12 MPa. As a result, the strength of the composite increased by about 16.10% with respect to the base material. In the same way, when 3.75% graphite and 3.75% fly ash were added to aluminum, the hardness of the composite increased by about 26.60%.
Originality/value
In this work, graphite and fly ash have been used to develop green metal matrix composite to support the green revolution as promoted/suggested by United Nations, thus reducing the environmental pollution. The addition of graphite and fly ash to aluminum reduced toughness. The thermal expansion of the composite has also been observed to know whether the composite made is worth using in higher temperatures.
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Murat Isik, Isa Emami Tabrizi, Raja Muhammad Awais Khan, Mehmet Yildiz, Eda Aydogan and Bahattin Koc
In recent years, additive manufacturing (AM) has started to be used for manufacturing real functional parts and assemblies for critical applications in aerospace, automotive, and…
Abstract
Purpose
In recent years, additive manufacturing (AM) has started to be used for manufacturing real functional parts and assemblies for critical applications in aerospace, automotive, and machinery industries. Most complex or assembled parts require internal features (IF) such as holes, channels, slots, or guides for locational and mating requirements. Therefore, it is critical to understand and compare the structural and mechanical properties of additively manufactured and conventionally machined IFs.
Design/methodology/approach
In this study, mechanical and microstructural properties of Inconel 718 (Inc718) alloy internal features, manufactured either as-built with AM or machining of additively manufactured (AMed) part thereafter were investigated.
Findings
The results showed that the average ultimate tensile strength (UTS) of additively manufactured center internal feature (AM-IF) is almost analogous to the machined internal feature (M-IF). However, the yield strength of M-IF is greater than that of AM-IF due the greater surface roughness of the internal feature in AM-IF, which is deemed to surpass the effect of microstructure on the mechanical performance. The results of digital image correlation (DIC) analysis suggest that AM-IF and M-IF conditions have similar strain values under the same stress levels but the specimens with as built IF have a more locally ductile region around their IF, which is confirmed by hardness test results. But this does not change global elongation behavior. The microstructural evolution starting from as-built (AB) and heat-treated (HT) samples to specimens with IF are examined. The microstructure of HT specimens has bimodal grain structure with d phase while the AB specimens display a very fine dendritic microstructure with the presence of carbides. Although they both have close values, machined specimens have a higher frequency of finer grains based on SEM images.
Originality/value
It was shown that the concurrent creation of the IF during AM can provide a final part with a preserved ultimate tensile strength and elongation but a decreased yield strength. The variation in UTS of AM-IF increases due to the surface roughness near the internal feature as compared to smooth internal surfaces in M-IF. Hence, the outcomes of this study are believed to be valuable for the industry in terms of determining the appropriate production strategy of parts with IF using AM and postprocessing processes.
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