Powder Metallurgical Techniques Research Articles

Influence of machining process of MoS2/B4C/Az31 Mg alloy composite and its tribological characteristics

The automotive, biomedical, and aerospace industries are among those with a rising need for lightweight materials with enhanced mechanical and tribological qualities. Composites based on magnesium alloys have attracted interest because of their excellent strength-to-weight ratio and promise to improve component performance. Magnesium (Mg) alloy-based composites find applications in sports and leisure equipment, aerospace, biomedical implants, and more. The research outlined here serves a critical need in the field of materials science and engineering, particularly regarding the development of advanced magnesium (Mg) alloy-based composites. In this study, we have created a new aluminum composite using the AZ31 alloy mixed with 5% boron carbide (B4C) and 5% molybdenum disulfide (MoS2) as reinforcement through a powder metallurgical technique. The magnesium alloy contains 3% aluminum and 1% zinc. Our research aims to understand the mechanical and tribological behaviors and the impact of Electrical Discharge Machining (EDM) process parameters on AZ31 magnesium alloy. We need to modify these properties for various applications. Many industrial researchers have studied the machinability of magnesium alloys using EDM. We conducted wear tests on AZ31 alloy reinforced with both B4C and MoS2 in altered quantities using a pin-on-disc setup. The outcome displays that the wear resistance of these composites is considerably better matched to other magnesium matrix composites (MMCs). We also measured various densities of the hybrid composite, including apparent density, green density, and sintered density, which were found to be 0.839, 1.495, and 1.504 g/cm3, respectively—better than other composites. In addition, the hybrid composite exhibited a substantial increase in micro hardness, reaching 22.012 HV, indicating improved wear resistance of the material. Comparatively, low density, minimum wear profile, and maximum hardness were recorded for the sample of AZ31 + 5%MoS2 + 5%B4C. The influence of EDM parameters was discussed.

Nanomechanical analysis of friction welded similar PEEK/aluminum nanocomposites: Effect of metal particle reinforcement

AbstractAluminum (Al), poly(etheretherketone) (PEEK) thermoplastics, and their individual composites have widely been used in many industries, including aerospace and biomedical fields. However, the joining process of those composites has not been explored much to date. In this context, the friction welding process (FWP) could be used as an alternative since it has the ability to join high‐strength components with minimal distortion. Therefore, the present study aimed to develop PEEK/Al nanocomposites with varying Al concentrations of 10, 20, 30, and 40 vol% using powder metallurgical technique and further joined the similar composition composites by FWP. Then, the effect of reinforced particle concentrations on the physical, morphological, structural, thermal, and micromechanical behaviors of the joined nanocomposites has been characterized by microscopy, X‐ray diffraction, differential scanning calorimetry, and nanoindentation tests. The concentrations of the reinforcement were found to have a significant effect on the crystallinity, melting temperature, glass transition temperature, and thereby micromechanical properties. The results were analyzed and correlated precisely for all the welded nanocomposites systematically. The interdiffusion mechanism was found to be involved in improving the mechanical properties of the present nanocomposites. The highest elastic modulus (13.91 GPa) or nanohardness (0.31 GPa) was obtained for the rotatory part of the PEEK/Al40 nanocomposites at 80 mN load. But, the applied load of 40 mN was the best loading condition due to the uniform change in modulus and nanohardness of all the nanocomposites. Therefore, the present alternative joining method of the PEEK/Al nanocomposites might be used for aerospace components.Highlights Development of PEEK/aluminum with 10, 20, 30 and 40 vol% Al nanocomposites. Friction welding of similar composite material, PEEK/Al‐PEEK/Al nanocomposites. Microstructural, thermal, and nanomechanical analyses. Effect of metal particle reinforcement on the friction welded nanocomposites. FW PEEK/Al40 nanocomposite is found to be the best.

Experimental Analysis of Fatigue Crack Path for Strained Functionally Graded Materials

This paper experimentally discusses crack paths in strained Functionally graded materials under constant loading conditions and vibration fatigue. The objective is to synthesize the body of knowledge on the stability of FGM. The article presents the development, production, and characterization of multi-Al (aluminum), Ni (nickel), and Titanium alloys. FGM it was successfully modified using the powder metallurgical technique. Five-layer FGM samples frequently utilize (Al, Ni), on one end and (Al-Ni-Ti) on the first. FGM sample mechanical characteristics have been investigated using wear and Fatigue testing. The Al/Ni/Titanium FGM compact specimen approaches the yield stress and ultimate stress values, which is regarded as a significant improvement in mechanical qualities with less weight. The test findings are for a constant amplitude load fully reversed with zero mean stress. The stress life approach examined three samples' fatigue characteristics and natural frequency under random vibration.

Microstructure, mechanical and thermal properties of titanium matrix composites with different reinforcements

In this study, three titanium matrix composites (TMCs) reinforced with graphite, graphene, and boron carbide (B4C) were fabricated through powder metallurgical techniques. The morphologies of grains and secondary phases of these TMCs were observed through Optical Micrograph (OM) and Scanning Electron Microscopy (SEM). The results of the mechanical properties of the TMCs showed that B4C was the most effective in increasing the strength and hardness, while the strengthening effect was comparable between graphite and graphene. The plasticity of the graphene reinforced TMC decreased sharply because of the formation of strip-like agglomerations. The small size, large volume fraction, and uniform distribution of the secondary phases contributed to the enhancement of strength and hardness in boron carbide reinforced TMC. Although the thermal properties of the TMCs were lower than pure titanium in the temperature range of 25 ∼ 300 °C, the thermal conductivities of the TMCs were all above 15.6W m−1·K.

Validation of Archimedes Method and Acid Dissolution Test for Volume Fraction Determination of Aluminum Alloy Composites Reinforced with Ceramic Particles

Metal matrix composites are the novel engineering materials finding applications in several extreme environmental and industrial requirements leading to the developments of numerous types of its kind in recent decades. Powder metallurgical techniques is one among the promising methods of producing intricate shaped end products out of the MMCs. Essentially the uniformity in distribution of the reinforcements and the accuracy in employing the percentile addition of the reinforcements decide the tailor made properties of these composites. There are several techniques to evaluate the reinforcement percentage and uniformity. This work concentrates on the analysis of effectiveness of volume fraction determination methods namely Archimedes test and acid dissolution test for 7075 Al/Al2O3 composite. Using the two methods the volume fraction of 7075Al/ Al2O3 composite prepared by powder metallurgy technique is determined. Advantages and disadvantages of both methods were analyzed using the result analysis and the observation indicated that the acid dissolution test produces more accurate results than the Archimedes test. In addition, the randomized selection of the specimens out of the end products leads to the corroboration of reinforcement uniformity in the composite matrix.

Effect of powder variability on laser powder bed fusion processing and properties of 316L

To date, the effects of powder properties, both physical and chemical, on the printed properties of as-built components is still a topic that is poorly understood. A contributing factor is the lack of relevant methods for evaluating the rheological properties of powder, or flowability. This study presents a review of different 316 L powder grades that were produced using various atomization techniques. The physical powder properties were evaluated using powder metallurgical techniques, a powder rheometer (FT4) and a rotating drum analyser (RPA). The results indicate that both the FT4 and RPA are suitable for powder characterization. However, the parameter selection for evaluation must be done keeping in mind the application, in this case thin layer powder spreading. It was found that all bulk powder density measurements, basic flow energy and the break energy were able to both differentiate between powder grades and predict how suitable the powder will be for the laser-based powder-bed fusion process. Despite some printability challenges of the water atomized grades at higher layer thicknesses, it was found that both gas atomized grades performed similarly despite minor differences in particle size distribution. Furthermore, powder variability did not show any detrimental effects on the resulting mechanical properties.

Enhancing the thermoelectric properties of powder metallurgically produced BiSbTe alloy through feasible electroless surface coating method

The powder metallurgical techniques capable of powder mass production but lacks in achieving high zT. Therefore, to improve zT, electroless surface coating was performed on water atomized Bi0.5Sb1.5Te3 (BST) powder and stimulated their conducting nature. Surface chemical composition studies displays fine elemental coating on the BST powders and remarkably, the Seebeck coefficient increased till 450 K. The surface coated bulk sample shows greatly improved power factor about ~45% higher than uncoated sample. Indeed, at high temperature we obtained reduced lattice thermal conductivity which confirms the remarkable suppression of bipolar thermal conductivity. Consequently, a maximum zT of 1.16 at 400 K achieved by coated samples which is ~102% enhancement compared to original BST. Also, we attained high average zT of ~0.99 which helps in employing thermoelectric devices across wide temperature. Therefore, electroless surface coating could be a feasible method for improving the properties of mass-produced BST powder.

Synthesizing Aluminum Matrix Composites by Combining a Powder Metallurgical Technique and an <i>In Situ</i> Method

A method of synthesizing dispersion-strengthened aluminum matrix composites using a powder metallurgical technique and an in situ method was considered. Methods combination was aimed at ensuring energy efficiency, avoiding vacuum treatment of the reaction medium, and using inert gasses to protect from oxidation. Reinforcement phase precursors are capable of ensuring good wettability of dispersed particles by the molten matrix metal. The options of the methods’ practical implementation are presented by the example of producing aluminum matrix composites filled with various functional particles.

Experimental Investigation on Surface Roughness and Metal Removal Rate of Aluminium 2024 Alloy

Abstract: The purpose of this work is to investigate experimentally the surface roughness and MRR while machining of aluminium 2024 alloy which is prepared by powder metallurgical technique. Aluminium 2024 alloy prepared with different composition such as Pure Al, 1.5 W% of Mg and 2-6 % of Cu powders. Powders are blended with ball milling machine according to the composition required and specimens are prepared in square shape die (25*25mm) by applying uniaxial load of 200Mpa. The sintering process was performed at 594 0C for 60 min and cooled at room temperature. SEM and XRD analysis was carried out to know various characteristics like green density, dimensional changes during sintering, sintering density, mechanical properties and microstructures. Finally the Surface roughness and MRR during machining with CNC milling machine at different depth of cuts was also evaluated. Keywords: Aluminium 2024 alloy, surface roughness, MRR, SEM and XRD analysis

Mechanical behavior of shape memory alloy fiber reinforced aluminum matrix composites

This study aims to investigate mechanical behavior of NiTi shape memory alloy (SMA) long-fiber reinforced aluminum (Al) matrix composites, experimentally and numerically. The composites with three different pre-memorized shapes of SMA fibers, which were straight-, wave- and rectangle-shaped fibers, were fabricated by powder metallurgical techniques. Three-point bending and tensile test results demonstrated that wave-shape SMA/Al composites showed the highest elastic modulus and strength, and wave-shape and rectangle-shape SMA/Al composites showed high Poisson’s ratio (lateral to longitudinal strain ratio in elastic-plastic regime). The experimental results were examined based on finite element analysis (FEA). It was concluded that internal stresses in the composites, which were introduced during the fabrication processes, highly affected their subsequent mechanical behavior of the composites.

Development of Ti–Zr alloys by powder metallurgy for biomedical applications

ABSTRACT Commercial pure titanium offers excellent biocompatibility, but its properties are poor for some biomedical applications where both mechanical properties and biocompatibility are required. The study attempts to evaluate the developement ofTi–Zr alloys using conventional powder metallurgical techniques by mixing elemental powder (BE) or mechanical mixing (MA) as a function of the zirconium content (6, 15 and 20 wt-%). Sintering was performed at 1523 K after compaction at 700 MPa for BE powders and 900 MPa for MA powders. Sintered parts were tested to obtain maximum flexural strength. Samples were characterised microstructurally by X-ray diffraction to study the phases. Optical microscopy (OM) and scanning electron microscopy (SEM) were performed to study the phases, porosity, grain size. Flexural strength to Ti CP was greater, but slightly diminished with increasing Zr content. However, the elastic modulus increased slightly compared to Ti. The results obtained show that it is possible to make these alloys by powder metallurgy.

Spark Plasma Sintering of Titanium Aluminides: A Progress Review on Processing, Structure-Property Relations, Alloy Development and Challenges

Titanium aluminides (TiAl) have the potential of substituting nickel-based superalloys (NBSAs) in the aerospace industries owing to their lightweight, good mechanical and oxidation properties. Functional simplicity, control of sintering parameters, exceptional sintering speeds, high reproducibility, consistency and safety are the main benefits of spark plasma sintering (SPS) over conventional methods. Though TiAl exhibit excellent high temperature properties, SPS has been employed to improve on the poor ductility at room temperature. Powder metallurgical processing techniques used to promote the formation of refined, homogeneous and contaminant-free structures, favouring improvements in ductility and other properties are discussed. This article further reviews published work on phase constituents, microstructures, alloy developments and mechanical properties of TiAl alloys produced by SPS. Finally, an overview of challenges in as far as the implementation of TiAl in industries of interest are highlighted.

Effect of Molybdenum Addition on Microstructural and Mechanical Characterization of Highly Porous Steels

In this work, the influences of adding different amounts of molybdenum (0, 0.5, 1, 2, and 4 wt%) on the microstructure and mechanical properties of highly porous steels fabricated using powder metallurgical water-leachable space holder technique were studied. The microstructure of cell walls and morphologies of cells and micro-pores were evaluated using an optical microscope and scanning electron microscope equipped with X-ray energy dispersive spectroscopy. To evaluate the mechanical properties, compression tests were conducted on the highly porous steel specimens. The results demonstrated that about 90 wt% of urea granules are discontinuously removed during the multi-stage leaching process. The relative density of the highly porous steels was measured between the range of 0.18 and 0.22 and it increased by adding the molybdenum content. Ferrite, fine pearlite, and distributed molybdenum islands formed the microstructure of cell walls. The stress–strain curves contained linear elastic region, long saw-toothed plateau region, and fracture point. By changing the amounts of molybdenum from 0 to 4 wt%, mean modulus of elasticity, plateau stress, and density of energy absorption showed 0.75, 7.32, and 6.75 times improvement, respectively. Also, yield strength and failure strain revealed up–down behavior.

Carbon nanotube reinforced aluminium composites fabricated by powder metallurgical and hot-rolling techniques

This research aims to fabricate light weight and high strength materials such as multi-walled carbon nanotubes (CNT) reinforced aluminium composites at relatively low cost. CNT/Al composites have been fabricated in three steps: (1) preparation of CNT dispersion, (2) preparation of CNT/Al based composite material by powder metallurgical slurry method, and (3) strengthening and refining of CNT/Al based composites by rolling processes. After fabrication, the composites have been characterized on dispersibility of CNT, Vickers hardness, three-point bending and tensile properties.

Experimental investigations of reciprocating wear behavior of metal matrix (Ti/TiB) composites

In this paper, the reciprocating wear behavior of titanium–titanium boride composites with 20 and 40 (by vol. %) titanium boride (TiB) particles IS investigated in dry sliding conditions against Al2O3 ceramic balls. The trials have been observed at three loading conditions such as 5, 10 and 15 N load. The composites were processed by three powder metallurgical techniques such as spark plasma sintering (SPS), vacuum sintering (VS) and hot isostatic pressing (HIP). The electron probe microanalysis (EPMA) was used to analyze the homogeneity of Ti and boride phases in the composites. The hardness and indentation fracture resistance were evaluated using nano-indentation technique. The load–depth curves of indents for Ti–TiB shows the deviations of the modulus of elasticity within the spark plasma sintering (SPS), vacuum sintering (VS) and hot isostatic pressing (HIP).The wear resistance of the fabricated samples was analyzed using reciprocating wear tester. The SPS composite (Ti–38.5% TiB) showed lower coefficient of friction (0.07), lower wear volume (0.4368 mm3) and wear rate (0.000276 mm3/m) when compared to HIP and VS, which is attributed to the presence of fine titanium boride needles of high hardness, contributing to improving wear resistance. The surface morphology reveals that the composites processed through spark plasma sintering (SPS) and hot isostatic pressing (HIP) are subjected to minor plastic deformation. The outcome of this work is more beneficial to automotive brake pad, precision manufacturing and locomotives to avoid critical wear failures.

The effect of multi-scale Cu distribution regulation on magnetic properties of Sm(CoFeCuZr)z magnets

Correlation between Cu distribution and magnetic properties was studied for Sm(CobalFe0.28Cu0.07Zr0.02)7.6 magnets prepared by conventional powder metallurgical techniques. It reveals that the micrometer scale Cu distribution homogeneity before aging treatment has a profound influence on the cell structure, nanometer scale Cu distribution, which determines the magnetization and demagnetization behavior as well as magnetic properties of the magnets. By tuning the solution treatment conditions, magnet with optimal magnetic properties (remanence of 11.5 kG, coercivity of 23.4 kOe, and maximum energy product of 30.3 MGOe) was prepared.

Experimental investigation of mechanical and tribological properties of Aluminium metal matrix composites fabricated by powder metallurgy route – A review

Additive manufacturing is being viewed as the future of manufacturing and is one of the most actively explored cutting edge research area in manufacturing. Powder metallurgical technique has the unique advantage of near net shape manufacturing, getting rid of finish machining processes and hence material wastage. Mechanical alloying is the solid state alloying technique that combines constituent metal powders, via powder metallurgical route, ending up with alloys that are quite comparable to traditionally manufactured alloys. Metal powders are blended with a help of ball mill to achieve a standardised distribution, prior to compaction. Hybrid metal matrix composites exhibit two different secondary phases distributed in the primary phase, exhibit interesting behaviour and are worthy to be explored in the area of composite research. This review delineates various such literatures about mechanical alloying of aluminium with different constituent alloying metals and compounds and the outcomes of such works, in comparison to traditionally fabricated alloys.

Study on formability and strain hardening index: influence of particle size of boron carbide (B4C) in magnesium matrix composites fabricated by powder metallurgy technique

In the present investigation, Magnesium composites have been fabricated with boron carbide (B4C) as reinforcement by powder metallurgicaltechnique. Two different particle sizes—micro and nano B4C particles with weight percentage of 0%, 5% and 10% has been studied. The green compacts were prepared by cold pressing and then sintering the specimens before being subjected to cold upsetting under triaxial stress state condition in order to study the phenomenon of workability and instantaneous strain hardening index. Powder characterizations are discussed using x-ray Diffraction peaks, Scanning Electron Microscope images and Energy Dispersive Spectrum analysis. Cold upsetting has been preferred to investigate the performance of the composites. The values of formability stress index factor (βσ), various stress ratio (σθ/σeff, σm/σeffandσz/σm) parameters and instantaneous strain hardening index (ni) are observed for increase in % of B4C particles and its sizes. The experimental results were analyzed pertaining to relative density. The results reveal that Mg-10% nano B4C composite has higher relative density, formability stress index factor and hence high workability than the other composites. The addition of B4C particles as reinforcement affects the strain hardening index due to geometric and work hardening of the composites.

Growth and Properties of TiN/Al2O3/Ti(C, N)/TiN Multilayer CVD Coatings on Ti (C, N)-Based Cermet Substrates with Ni, Co and Fe Binders

In this article, Ti (C, N)-based cermets with Ni, Co and Fe binder phase were manufactured by traditional powder metallurgical techniques. The multilayer TiN/Al2O3/Ti (C, N)/TiN CVD (chemical vapor deposition) coatings were deposited on the three kind of cermets, and the growth and properties of the coatings were studied. The results show that massive cores-incomplete rims are found in the cermet-Ni (cermets with Ni binder) and cermet-Fe (cermets with Fe binder), while in the cermet-Co (cermets with Co binder), the small black cores are surrounded by a complete and well-developed rim phase. When the TiN coating is deposited on the cermets with cores-incomplete rims, the Ti and N atoms stack on the face-centered cubic structure of Ti (C, N) first, and epitaxial growth of the TiN crystals takes place. The epitaxial growth is attributed to the same preferred orientation (2 0 0) of the TiN layers to the Ti (C, N) of the substrate. While on the cermets with cores-complete rims, (Mo, Ti) (C, N) solid solution and binder phase (Ni/Co/Fe), which has a distinct crystal structure or lattice parameters, TiN grains nucleate first and then grow. In this case, the TiN coatings show a (1 1 1)-oriented structure. Dense and thin coatings grow on the cermets-Co. The adhesion of the multilayer coatings to the substrate increases in the order cermets-Fe, cermets-Ni and cermets-Co. In addition, the coating on the cermets-Co has the lowest COF (coefficient of friction) as the thin TiN layer (0.7 μm) is propitious to diffusion of Al and O, and a protective transfer layer is formed by AlOx.

Influence of the Compaction Pressure and Sintering Temperature on the Mechanical Properties of Porous Titanium for Biomedical Applications

In the present work, the use of porous titanium is proposed as a solution to the difference in stiffness between the implant and bone tissue, avoiding the bone resorption. Conventional powder metallurgical technique is an industrially established route for fabrication of this type of material. The results are discussed in terms of the influence of compaction pressure and sintering temperature on the porosity (volumetric fraction, size, and morphology) and the quality of the sintering necks. A very good agreement between the predicted values obtained using a simple 2D finite element model, the experimental uniaxial compression behavior, and the analytical model proposed by Nielsen, has been found for both the Young’s modulus and the yield strength. The porous samples obtained by the loose sintering technique and using temperatures between 1000 °C −1100 °C (about 40% of total porosity) are recommended for achieving a suitable biomechanical behavior for cortical bone partial replacement.