Powder Metallurgical Route Research Articles

Fabrication of bulk-sized W-1.1%TiC alloy with helium bubble retention via powder metallurgical route incorporated with helium ambient mechanical alloying

In the field of materials irradiation, it has been noted that incorporating helium (He) element into metals may have the beneficial effect of improving both strength and ductility in the high temperature region where creep occurs. In order to fabricate such new functional materials and apply them to a wide range of fields, it is necessary to establish new fabrication methods for bulk-size materials. In this study, bulk-sized W-1.1%TiC alloys containing He bubbles were fabricated by a powder metallurgical route using mechanical alloying in a He atmosphere and subsequent thermo-mechanical processing. Transmission electron microscopy observations showed that this fabrication process successfully incorporated nano-sized He bubbles into W-1.1%TiC. Since this fabrication process is free of radioactivation and irradiation-induced defects, it will facilitate research into the fundamental understanding of the independent effects of He bubbles on the physical and mechanical properties of various materials concerned.

Poly(ether-sulfone)/MWCNT nanocomposites manufactured by powder metallurgy route and their dynamic mechanical properties

Dynamic mechanical properties of the poly(ether-sulfone) (PES)/multi-walled carbon nanotube (MWCNT) nanocomposites manufactured by powder metallurgical route was discussed for the first time. The structural investigation of the nanocomposites was analysed by x-ray diffraction. At room temperature, both storage modulus and microhardness of the nanocomposites increased by more than 60% while the strengthening efficiency at higher temperatures is several-folds compared to that of neat PES. The nanocomposites exhibited better damping behaviour compared to neat PES. The Cole–Cole plot indicated a good interaction between the PES and the MWCNT. Moreover, the coefficient of reinforcement decreased by 42% while the degree of entanglement increased.

On the properties of cast and powder metallurgical Cu–6Ni-1.5Si-0.15Al (wt.%) alloy

In this study, Cu–6Ni-1.5Si-xAl (x = 0 and 0.15 wt%) alloys are manufactured as billet materials by casting and their metallurgical and physical properties are characterized. Aluminum modified alloy is obtained also by a powder metallurgical (PM) route and its structural properties are determined to be compared with the cast materials. The findings indicate that (i) solidified alloys have distributed nickel silicides (27.01 %) embedded in α-Cu(Ni,Si) solid solution, (ii) the addition of aluminum increases the amount of silicides (29.09 %) in the solidified matrix and reduces both the grain size and the secondary dendrite arm spacing, (iii) although PM alloy has similar microstructural features as cast alloys, it exhibits the highest hardness (159 HV1) due to both finer grain structure and better distribution of silicides, (iv) both impurity and porosity have a determining effect on the electrical conductivity (27–32 % IACS, International Annealed Copper Standard) values of the alloys.

Viscoelastic behaviour of poly(ether-ketone)/fly ash composites fabricated by powder metallurgical route

Poly(ether-ketone)/fly ash (FA) composites reinforced with 0-30 wt% FA were fabricated using ball milling followed by hot compaction. The composites were investigated for mechanical and viscoelastic properties. Scanning electron microscopy revealed excellent dispersion and good adhesion of FA particles with the matrix. The addition of FA increased the microhardness by 70% and the storage modulus (below glass transition) by 75%. The reinforcing efficiency was better above the glass transition, which increased to around 177% at 250°C. This research indicates that the FA can be used as an alternative reinforcement of costly ceramic powder for the electronic packaging substrate or printed circuit board applications.

Bimodal structured chromium-tungsten composite as plasma-facing materials: Sinterability, mechanical properties, and deuterium retention assessment

Even though tungsten (W) is considered to be the most favored plasma-facing material (PFM) for nuclear fusion reactors thanks to its beneficial physical properties, its advantage for those plasma-facing components to be subjected to medium heat flux and high neutron irradiation dose is compromised by unfavorable nuclear behavior such as intermediate-level radioactive waste activation and embrittlement caused by lattice damage and transmutation. Chromium (Cr) or Cr-based materials may have the potential to mitigate these shortcomings while maintaining acceptable thermal and physical performances required for PFM. They could offer attractive design options, particularly for those parts where the particle fluxes are relatively low and the heat flux is not too high (≤ 5 MW/m²) while nuclear loads are high (≥ 5 dpa). In this article, we report the first results of a preliminary technology feasibility study for an engineered Cr-based material fabricated based on a powder-metallurgical route. To explore an optimal metallurgical condition ensuring reasonable mechanical properties and low deuterium retention, a novel two-phase Cr-W composite was developed via current-assisted rapid sintering at low sintering temperature. The composite showed a cell-like bimodal microstructure consisting of a coarse-grained Cr phase surrounded by a 3D interconnected network of an ultrafine-grained W phase. The composite exhibited substantial improvements in ductility as well as high-temperature strength compared to pure W and Cr. After undergoing W heavy ion irradiation, the damaged Cr-W composite with a two-phase bimodal microstructure showed a comparable deuterium retention capacity to pure W. Finally, the potential applicability as PFM is discussed.

Pressing and Sintering of Titanium Aluminide Powder after Ball Milling in Silane-Doped Atmosphere

Due to the high specific surface area of titanium aluminide powders, significant and unavoidable surface oxidation takes place during processing. The resulting oxides disrupt the conventional powder metallurgical process route (pressing and sintering) by reducing the green strength and sintered properties. Oxide-free particle surfaces offer the potential to significantly increase particle bond strength and enable the processing of difficult-to-press material powders. In this work, the effect of milling titanium aluminide powder in a silane-doped atmosphere on the component properties after pressing and the subsequent sintering was investigated. Ball milling was used to break up the oxide layers and create bare metal surfaces on the particles. With the help of silane-doped inert gas, the oxygen partial pressure was greatly reduced during processing. It was investigated whether oxide-free surfaces could be produced and maintained by milling in silane-doped atmospheres. Furthermore, the resulting material properties after pressing and sintering were analysed using density measurements, hardness tests, EDX measurements, and micrographs. It was concluded that ball milling in a silane-doped atmosphere produces and maintains oxide-free particle surfaces. These oxide-free surfaces and smaller particle sizes improve the component properties after pressing and sintering.

Evolution of Tungsten Fiber‐Reinforced Tungsten‐Remarks on Production and Joining

Material issues pose a significant challenge for the design of future fusion reactors. These issues require new advanced materials to be developed. W‐fiber‐reinforced W‐composite material (W f/W) incorporates extrinsic toughening mechanisms increasing the resistance against failure and thus granting steps toward application in a future fusion reactor. W f/W can be produced based on chemical vapor deposition or powder metallurgical routes. In this contribution, the efforts of upscaling the production of W f/W will be reviewed based on recent results. In addition, the activities related to enabling large‐scale production for new fusion applications are being studied. Herein, two main achievements are to be highlighted. First, an upscaled production is established to produce flat tile samples for joining tests on copper and steel, and second, a new method of joining W f/W on copper is established and tested under high heat‐flux conditions.

XRD analysis and surface roughness of AL2024 alloy produced through P/M route and machined by using CNC milling machine

The purpose of this analysis is to examine the surface roughness during machining of aluminum 2024 prepared through the powder metallurgical (P/M) route. Aluminium 2024 alloy is prepared with different compositions, such as pure Al, 1.5 W% of Mg, and 2–6% of Cu powders. Powders are blended with the ball milling machine according to the composition required, and green compacts are prepared in a square-shaped die (25*25mm) by applying a uniaxial load of 250 Mpa ±50. The sintering process was performed at a temperature of 594 °C for 60 minutes, and the heating profile consisted of a 10-minute isothermal keep at 594 °C followed by cooling in Furness. It presents and addresses compaction characteristics, green density, dimensional changes during sintering, sintering density, mechanical properties, and microstructures. Also determined were the surface roughness and MRR during machining with a CNC milling machine at different depths of cut.

MoB2/MoB ceramic particulate reinforced W-1 wt % Ni matrix composites as potential plasma facing materials

This study reports on the synthesis and characterization of MoB2/MoB ceramic particulate reinforced W-1 wt % Ni matrix (W1Ni) composites for their potential usage as plasma facing materials. A powder metallurgical route consisting of mechanical alloying (MA), cold pressing (CP), cold isostatic pressing (CIP) and pressureless sintering (PS) was applied for the production of MoB2/MoB particulate reinforced W1Ni composites. Different percentages of MoB2/MoB (x = 1, 2, 5 and 10 wt %) were incorporated into W1Ni pre-alloy. MA was performed in a planetary ball mill for different times as 24, 48 and 72 h. After compaction using CP and CIP, green bodies were pressureless sintered at 1400 °C for 1 h under Ar/H2 gas flow. According to the results of XRD characterization, and lattice strain, crystallite size and particle size analyses performed on the powders, MA time was determined as 72 h with an average lattice strain of 2.37% and crystallite size of 7.40 nm. Sintered samples characterized in terms of compositional, microstructural, wear, density and microhardness properties exhibited that W1Ni-10 wt % MoB2/MoB composite has the highest hardness value of ∼6.74 GPa and the lowest wear volume loss of 2.08 × 10-4 mm3, as compared to those of other samples. Sintered samples exposed to 20 eV He+ ion irradiation with a flux of 1.102 × 1021 ions/(m2s), irradiation fluence of 1.32 × 1024 ions/m2 for 20 min had a degraded wave-shaped structure (wavy erosion layers) on their surfaces. However, W1Ni-2 wt % MoB2/MoB composite showed relatively more resistant to ion irradiation attributed to its higher densification rate.

Rietveld refinement, 3D view and electrochemical properties of rare earth lanthanum doped nickel ferrite to fabricate high performance electrodes for supercapacitor applications

Rare earth lanthanum doped nickel ferrite with chemical formula NiLaxFe2-xO4 having composition (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) have been synthesized using powder metallurgical route for the first time. The structural, morphological and electrochemical analysis of spinel ferrites have been studied by X-ray Powder Diffractometer (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Cyclic Voltammtery (CV) and Galvanostatic Charging- Discharging (GCD) techniques. The structural analysis confirms the single–phase spinel ferrite. In order to refine the XRD data, Rietveld refinment method has been used. The Rietveld refinement specify the cubic phase of ferrite with the space group Fd3m. The surface analysis reveals the uniformally distributed spherical particles. The chemical composition of pure and La+3 doped nickel ferrites are in accordance with stoichiometric calculation. The lanthanum plays a vital role to improve the performance of electrochemical behavior for supercapactor applications. As the concentration of lanthanum increases the value of specific capacitance also increases. The highest specific capacitance is achieved at x = 0.4 which is ∼1050 F/g−1 at the low scan rate of 10 mV/s. Hence the fabricated lanthanum doped nickel ferrite electrodes may be recommended as a favorable candidate for the energy storage application like supercapacitor.

Microstructural Characterization of Novel ZrO2 Dispersion-Strengthened 9Cr Steel by Spark Plasma Sintering

Technologically important Oxide Dispersion-Strengthened steels are synthesized using ZrO2 as a dispersion strengthener instead of conventionally used Y2O3. Powder metallurgical route followed by spark plasma sintering is adopted for synthesizing the material. Detailed microstructural characterization revealed a fine-grained microstructure with finer dispersoids in as-sintered and normalized condition. The stable microstructure is found to be retained even after subjecting the samples at 973 K for as long as 1000 h for long-term thermal aging trials, indicating at a possible superiority of this material over the conventional Oxide Dispersion-Strengthened steels. The yield strength is calculated by making use of microstructural parameters and predictive models, both of which shown a good agreement. Mechanical property analysis through hardness measurements was correlated with microstructural observations and compared with the conventional Oxide Dispersion-Strengthened steels. The collective results indicate ZrO2 as a potential alternate dispersoid for strengthening steel and future scope for vast exploration.

Effect of Al2O3 and ZrO2 Filler Material on the Microstructural, Thermal and Dielectric Properties of Borosilicate Glass-Ceramics

Various glass-ceramics are widely used or considered for use as components of microelectronic materials due to their promising properties. In this study, borosilicate glass was prepared using the powder metallurgical route and then mixed with different amounts of Al2O3 and ZrO2 filler materials. Glass-ceramics are produced by high-energy ball milling and conventional sintering process under Ar or air. In this study, the effects of different filler materials and different atmospheres on the microstructural, thermal and dielectric properties were investigated. The data showed that ZrO2 filler material led to better results than Al2O3 under identical working conditions and similar composite structures. ZrO2 filler material significantly enhanced the densification process of glass-ceramics (100% relative density) and led to a thermal conductivity of 2.904 W/K.m, a dielectric constant of 3.97 (at 5 MHz) and a dielectric loss of 0.0340 (at 5 MHz) for the glass with 30 wt.% ZrO2 sample. This paper suggests that prepared borosilicate glass-ceramics have strong sinterability, high thermal conductivity, and low dielectric constants, making them promising candidates for microelectronic devices.

Fabrication, property and performance evaluation of Stainless Steel 430L as porous supports for metal supported solid oxide fuel cells

Metal-supported solid oxide fuel cells (MS-SOFCs) have attracted increasing attention due to their superior mechanical strength, relatively low material cost, and capability of fast thermal cycling, as compared to the conventional all-ceramic solid oxide fuel cell. However, fabrication of MS-SOFCs still remains challenging. This study reports a cost-effective powder metallurgical manufacturing route for producing MS-SOFCs. Stainless steel 430L (SS430L) powder is selected for producing the metal support due to its relatively low cost and good thermal expansion compatibility. MS-SOFC button cells with the SS430L/YSZ|Ni/YSZ|YSZ|LSCF structure were successfully prepared by co-sintering and ultrasonic pyrolytic spraying. We found that the trace oxygen level in the dilute H2/Ar gas mixture could play a drastic role in laboratory sintering of the SS430L support; local oxygen control is essential, particularly to avoid Cr oxidation. The addition of no more than 10% YSZ as a second phase to SS430L substantially minimized over-sintering of the SS430L support, leading to a more porous metallic-type substrate, while the electrical conductivity and thermal expansion were not much affected. The fabricated MS-SOFC button cells with the SS430L/YSZ|Ni/YSZ|YSZ|LSCF structure delivered a maximum power density of 180 mW cm-2 at 800°C with an open-circuit voltage of 1.13 V, using dry hydrogen as the fuel and ambient air as an oxidant. A cell tested at 750°C showed relatively good stability for a period of 140 h. While the performance still needs further optimization, the high OCV and good stability indicated that the reported powder metallurgy route is a promising method, and the relevant experimental details, particularly on producing metallic and oxidation-free porous supports, are critical for the preparation of MS-SOFCs.

Development of Copper - Diamond - CNT Composites via Powder Metallurgical Route for Enhanced Strength and Thermal Conductivity

Development of Copper - Diamond - CNT Composites via Powder Metallurgical Route for Enhanced Strength and Thermal Conductivity

A novel powder-metallurgical eco-friendly recycling process for tool steel grinding sludge

This work comprehensively investigates the reuse of AISI D2 tool steel grinding sludge as secondary raw material into a powder metallurgical process route. The tool steel grinding sludge initially contains about 15 mass% of silicon carbide and aluminium oxide abrasive particles as well as residual cooling lubricant emulsion consisting of water and oil leading to an increased carbon content of 2.56 mass%. A three-stage decontamination procedure of the grinding sludge is performed, including drying, removing non-metallic abrasive particles via magnetic separation, and recovering the cooling lubricant oil by supercritical carbon dioxide extraction. Subsequently, the prepared grinding metal chips are densified by a novel energy efficient short-time sintering technique called electric discharge sintering. The carbon content of the sludge could be reduced to 1.71 mass%. However, it was found that remaining contaminations lead to a change in the alloying composition of the recycled material, which influences the tempering behavior. Increased carbon and silicon levels promoted a high retained austenite fraction after quenching of more than 67 vol%. By adopting the heat treatment, the hardness of the recycled samples could be adjusted to a level similar to that of the cast reference material in quenched and tempered condition. Reducing the retained austenite content to 2.3% by tempering led to a hardness of roughly 700 HV1.However, the recycled material showed less than 40% of the compressive strength of the cast reference material. On the one hand, the lower compressive strength can be attributed to the inadequate removal of oxidic abrasive particles during the recycling process and their poor integration into the metal matrix of the compacted specimens. In addition, oxidized layers on the chip surfaces counteract metallurgical bonding between the chips during electric discharge sintering.

Synthesis of a novel Al foam with a periodic architecture by introducing hollow Al tubes and Al/Mg powders

In this work, we synthesized a brand-new Al foam with a periodic structure via a simple powder metallurgical route. The periodic architecture consists of both hierarchical porous and bi-directional composition-graded structures. The results show that the hierarchical porous material includes large pores on millimeter scale inheriting from the hollow structure of the Al tubes, and small pores on micrometer scale produced by the sintering of Al/Mg powders. The bi-directional Mg concentration-graded structure is formed in the tube walls due to the condensation of Mg vapor in the inner tube wall. The addition of Mg powders achieves excellent metallurgical bonding between the Al powders and the hollow tubes at 550°C. The plateau stress and energy absorption capacity of the Al foam in y-axis compression are significantly higher than that in the x-axis due to their anisotropic structure. In general, the Al foam with Mg addition presents the most superior compression performance, and we believe that our findings could open up a unique strategy for developing high-performance metallic foams with the periodic architecture involving both hierarchical porous and bi-directional graded structure.

Examining the surface roughness and kerf quality of micro-slots cut on the surfaces of Ti-B4C nanocomposites by WEDM: a desirability approach

Micro slots and textures are created on Titanium (Ti) composites to improve its surface characteristics. Micro-textured Ti composites are generally recommended for bio implants, automobile, and aerospace components. In the current research, Ti-B4C nanocomposites were prepared by powder metallurgical route. Micro slots were cut on the Ti-B4C surfaces by Wire Electrical Discharge Machining (WEDM) Technology by varying the current, pulse-ON time, and pulse-OFF time. Scanning electron microscopy and XRD analysis validates the uniform distribution and inclusion of B4C nanoparticles in Ti matrix. Response surface methodology was used to plan the experimental runs. Analysis of variance and desirability analysis were employed to identify the most suitable machining factors for obtaining the minimum surface roughness, lower kerf width and higher material removal rate (MRR). Increase in applied current and pulse-ON time, increases the MRR. Increase of pulse-OFF time from 50 μs to 60 μs gradually reduces the MRR and reduce the surface roughness of the cut slots. Contrastingly an increase in pulse-ON time increases the roughness due to an extensive melting and resolidification of Ti nanocomposites. The morphology of the WEDMed surface reveals the recast layer and localized melting zones on the cut surfaces.

Few-layered graphene reinforced Al-10 wt% Si-2 wt% Cu matrix composites

Few-layered graphene (FLG) reinforced Al-10 wt% Si-2 wt% Cu (Al10Si2Cu) matrix composites were fabricated via a powder metallurgical route. FLG powders were produced in an originally designed DC arc reactor via arc discharge method. Al, Si, Cu and FLG powders were subjected to high-energy ball milling at different durations to produce ternary Al alloy with homogeneously dispersed FLG, and bulk composites were fabricated via subsequent uni-axial compaction and pressureless sintering. The effects of varying FLG amounts and milling duration on the properties of the powder and bulk samples were investigated. The characterization of as-blended and mechanically alloyed (MAed) powders and their sintered forms were performed in terms of microstructural, thermal, mechanical, wear and corrosion properties. According to the results, the hardness values of the 4 h MAed Al10Si2Cu-xFLG composites were determined as 102, 154, 191 and 241 HV for x = 0, 1, 2 and 5 wt%, respectively. Despite the greater hardness value of the Al10Si2Cu-5FLG-4h composite, its compressive strength was low due to its brittle structure. The highest compressive strength was shown by the Al10Si2Cu-1FLG as 463 MPa by an approximate increase of 53% compared to that of the Al10Si2Cu matrix. Moreover, the tribology tests showed that FLG addition (up to 2 wt%) improved the wear rate of the Al10Si2Cu matrix. However, a deteriorative effect of FLG on the corrosion resistance of the composites was determined.

Studies on Tensile Fracture and Two Body Wear Behavior of Al/Si3N4–Al2O3 Nanocomposites Prepared by Powder Metallurgical Route

Studies on Tensile Fracture and Two Body Wear Behavior of Al/Si3N4–Al2O3 Nanocomposites Prepared by Powder Metallurgical Route

Fretting fatigue behaviours of SiC reinforced aluminium alloy matrix composite and its monolithic alloy

This study presents the experimental and FEA (finite element analysis) investigations on the fretting fatigue behaviours of the metal matrix composite, 2124 Al–Cu–Mg alloy reinforced with 17 vol% of 3 μm SiC particles by a powder metallurgical route and its equivalent monolithic alloy, 2024. The predicted stress concentration and orientation from the nonlinear FEA stress analyses are aligned with the experimental observation including fretting wear damage and crack initiation and propagation. Compared with its equivalent monolithic alloy, the composite in the naturally aged condition (T4) demonstrates similar subsurface degradation but the crack propagation life is much shorter. In general, the composite has shown superior fretting fatigue performance in the low cycle regime (104 to 4x105 cycles) but not in the high cycle regime (4x105 to 107 cycles). Its fretting fatigue behaviour is interpreted in terms of higher wear resistance, delayed crack initiation, superior tensile strength in the low cycle regime. The reported fretting fatigue performance of the composite suggest the different material behaviours in low and high cycle regimes should be considered when developing a fretting fatigue damage model and assessing an engineering design.