Spark Plasma Sintering Of Powders Research Articles

ТВЕРДОСТЬ И ПРОЧНОСТЬ СПЕЧЕННОГО ЭЛЕКТРОКОРУНДА ИЗ ЭЛЕКТРОЭРОЗИОННЫХ ПОРОШКОВ

The results of the study of the hardness and strength of electrocorundum produced by spark plasma sintering of powders obtained by electroerosive dispersion of electrical aluminum in distilled water are presented. The high efficiency of recycling electrical aluminum grade AD0 by processing it by electroerosive dispersion into powders and repeated application as a charge for obtaining electrocorundum by spark plasma sintering is shown.

ИССЛЕДОВАНИЕ МИКРОТВЕРДОСТИ И ИЗНОСОСТОЙКОСТИ ЖАРОПРОЧНЫХ СПЛАВОВ, ПОЛУЧЕННЫХ ИСКРОВЫМ ПЛАЗМЕННЫМ СПЕКАНИЕМ ЭЛЕКТРОЭРОЗИОННЫХ ПОРОШКОВ СПЛАВА ЖС6У

The results of the study of microhardness and wear resistance of heat-resistant alloys obtained by spark plasma sintering of powders made by electroerosive dispersion of waste of the alloy ZhS6U distilled water are presented. Carrying out the planned measures will solve the problem of recycling waste of ZhS6U alloys and their further use and, thereby, reduce the cost of production of the final product.

Optimization of manufacturing process of heat-resistant nickel alloy by spark plasma sintering of powders obtained by electroerosive dispersion of ZhS6U waste in water

The results of experimental studies aimed at optimizing the process of spark plasma sintering of powders obtained by electroerosive dispersion of waste heat-resistant nickel alloy ZhS6U in distilled water are presented. Optimal values of pressure, temperature and holding time of spark plasma sintering of electroerosive nickel powders providing a nonporous structure of a heat-resistant alloy with maximum hardness have been established.

Халькогениды висмута, полученные различными методами

The microstructure and thermoelectric properties of a Bi2Te3–Bi2Se3 solid solution samples containing 20 mol. % Bi2Te3 doped with Hg2Cl2 of n-type conductivity obtained by hot pressing, extrusion and spark plasma sintering of powders prepared by melt spinning and grinding the ingot in a ball mill were studied. Optical and electron scanning microscopy methods were used. The effect of the disk rotation speed on the morphology of particles obtained by melt spinning is investigated. The Seebeck coefficient, electrical conductivity and thermal conductivity were measured at room temperature and in the temperature range 100 – 700 K and the thermoelectric figure of merit was calculated. The samples had anisotropy of electrical conductivity (σ) and thermal conductivity (κ) in the direction perpendicular and parallel to the pressing, the Seebeck coefficient (α) was isotropic. At 300 K anisotropy factors σ┴/σ// ~ 2, κ┴/κ// ~ 2, α┴/α// ~ 1. The highest thermoelectric figure of merit (ZT)max = 1,0 ± 0,1 at ~ 470 K was obtained for extruded samples from powders prepared by grinding the ingot and for hot-pressed samples from powders obtained by melt spinning.

Superhard single‐phase (Ti,Cr)B2 ceramics

AbstractA nominally pure and dense (Ti0.9Cr0.1)B2 ceramic was produced by spark plasma sintering of powders synthesized by boro/carbothermal reduction of oxides. The synthesized powders were a single phase and had an average particle of 0.4 ± 0.1 μm and an oxygen content of 1.2 wt%. Average Vickers hardness values of the resulting ceramics increased from 25.9 ± 0.8 GPa at a load of 9.81 N, to 46.3 ± 0.8 GPa at a load of 0.49 N. Compared to the nominally pure TiB2 ceramic obtained under the same processing conditions, the (Ti0.9Cr0.1)B2 ceramic had higher values under the same load due to the finer average grain size (2.4 ± 1.0 μm), higher relative density, and solid solution hardening. The results indicated that the Cr addition promoted densification, suppressed grain growth, and improved the hardness of TiB2 ceramics. This is the first report for dense and single‐phase (Ti,Cr)B2 ceramics as superhard materials.

An investigation on diffusivity while achieving a cylindrical aluminide coating on metals using simultaneous spark plasma sintering of powders

Simultaneous spark plasma sintering (SPS) of metal powders (Fe and Ni) with their respective aluminide powders (FeAl and NiAl) was attempted to produce a cylindrical aluminide coating on a cylindrical metal core. The interdiffusion zone (IDZ) formed between the metal and the aluminide was analyzed to evaluate the diffusion coefficient. The composition variation and the actual temperature estimated at the interface were taken into consideration while evaluating the diffusion coefficient. The diffusion coefficients estimated based on the IDZ are found to be higher than those obtained by conventional methods but are in agreement with those obtained from previous SPS studies.

Creep behavior and postcreep thermoelectric performance of the n-type half-Heusler alloy Hf0.3Zr0.7NiSn0.98Sb0.02

When subjected to uniaxial compressive stresses at 600°C, the n-type ZrNiSn-based half-Heusler alloy Hf0.3Zr0.7NiSn0.98Sb0.02 exhibits Newtonian flow, consistent with diffusional creep of its fine-grain (1–7 μm) microstructure achieved via spark-plasma sintering of powders. In addition to its promising thermoelectric performance at high temperatures, this alloy can sustain very high compressive stresses at 600°C (from 21 to 359 MPa, for ~ 23 days) without macroscopic failure. However, the brittle nature of the alloy leads to the formation of numerous cracks at such high stresses, which in turn deteriorate the thermoelectric performance. Among thermoelectric materials mechanically tested at high temperature to date, the present ZrNiSn-based half-Heusler alloy has the highest creep resistance. Given their high melting temperature, stiffness, and creep resistance, half-Heusler alloys appear very well suited for long-term thermoelectric applications where high stresses and temperatures are present.

Part 2. Structure, mechanical and thermophysical properties of consolidated ceramics based on (Hf,Ta)B2

(Hf,Ta)B2-based ceramics were produced by hot pressing (HP) and spark plasma sintering of powders obtained by combustion synthesis in Hf-Ta-B system. The dense ceramics possess exceptionally high hardness (60–70 GPa) and Young's modulus (584 GPa). The thermal conductivity is 30.3–52.9 W/m K depending on the phase composition. Plasma torch testing of the single- and two-phase (Hf,Ta)B2-based ceramics at 1500–2500 °C demonstrated the formation of a protective multi-layer oxide film with good adhesion to the ceramic, which increases the enthalpy of decomposition of ceramics up to 390 kJ/g.

Homogenization of Biporous Agglomerated Powder Structures During High‐Temperature Consolidation

Specifics of agglomerate densification—important for hot pressing, conventional, and spark plasma sintering of powders—are analyzed based on the biporous material modeling framework. Numerical simulations are utilized to determine what technological parameters can be used to improve the postprocessing homogeneity of agglomerated powder‐based materials. The modeling results indicate that the homogenization during sintering and hot pressing of agglomerated nano‐ and micrometer‐size powders is significantly impacted by the viscosity of grain‐boundary sliding and by the possible existence of high‐intensity diffusion paths along the agglomerate boundaries.

Hot forging of Ti–6Al–4V alloy preforms produced by spark plasma sintering of powders

Powder preform forging is a technology that comprises the preparation of near net shape preforms through powder metallurgy and a subsequent hot forging in order to obtain the desired final shape. In this work, two Ti–6Al–4V powder preforms were sintered through spark plasma sintering (SPS) and then hot compressed in a horizontal dilatometer. Varying the temperature of the process, two full density preforms having different microstructures were produced: sintering at 950°C, a plate-like α was obtained, whereas sintering at 1050°C, an acicular α was obtained. The behaviour of the preforms under hot forging has been studied through hot compression tests carried out in a quenching and deformation dilatometer in a range of temperature and strain rates typically used in hot forging this alloy (850–1050°C, 0·01–1 s−1). Hot workability has been evaluated by measuring the stresses required for deformation and by analysing both the stress–strain curves recorded during testing and the microstructures after deformation. The main microstructural phenomena occurring during hot compression were individuated. The best conditions for the hot forging operation of SPS preform are temperatures above β transus, where the materials are deformed in a regime of dynamic recrystallisation, at every strain rate.

Low temperature spark plasma sintering of YIG powders

A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 °C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 °C leads to dense samples with minimal formation of YFeO 3, opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption.

Nanostructured/ultrafine multiphase steel with enhanced ductility obtained by mechanical alloying and spark plasma sintering of powders

A nanostructured/ultrafine steel with a complex microstructure comprising bainitic ferrite, austenite and martensite was obtained by mechanical alloying and spark plasma sintering of powders. Transmission electron microscopy and X-ray diffraction analysis were employed to investigate the microstructural morphologies and the nature of bainitic ferrite and retained austenite formed during sintering process. The presence of a complex microstructure with elongated ferritic lamellae separated by thin layers of retained austenite was revealed. Some ferritic equiaxed grains are also present. The steel displays a large uniform plastic deformation, thanks to its work hardenability provided by the microstructural characteristics: the bimodal distribution of ferrite, the multiphase microstructure and the TRIP phenomenon provided by austenite.

Low-temperature synthesis of high-purity Ti 3AlC 2 by MA-SPS technique

Ternary carbide Ti 3AlC 2 was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS) from elemental powder mixtures of Ti, Al and C, and the effect of Al content on formation of Ti 3AlC 2 during both processes was investigated. The results showed that adding proper Al content in the staring materials significantly increased the phase purity of Ti 3AlC 2 in the synthesized samples. Dense and high-purity Ti 3AlC 2 with <1 wt.% TiC could be successfully obtained by spark plasma sintering of powders mechanically alloyed for 9.5 h from a starting powder mixtures of 3Ti/1.1Al/2C at a lower sintering temperature of 1050 °C for 10–20 min.