High Isostatic Pressing Research Articles

The effect of C and (Er, Sm, Eu)2O3 doping and high isostatic pressing on superconducting properties of MgB2 phase and volume of cylindrical MgB2 ceramic samples

We present our research on the influence of pressure on the synthesis of the MgB2 phase and, consequently, on the superconducting properties of the MgB2 system. We investigated undoped, C-doped, and double-doped, i.e. C and Re2O3 Re = Sm, Eu, Er), MgB2 samples. We conducted comparative studies of critical temperature, irreversibility field, critical current and pinning force for ceramic samples annealed at ambient pressure and 1 GPa. Heat treatment under high isostatic pressing (HIP) of 1 GPa reduced the volume of the undoped MgB2 cylinder by 40%. This significantly increases the density, homogeneity and number of connections between the grains, and also eliminates voids in the undoped material. However, we did not observe any reduction in the volume of C-doped and double-doped MgB2 cylinders. Our research shows that the critical parameters of the MgB2 superconductor can be increased more effectively by doping C and the HIP process than by double doping C with Er, Sm or Eu and the HIP process. The HIP process improved the efficiency of pinning centers created by magnetic admixtures with a low magnetic moment (Sm and Eu), but on the other hand, reduced this efficiency for admixture with a high magnetic moment (Er).

Additive Manufacturing of High-Entropy Alloys: A Review.

Owing to the reduced defects, low cost, and high efficiency, the additive manufacturing (AM) technique has attracted increasingly attention and has been applied in high-entropy alloys (HEAs) in recent years. It was found that AM-processed HEAs possess an optimized microstructure and improved mechanical properties. However, no report has been proposed to review the application of the AM method in preparing bulk HEAs. Hence, it is necessary to introduce AM-processed HEAs in terms of applications, microstructures, mechanical properties, and challenges to provide readers with fundamental understanding. Specifically, we reviewed (1) the application of AM methods in the fabrication of HEAs and (2) the post-heat treatment effect on the microstructural evolution and mechanical properties. Compared with the casting counterparts, AM-HEAs were found to have a superior yield strength and ductility as a consequence of the fine microstructure formed during the rapid solidification in the fabrication process. The post-treatment, such as high isostatic pressing (HIP), can further enhance their properties by removing the existing fabrication defects and residual stress in the AM-HEAs. Furthermore, the mechanical properties can be tuned by either reducing the pre-heating temperature to hinder the phase partitioning or modifying the composition of the HEA to stabilize the solid-solution phase or ductile intermetallic phase in AM materials. Moreover, the processing parameters, fabrication orientation, and scanning method can be optimized to further improve the mechanical performance of the as-built-HEAs.

The effect of Ar-ion irradiation on nanomechanical and structural properties of ODS RAF steels manufactured by using HIP technique

The influence of low energy ion irradiation on mechanical and structural properties of Oxide Dispersion Strengthened (ODS) Reduced Activation Ferritic (RAF) steels were investigated using Nanoindentation (NI), High Resolution Scanning Electron Microscopy (HR SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques. ODS samples were manufactured by means of High Isostatic Pressing (HIP) technique and irradiated at room temperature with 320 keV Ar2+ ions up to fluences reaching 1 × 1016 cm−2. The results revealed fast increase of nanohardness in the function of two dependencies: (i) vanadium addition and (ii) ion fluence range. Furthermore, along with increasing vanadium content, the increase in the number of ∼100 nm sized precipitates consisting of Cr-O-V and Cr-C-V with small amounts of alloying elements (Ti, Al, W) have been observed. Simultaneously, the presence of nano-precipitates, with average size below 10 nm has been recorded. Conducted research confirms that their number decreases with increasing V content. The reported hardening effect is most probably related to: (i) quantity and size of precipitates identified as chromium-vanadium oxides and carbides with addition of alloying elements and (ii) level of damage created by ion irradiation.

Preparing tin-doped indium oxide ceramic bulk via explosive consolidation and sintering of nanopowders

The tin-doped indium oxide (ITO) ceramic ultra-dense target is the crucial material in spurting preparation of optical-electric films. The difficulty in target fabrication is due to ITO decomposing at high temperatures. In this paper, commercial ITO nanometer powders are used and are explosively shock consolidated with two different sets and different explosives. Experiment data indicate that the shock velocity should be less than 4000 m/sec, and the shock pressure should be more than 6 and even 12 GPa for obtaining good consolidation. The samples are rapidly sintered at a high temperature after shock treatment. A suitable sinter temperature of ITO nanopowders compacted via explosive consolidation (≈1000°C) is determined by a differential thermal analysis. Scanning electron microscope images show that ITO ceramic decomposes and sublimates at a high temperature. The expansion factors of the samples from our experiments and commercial targets obtained by high isostatic pressing (HIP) are measured: α l = 7.81 → 10−6 K−1 for samples sintered at 1000°C, α l = 8.8 → 10−6 K−1 for samples sintered at 900°C, and α l = 6.89 · 10−6 K−1 for HIP samples.

The effect of hot isostatic pressing parameters on microstructure and mechanical properties of Eurofer powder HIPed material

The production of reduced activation ferritic/martensitic (RAFM) steel by powder metallurgy and high isostatic pressing (HIP) offers numerous advantages for different nuclear applications. The objective of this work is to optimise the Eurofer powder HIP process in order to obtain RAFM solid HIPed steel with similar mechanical properties to those of a forged material. Starting from the forged solid Eurofer steel batch, the material is atomized and the Eurofer powder is characterized in terms of granulometry, chemical composition, surface oxides, etc. Different compaction HIP cycle parameters in the temperature range (950–1100 °C) are tested. The chemical composition of the HIPed material is comparable to the initial forged Eurofer. All the obtained materials are fully dense and the microstructure of the compacted material is well martensitic. The prior austenite grain size seems to be constant in this temperature range. The mechanical tests performed at room temperature reveal acceptable hardness, tensile and Charpy impact properties regarding the ITER specification.

Influence of the forming process and sintering conditions on the structure and properties of powder ferrite materials

The effect of uniaxial and high isostatic pressing, and also sintering conditions, on the structure and properties of manganese—zinc, nickel—zinc, and barium ferrites was studied using x-ray, Mossbauer, magnetic, and gravimetric methods of analysis. Isostatic pressing was shown to have a positive effect on the crystallite-porosity structure and specified magnetic properties of the materials investigated.

Sintering of boron carbide and boron carbide-silicon carbide two-phase materials and their properties

Boron carbide is a high-technological ceramic material (it is used for lightweight armor, neutron absorbers, wear pieces, etc.). Hot pressing (2200°C, 40 MPa, Ar atmosphere) and recently high isostatic pressing, are the best known ways for industrial preparation of boron carbide items. Pressureless sintering using metallic, inorganic, B + C, additives is not successful, since, despite having a high density, impurities remain present. Pressureless sintering of boron carbide (or silicon carbide composite) using free carbon addition, produced by in-situ pyrolysis of a Novolaque-type phenol-formaldehyde resin (≈ 9 wt%), is now possible in industry. A promising new method is the use of organic precursors, e.g. polycarbosilane with a small amount of phenolic resin, giving CSi and C by in-situ pyrolysis; the resulting boron carbide ceramics have high density (> 92%) and contain no free carbon and a small amount of SiC (≈ 5 wt%). The mechanical properties of sintered B 4C are close to those of hot-pressed; the SiC dispersion in a B 4C matrix has no toughening effect.