Thermal transitions in metastable Cu – 68.5 at. % Co alloy.

Arc melted and drop tube processed Cu – 68.5 at. % Co alloy has been subjected to differential thermal analysis (DTA). The liquidus temperature determined from the DTA curves in the arc melt sample (1664 K) was found to be close to phase diagram estimate of 1662 K. In contrast as a result of liquid phase separation in the drop tube samples, the values obtained in the powders were much lower mainly because the compositions of the demixed phases vary from that of the parent melt. The liquidus temperature of the 850 + μm powders was 1632 K while that of the < 38 μm sieve size powder was 1616 K. This variance is due to the asymmetric nature of the metastable phase diagram of the system.

Karakterisasi Serbuk Timah dari Sistem Atomisasi Gas Argon Panas - Sub Sistem Gas Alir Tabung Gas

<p class="Abstract">The tin powder was used in some applications and technology such as for part manufacture through alloying, pressing, and sintering process, mixing material for the pyrotechnic application, the main material for solder pasta, mixing material on tin chemical, and others. Therefore, the demand for tin powder with a small size, spherical shape, and high purity is increasing severely. Indonesia (PT. Timah Tbk.) is one of the world’s largest producers of tin raw materials. This raw material can be processed be as powder by the atomization method. In this research, hot argon gas atomization system was used to generated tin powder. Raw tin was melted in a melting chamber with temperature variations of 600, 700, 800, and 900 °C. This experiment generates powder with a dominant size of 37 – 150 mm. Meanwhile, for size powder of 0 – 30 mm, dominated by size range of 0 – 10 mm. Furthermore, the size powder of 0 – 30 mm is composed of tin phase, without tin oxide. The tin powder of melting chamber temperature of 900 °C produces the largest tin powder with a size of 0 – 10 mm and spherical powder.</p>

Pressure Induced Stability Enhancement of Cubic Nanostructured CeO2 †

Ceria (CeO2)-based materials are widely used in applications such as catalysis, fuel cells and oxygen sensors. Its cubic fluorite structure with a cell parameter similar to that of silicon makes it a candidate for implementation in electronic devices. This structure is stable in a wide temperature and pressure range, with a reported structural phase transition to an orthorhombic phase. In this work, we study the structure of CeO2 under hydrostatic pressures up to 110 GPa simultaneously for the nanometer- and micrometer-sized powders as well as for a single crystal, using He as the pressure-transmitting medium. The first-order transition is clearly present for the micrometer-sized and single-crystal samples, while, for the nanometer grain size powder, it is suppressed up to at least 110 GPa. We show that the stacking fault density increases by two orders of magnitude in the studied pressure range and could act as an internal constraint, avoiding the nucleation of the high-pressure phase.

Laser Re-Melt Technique for Laser Additive Repair of Narrow Rectangular Cracks in Grade 5 Titanium Alloy (Ti-6Al-4V)

Groove inaccessibility, top groove powder impedance, irregular sidewall powder delivery and lack of sidewall vertical irradiation have been reported as major limitations for the use of Laser Additive Technology (LAT) for narrow rectangular crack repair applications. As a result, most reported repair attempts were concluded unsuccessful. In the present work, a multi-track laser re-melt technique was developed for the repair of narrow rectangular cracks of sizes 2 and 3 mm, both 5 mm deep on 7 mm thick Ti-6Al-4V plates. The laser re-melt technique was carried out at controlled laser power, focal length, spot size, powder feed rate, gas flow rate and scanning speed. The repaired substrates were evaluated for defects through optical microscopy (OM) and scanning electron microscopy (SEM). The obtained results showed densely fused defect-free repaired substrates with good evolving microstructure.

Microstructure and Mechanical Properties of Fe/MgO Micro-Nano Composite for Electrotechnical Applications

The composite based on the microns iron size powder and MgO nanopowder was prepared using pressing followed by conventional and microwave sintering. Microstructure of the composite was investigated to evaluate the changes induced by different sintering technology. Young’s modulus, flexural strength and hardness of composites were analyzed to investigate the mechanical properties in dependence on MgO content, as well as in dependence on the sintering method. Microstructure and mechanical properties as well as functional magnetic properties of prepared composites are discussed in the paper. The main benefit of microwave heating found within process time shortening was confirmed in the case of the microwave sintered Fe/MgO composite.

Production of sinters from commercial powder mixtures for a matrix of diamond impregnated tools

The paper presents the results of analyzing mechanical properties of the sinters obtained from the commercial iron-based powder mixtures. Parameters mechanic, plastic and density, hardness and porosity of the sinters were determined. The sinters microstructure and the chemical composition analysis were carried out by using the scanning electron microscope. The results were compared with the properties of the sinters obtained from the cobalt SMS (submicron size) powder.

Chemical, Thermal and Phase Analysis of Malaysia’s Electric Arc Furnace (EAF) Slag Waste

This study aims to characterize and investigate properties of EAF slag waste obtained from Southern Steel Berhad, Penang (one of Malaysia’s largest steel makers), prior to its recycling into valuable products. Before characterization, lump form of the EAF slag was crushed into micron size powder. The properties investigated were loss of ignition (L.O.I.), chemical composition, leaching behavior, thermal properties and mineral phases present. Through XRF characterization, the chemical composition of the EAF slag was obtained. The slag was found to have extremely low L.O.I. (0.01 wt.%). Leaching test proved the slag is non-hazardous and safe to be handled. Meanwhile, thermal analysis (TGA) revealed the EAF slag is thermally stable and unlikely to decompose upon heating. Phase identification and quantification were performed by applying Rietveld refinement method. The EAF slag consisted of gehlenite (Al2O3.2CaO.SiO2 – 45.3 wt.%), larnite (2CaO.SiO2 – 21.0 wt.%), hematite (Fe2O3 – 13.4 wt.%) and wustite (FeO – 20.3 wt.%) mineral phases. The XRD profile fitted well with agreement indices of the refinement (Rwp: 6.658 and GOF: 2.588). The properties investigated in this study are expected to shed lights in evaluating the potential recycling of the EAF slag into various valuable products such as aggregate, brick, ceramic tile and cementing material.