The Phase Constitutes of Ti-Mo-Based Alloys

Ti-Mo-based alloy ingots with different chemical compositions are melted in a vacuum arc furnace under argon atmosphere. The specimens are annealed or water quenched. Heat treatments were carried out in tube-furnace under argon atmosphere. X-ray diffraction (XRD) experiments were performed using a X-ray diffraction apparatus in order to detect the phase constitutes and microstructures of the Ti-Mo-based specimens.

ANALYSIS OF THE METAL MELTING PROCESS IN A VACUUM-ARC FURNACE WITH THE HELP OF ULTRASONIC WAVES

The application of the ultrasonic pulse-echo method of nondestructive testing for measuring the height of the crystallizing ingot and the depth of the liquid metal bath in a vacuum electric furnace during melting is described. An experiment was performed that showed the effectiveness of the proposed solution. This information can be used to control the melting process in similar furnaces.

Effect of scrap using in charge on the microstructure and properties of ZhS6U nickel-based superalloy. Part 2. Structure analysis and mechanical properties of ZhS6U prepared with scrap

The second part of the article considers influence of the scrap amount on structure and mechanical properties of ZhS6U-VI nickelbased superalloy. As the use of scrap is associated with the possibility of alloy contamination by nonmetallic inclusions and loss of alloying elements, the influence of scrap on alloy structure and mechanical properties is in great importance. The samples with diameter of 12 mm were melted in a vacuum arc furnace and were casted into a copper mold from the virgin ZhS6U-VI alloy without scrap and from alloys with 50 % and 100 % of scrap. The alloys structures were investigated using optical microscopy on etched metallographic sections that were cut from the samples’ cross-sections. The studies were carried out on the as-cast samples and the samples after solution heat treatment for 4 hours at 1210 °C. The slightly higher nonmetallic inclusions content were observed in the structure of the alloy melted with scrap in comparison with virgin alloy melted without scrap. For the sample that was melted from 100 % of scrap the inclusions secure level is 3 (ASTM E 45-97) with an average size of inclusions of 28.4 ± 0.2 μm. Herewith the presence of single large inclusions with a size of not more than 70 microns was noted. However, it has no effect on the alloy mechanical properties. Mechanical properties after heat treatment (ultimate strength (UTS) = 1090 – 1100 МPа and elongation (El) = 9 – 11 %) were obtained on the samples melted using 50 and 100 % of scrap and fully correspond to the TU1-92-177-91 standard for ZhS6U-VI nickel-base superalloy. During solidification most of the large nonmetallic inclusions are concentrated under casting surface, which makes their machining difficult. Because of that the use of 100 % scrap without its preliminary processing is not recommended. Acceptable results were achieved when the 50 % of scrap was used.

Investigations into Ti-15Mo-W Alloys Developed for Medical Applications

The β-Ti alloys have attracted the attention of researchers due to their excellent properties and their remarkable biocompatibility. The present study evaluated the mechanical behavior analysis (hardness, compressive strength, and modulus of elasticity) of the Ti-15Mo-W system. For experimental research, we chose the TiMo15 biocompatible alloy as a starting material. In order to improve the mechanical properties, we added tungsten amounts of 3.88 to 12.20 wt.% and analyzed the results obtained. The successive melting of the samples was done using a vacuum arc furnace in a copper crucible cooled with water. Following micro-structural investigations, we found this alloy possessed a homogeneous structure and showed β-phase predominance. The investigated alloys have good mechanical properties—the mean Vickers micro-hardness values are between 251 to 321 HV, the compressive strength values range from 717 to 921 MPa, and the modulus of elasticity is between 17.86 and 45.35 GPa. These results are compatible to the requirements of a metallic material for medical applications as artificial implant devices.

Study on the Viability of the Recycling by Electric Arc Melting of Zirconium Alloys Scraps Aiming the Scalability of the Process

Turning chips of zirconium alloys are produced in large quantities during the machining of alloy rods for the fabrication of the end plugs for the Pressurized Water Reactor (PWR) fuel elements parts of Angra II nuclear reactor (Brazil – Rio de Janeiro). This paper presents a study on the search for an efficient way for the cleaning, quality control and Vacuum Arc Remelting (VAR) of pressed zirconium alloys chips to produce a material viable to be used in the production of the fuel rod end plugs. The process starts with cutting oil clean out. The first step in this process consists in soaking a bunch of chips in clean water, to remove soluble cutting oils, followed by an alkaline degreasing bath and a wash with a high-pressure flow of water. Drying is performed by a flux of warm air. The oil free chips are then subjected to a magnet in order to detect and collect any magnetic material, essentially ferrous, that may be present in the original chips. Samples of the material are collected and then melted in a small non consumable electrode vacuum arc furnace for evaluation by Energy Dispersive X-ray Fluorescence Spectrometry (EDXRFS) in order to define the quality of the chips. The next step consists in the 15 ton hydraulic pressing the chips in a die with 40 mm square section and 500 mm long, producing an electrode with 20% of the Zircaloy bulk density. The electrode was finally melted in a laboratory scale modified VAR furnace located at the CCTM–IPEN, producing 0.8 kg ingots. The authors conclude that the samples obtained from the fuel element industry can be melting in a VAR furnace, modified to accommodate low density electrodes, allowing a reduction up to 40 times the original storage volume, however, it is necessary to remelt the ingots to correct their composition in order to recycle the original zirconium alloys chips. in a process to reduce volume and allow the reutilization of valuable Zircaloy scraps.

Magnetic Properties of Pure Iron with Respect to Different C/Si Ratios and Grain Sizes

Pure iron with C/Si > 1 and C/Si < 1 was smelted by a vacuum arc furnace, and the grain size was controlled through different heat treatments. The microstructure of pure iron was observed by using an optical microscope, and the grain size was subsequently measured and calculated. Finally, the coercive force, saturation magnetic induction, and permeability were measured using a vibrating sample magnetometer. The results indicate that the coercive force increases with decreases in the average grain diagonal size. An increase in the uniformity of the grain increases the saturation magnetic induction. The permeability depends on the average grain diagonal size and the uniformity of the grain as well as the chemical composition of pure iron.