Papers by Keyword: Vacuum Induction Melting

Abstract: In 2006, J. Sato et al. discovered the L1₂ gamma-prime phase in the Co-Al-W alloy system. Since that time there has been a significant academic effort to characterize and understand the thermodynamics, the structure, and properties of alloys in this system. That work has shown that such alloys have promise as next generation high temperature materials due to the ability to engineer a high gamma-prime content alloy with a higher gamma prime solvus and higher melting point than many Ni-base gamma-prime strengthened alloys. Furthermore, a relatively narrow range of solidification temperature and large range of temperature between the gamma-prime solvus and the solidus are two characteristics that suggest cast and wrought versions of the alloys should be able to be manufactured routinely. However, to date all published research has been on small, laboratory scale samples typically less than about 2 kg, cast and hot rolled or cast as single crystals. This paper describes ATI’s experience in assessing the feasibility of manufacturing a cast and wrought billet product in the Co-Al-W-X alloy system. Three 22 kg heats were produced to examine a small range of alloy compositions of potential commercial interest: Co-9Al-9W, Co-9Al-9W-2Ti, and Co-9Al-9W-2Ti-0.02B, respectively. Each heat was vacuum induction melted and vacuum arc remelted. The as-cast microstructure will be presented. Ingots were homogenized and hot worked. The microstructure at various stages of production are shown and hot working behavior is described.

Abstract: Mg2-xNdxNi (x=0.1, 0.2, 0.3) alloys, along with Mg2Ni for comparison, were prepared by vacuum induction melting, The influent of content of Nd on the microstructure and hydrogen storage performance were studied, the hydrogenation mechanism of Mg2-xNdxNi alloys was explored. The results showed that: the hydriding-dehydriding kinetics performance of Mg2Ni were improved by adding Nd, but the hydrogen storage capacity of alloys decreased. Mg2Ni, Nd2Ni7, NdMg12, Nd5Mg41 and other minor phases were observed in Mg-Nd-Ni alloys. Mg-Nd-Ni alloys had favorable kinetics performance. Compared with Mg2Ni alloy, the desorption rate and desorption ratio decreased with the increase of the amount of Nd, the hydriding-dehydriding kinetics performance Mg1.9Nd0.1Ni was the best. The hydrogenation mechanism of Mg2-xNdxNi alloy was nucleation and grown up mechanism controlled by diffusion ([-ln(1-ξ)]n=kt), the nucleation and grown up process was decided by the diffusion of hydrogen atom in alloy. Hydrogenation rate increased with the increase of hydrogen pressure and adding Nd, it was because the diffusive rate of hydrogen atom in alloy increased. According to the analysis of kinetics mechanism, methods to improve kinetics performance was put forward by reducing the diffusion path of hydrogen atom in alloy.

Abstract: A novel technique of pure Lithium addition has been adopted for the processing of Al-Cu-Li alloy AA2195 cast ingots (7-8 kg each) in VIM under dynamic inert atmosphere, which gives more than 95% recovery of Lithium. The cast billets were homogenized, forged and converted into 12mm diameter rods by caliber rolling in the temperature range of 250°C, 300°C, 350°C and 400°C. The caliber rolled rods were treated to T8 (Solution Treatment+WQ+CW+Aging) condition. Mechanical properties were evaluated for T8 tempered bars at room temperature and correlated with microstructural observations. Highest mechanical properties in T87 temper have been obtained for rods caliber rolled at 350°C temperature.

Abstract: The vacuum induction melting and control solidification is a new developed process for the manufacture of polycrystalline silicon with the advantage of quick heating rate compared to the traditional resistance heating method. The graphite susceptor of the induction furnace plays a key role in controlling the temperature of the melt of polycrystal silicon for solar cells. This paper investigates how different coatings painted on the susceptor would influence the heating efficiency and the temperature distribution of the silicon melt. A graphite susceptor is usually coated with a thin film of insulating material to reduce heat losses and to prevent vapors such as SiO to contaminate the susceptor. Numerical simulations show that the coating material at the outer surface of the susceptor should be the one with low thermal conductivity to prevent heat loss. On the other hand, the coating on the inner surface should be the material with high thermal conductivity to allow easy heat transfer.

Abstract: In this work, the possibility of melting titanium alloys in vacuum induction furnaces in metal and ceramic crucibles and in ceramic crucibles with coatings deposited by the plasma-spray method or by hand using a brush was evaluated. The effect of the crucible material and the coating material on the chemical composition, microstructure and alloy properties was studied. The main criterion for evaluating the suitability of individual crucibles was the content of oxygen in the molten alloys and of impurities remaining as a result of the reaction of the liquid alloy with the crucible and coating material.