Effects of Magnesium Content on Structure and Electrochemical Properties of La-Mg-Pr-Al-Mn-Co-Ni Hydrogen Storage Alloys

The discharge capacity, microstructures, and corrosion resistance of some as-cast alloys represented by the formula La0.7−xMgxPr0.3Al0.3Mn0.4Co0.5Ni3.8, where x = 0.0, 0.1, 0.3, 0.5, and 0.7, were investigated by SEM/EDX, XRD, and electrochemical measurements. The partial substitution of La by Mg refined the grain structure while the total substitution changed it from equiaxed to columnar. Three phases were detected: a major phase (M), a grey phase (G), and a dark phase (D). The compositions analyzed by EDX suggested that the M phase was close to a LaNi5 phase. With the increase of the Mg content, the analyses revealed a G phase with composition close to a RMg2Ni9 (R = La,Pr) and a D phase close to a MgNi2 phase. The XRD analysis and Rietveld refinement corroborated the EDX results. The corrosion resistance of the alloys was evaluated in 6.0 mol·L−1 KOH solution, and the results showed that the substitution of La by Mg was beneficial for this alloy property. Nevertheless, Mg addition was deleterious to the discharge capacity of the electrodes.

Structure and Property Stability of Rapidly Solidified In-Sn γ-Phase Alloy

The crystallization characteristics of the binary alloys which have InSn4 intermetallic compounds(IMC) were investigated.The influence which high undercooling had caused to the process of lattice formation,the lattice evolution in the later period of solidification,the stabilization process of the alloy property were mainly studied.The results show that the solute redistribution is restrained intensely in the rapidly solidified condition,the components of InSn4 IMC distribute uniformly,the highly undercooling structure have small sub-grain structure.X-ray diffraction analysis show that strong (0001) texture is formed in the alloys,EBSD analysis show that many sub-boundaries exist in the grains.While these unstable structures have an isothermal annealing between 20~140oC,the texure feature of the alloys weaken,and at the same time the microhardness lower in varying degrees.

An Overview of Advanced Ni-Base Superalloys for Small Turbines and Missile Engine Applications

Ni-base superalloy cast materials provide an outstanding balance of high temperature strength, fatigue resistance, oxidation resistance and coating performance and can be produced to very tight tolerances in extremely complex configurations, such as axial and centrifugal integral cast turbine wheels. As a result, cast superalloys are used in the most demanding applications of aero and industrial gas turbine engines. Use of these materials is expanding to smaller microturbine, turbojet, turbocharger and missile engine applications due to this unique combination of desirable properties. This paper will present an overview of the application of investment cast Ni-base superalloys and process capability to small turbine and missile engines. Alloy property data will be presented, including advanced equiax alloys CM 247 LC®, CM 681 LC® and CM 939 Weldable®, directionally solidified alloys CM 247 LC and CM 186 LC® and single crystal alloy CMSX-4®, along with typical or candidate applications for each.