Calcium-containing Alloys Research Articles

Enhanced mechanical properties of as-cast Mg-Al-Ca magnesium alloys by friction stir processing

Friction stir processing (FSP) of as-cast Mg-7Al, Mg-4Al-3Ca (AX43), and Mg-2Al-5Ca (AX25) magnesium alloys led to the remarkable grain refinement and enhancement of mechanical properties. This is due to the replacement of the interconnected, brittle constituents with uniformly dispersed fine particles after FSP. Due to the presence of thermally-stable Al-Ca intermetallics, the calcium-containing alloys showed more intense grain refinement compared to the Mg-7Al alloy with unstable Mg17Al12 phase. The friction stir processed AX43 alloy with a grain size of 1.7 μm exhibited the best tensile properties.

Effect of calcium on the electrochemical behaviors and discharge performance of Al–Sn alloy as anodes for Al–air batteries

The effect of calcium on the microstructure, electrochemical behaviors and discharge properties of Al–0.1Sn alloys as anodes for alkaline Al–air batteries are investigated. Addition of calcium to Al–0.1Sn alloys promotes the precipitation of CaSn phase and Al4Ca phase in the matrix. The Al–0.1Sn alloys with calcium (≤ 0.16 wt%) exhibit better discharge performance and higher anode efficiency, which is due to the oxidation of CaSn phases introducing one layer of Ca(OH)2-containing film that inhibits the hydrogen evolution reaction of the anode. The Al–0.1Sn–0.08Ca alloy shows a discharge capacity as high as 2495.75 Ah kg−1 (83.75% anode efficiency) and a peak energy density of 3793.54 Wh kg−1 at 20 mA cm−2, which are 24.8% and 18.9% higher than for the Al–0.1Sn alloy. By contrast, the Al4Ca phase formed by excessive calcium strongly aggravates the hydrogen evolution reaction of the Al–0.1Sn alloy, which is not conducive to its discharge performance. Furthermore, at high current densities, the discharge behaviors of calcium-containing alloys are significantly suppressed by the Ca(OH)2-containing film. Therefore, the Al–0.1Sn–0.08Ca alloy is suitable to serve as anode materials for Al-air batteries at low current densities.

Thermodynamic analysis of deoxidizing ability of strontium in liquid iron: phase stability diagram IN Fe-Sr-O and Fe-Mg-Sr-O systems

Strontium is considered to be a promising element-deoxidizer and a modifier of steels and alloys, especially in barium and calcium-containing alloys. However, the thermodynamics of its interaction with oxygen in liquid iron is not studied enough. The aim of the study is a thermodynamic analysis of the deoxidizing ability of strontium in liquid iron of the Fe-Sr-O and Fe-Mg-Sr-O systems using a method for constructing the surface of the solubility of components in a metal (SSCM). SSCM is a diagram linking the compositions of a liquid metal with the compositions of the products of interaction formed during deoxidizing. At the calculation, the chemical reactions occurring in the melt of the Fe-Sr-O and Fe-Mg-Sr-O systems and the equilibrium constants of these reactions, including the formation of liquid and solid strontium oxides from the components of the metal melt, were established. The first-order interaction parameters (according to Wagner) of strontium with oxygen and magnesium in liquid iron were determined. The oxygen solubility isotherms were constructed in the Fe-Sr-O systems (within the temperature range 1550-1650 °С) and FeMg-Sr-O (for the temperature 1600 °С). The maximum deoxidizing ability of strontium in liquid iron was determined. It was established that in comparison with magnesium, strontium is a weaker deoxidizer.

Experimental Study of Refining and Modification of Steel with Si–Ca, Si–Sr, and Si–Ba Alloys

The results of thermodynamic calculations and experimental studies of the deoxidation, desulfurization, and modification of low-carbon steel with aluminum and Si–Ca, Si–Sr, and Si–Ba alloys are presented. The metal treatment with silicocalcium leads to the formation of corrosive non-metallic inclusions (CANI). The replacement of calcium-containing alloys with Ba and Sr alloys helps to clean steel from CANI, the formation of smaller complex oxysulfide non-metallic inclusions and a change in the grain size of metal. The calculated data are consistent with the experimental results.

Eutectic alloys based on the Al–Zn–Mg–Ca system: microstructure, phase composition and hardening

The experimental study of aluminium alloys based on the Al–Ca–Zn–Mg system (3.5% Mg and 2.5% Mg, 0–10% Ca, 0–14% Zn (wt-%)) was combined with Thermo-Calc simulations for the optimisation of the alloy composition. Zinc is distributed between aluminium solid solution and phase (Al,Zn)4Ca. Magnesium was not observed in the intermetallic phase. The eutectic (Al,Zn)4Ca had fine structure and particles of (Al,Zn)4Ca were capable of spheroidisation during the heat treatment at 520°С. The maximum level of hardness observed in calcium-containing alloys was higher than 200 HB, suggesting good strength properties. With an example of the Al–Zn(9%)–Mg(3.5%)–Ca(3%) alloy, the possibility of manufacturing thin rolled sheets based on the (Al)–Ca eutectic was demonstrated.This article is part of a Themed Issue on Aluminium-based materials: processing, microstructure, properties, and recycling.

Challenges and Solutions in the Development of Magnesium Sheet for Sustainable Vehicle Concepts

Magnesium as the lightest structural metal offers significant potential weight saving compared with steel and aluminium. Cast magnesium components are widely used, e.g. as engine blocks or gear box housings. To open more opportunities for weight saving, it is necessary to widen the application fields to wrought products, such as large thin walled components for which sheets as semi-finished products are needed. The production and processing of magnesium sheets material is currently hampered by the limited formability of magnesium and high costs. The use of the twin-roll casting (TRC) as a cost-effective manufacturing process and the development of new calcium-containing alloys are leading to a decisive reduction of those obstacles.

Development of a magnesium alloy with good casting characteristics on the basis of Mg–Al–Ca–Mn system, having Mg–Al2Ca structure

Application of calcium as alloying element for magnesium alloys has been considered according to literature data. Mg–7%Al–4%Ca–0.5%Mn casting alloy was offered, which possesses the low propensity to the hot brittleness and good castability. The alloy has the moderate strength (σu = 150 MPa) and the satisfactory percentage elongation (δ = 3%). It is shown, that calcium-containing alloys smelting of Mg–Al–Ca–Mn system is preferable with the application of low-chloride flux FL10 (20%MgCl2; 29%KCl; 12%BaCl2; 23%CaF2; 15%MgF2; 1%B2O3). The alloy smelting in the atmosphere of argon and SF6 mixture results in the increased shelling and waste of calcium. The heat treatment is offered for the developed alloy, which is directed to the Al2Ca phase spheroidizing. The developed magnesium alloy, alloyed with calcium, is perspective for the industry production of low-cost moulding.

The influence of calcium and cerium mischmetal on the microstructural evolution of Mg–3Al–1Zn during extrusion and resulting mechanical properties

The role of calcium and rare earth elements containing particles in magnesium alloys during extrusion in the temperature range T = 250–350 °C is studied by optical metallography and texture measurements. A reduction of the final grain size after extrusion, mainly caused by the influence of intermetallic particles is observed, which becomes more distinct for higher alloying contents and low extrusion temperature. The smallest mean grain size ( D mean = 8 μm) could be observed in a AZ31 + 0.4% Ce mischmetal + 0.8% Ca alloy after extrusion at T = 250 °C. The extruded rods exhibit a { 1 1 2 ¯ 0 } + { 1 0 ¯ 1 0 } -fiber texture ( c-axes in the radial direction) with a high tension–compression asymmetry of the yield stress in the extrusion direction. The influences of the alloying contents on the texture evolution are discussed in terms of the activation of non-basal slip modes at higher temperatures and the mechanisms of dynamic recrystallization. The textures are distinctly influencing the mechanical properties. The combination of texture and particle hardening is leading to improved strength of calcium-containing alloys.

Evaluation of cyclic voltammetry for accelerated corrosion life tests of the PbO 2 electrode

Cyclic voltammetry, electrochemical measurements at constant potential, and metallography were used to follow the anodic activity of chill-cast and wrought pure Pb and ternary PbCaSn alloys as well as cast and wrought PbSb. Cyclic voltammetry showed the formation of irreversible PbO 2 during a 1000 cycle test and also brought to light a diffusion or barrier-limited process during the cathodic discharge of calcium-containing alloys. Constant potential measurements could be correlated with corrosion behavior. The relative anodic activity was ranked for all samples tested. In general, chill-cast material showed less anodic activity than wrought materials, and ternary alloys less than pure lead, although in some cases the difference was very small.