[en] The paper presents the results of a corrosion electrochemical study of the effect of calcium addition as a structure modifier on the anodic behaviour of lead babbit (Pb + 15% Sb + 10% Sn + 1.0% Ca) in the medium of 0.3% NaCl electrolyte. The studies were carried out in potentiodynamic mode with a potential sweep rate of 1 mV/s. The addition of calcium to lead babbit (PbSb15Sn10Ca) was 0.01-1.0 wt %. The results show that calcium additions up to 1.0 wt % reduce the corrosion rate of the original alloy by 10-15%. (author)

[en] The paper presents the results of the study of the influence of calcium on the anodic behaviour of the aluminium alloy AlMg5.5Li2.1Zr0.15 of the duralumin type in the medium of 3% NaCl electrolyte. The study of the corrosion-electrochemical behaviour of the alloys was carried out using the potentiostatic method in the potentiodynamic mode with a potential sweep rate of 2 mV/s. It was found that the addition of calcium reduces the rate of anodic corrosion of the starting alloy AlMg5.5Li2.1Zr0.15 by 8-10%. The addition of calcium to the base alloy shifts the basic electrochemical potentials to the positive region. (author)

[en] In the present work, the effect of Ca additions on microstructure and corrosion characteristics of high pressure die-cast Mg-4Al-2Sn alloy has been investigated. Mg-4Al-2Sn-xCa (x= 0, 0.3 and 0.7wt.%) alloy was prepared by using a high pressure die-casting method. Results indicated that the microstructure of Mg-4Al-2Sn alloy consisted of α-Mg, Mg_1_7Al_1_2 and Mg_2Sn phase. With increase of Ca additions, CaMgSn phase was newly formed and grain size was sharply decreased. From the test results, the corrosion resistance of die-cast Mg-4Al-2Sn alloy was significantly improved by Ca addition. It is considered that stabilization of Mg(OH)_2 layer and refinements of microstructure with increase of Ca additions.

[en] A scheme reflecting the relationship between fluorite, fluorite-like superstructures and solid solutions with intermetallides Ca₈In₃, Mg₅Ga₂ and relative compounds is proposed. It is shown that the structural mechanism of interstition of additional metal atoms to the ratio of components 2:1 in intermetallides is identical to that of interstition of F atoms, proposed for fluorite-like solid solutions MF_2+x, based on substitution of M₄F₂₃ clusters for M₄F₂₆ ones

[en] This paper investigated the effect of calcium addition on the formation and properties of aerobic granules under high (conventional SBR) and low (simultaneous fill/draw SBR) selection pressure. Additionally, the simultaneous removal of carbon, nitrogen, and phosphorus, and the operational stability were assessed. The conventional SBRs showed earlier granule development (20 days) than the simultaneous fill/draw SBRs. The effect of calcium on granulation was more accentuated in conventional SBRs, forming larger granules in a shorter interval of time due to the higher EPS production. Additionally, higher amounts of calcium were found in the EPS matrix, mainly during the formation of granules. The operation regime and the addition of calcium did not affect the removal of carbon, nitrogen, and phosphorus. However, they both influenced the granulation time, settleability characteristics, size, and granule composition.

[en] The aim of the present paper is to give a theoretical interpretation of the decreasing dispersion law. Recently, the dispersion of short-wavelength collective density fluctuation in a metallic glass (Mg₇₀Zn₃₀) for momentum transfer near the first maximum of the static structure factor was measured by using inelastic neutron scattering, and the result showed a decreasing dispersion relation. The steps of calculation of the dynamical properties of a disordered material are calculation of interatomic forces, calculation of the equilibrium atomic structure, and the presentation of the one-phonon contribution to the symmetrized dynamical structure factor S(Q,W). In the case of amorphous simple metal alloys, central effective pair potential may be derived from a first principle pseudopotential theory. The total vibrational density of states (TDOS) was calculated and compared with the measured one by inelastic neutron scattering. The theory gave a good overall description. The theory describes the falling dispersion law well. The idea that the falling dispersion law originates from a diffuse Umklapp scattering by long-wavelength acoustic modes was presented, and the argument is described. (Kato, T.)

[en] Effects of trace elements (0.2Y and 0.2Ca (wt%) on the eutectic Ge in high purity Al–20Ge (wt%) alloys were investigated by multi-scale microstructure characterization techniques. Particularly, the distribution of trace elements (Y and Ca) within the eutectic Ge and/or at the interface between eutectic Ge and eutectic Al was investigated by atomic resolution high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) imaging and atom probe tomography (APT). The combined investigations indicate Al–Y and Al–Ca co-segregations. Such co-segregations change significant morphology and growth of the eutectic Ge. In addition, large Al_2Ge_2Y and Al_2Ge_2Ca phases were also measured. The modification of eutectic Ge is discussed in terms of previously postulated modification mechanisms: twin plane re-entrant edge growth mechanism, impurity-induced twinning, and growth restriction of eutectic Ge.

[en] Effects of alloying additions on deformation texture in Mg sheet alloys are still controversial. In this study, a quasi-in-situ electron backscatter diffraction method is used for the first time to monitor the texture evolution during the cold rolling process of Mg–Zn–Ca and Mg–Zn alloys. It is found that the Ca addition does not cause any texture weakening effect — it only delays the development of a strong basal texture by reducing the growth of deformation twins

[en] Highlights: ► Grain refinement of Ca addition in a twin-roll-cast Mg–3Al–1Zn alloy was investigated. ► Addition of 0.08 wt% Ca into Mg melts can significantly reduce the grain size to 30 μm from 100 μm. ► Al₂Ca intermetallic particles have high potency to act as heterogeneous nucleation sites for α-Mg. - Abstract: Addition of 0.08 wt% Ca into AZ31 melts significantly reduces the average grain size of thin strips produced by twin-roll-cast to 30 μm from 100 μm. Like Zr, due to the high chemical activity, the Ca added into the melts reacts with Al and forms Al₂Ca intermetallic compound. X-ray diffraction result approves the existence of Al₂Ca in the thin strips, which formed in the melts. Crystallographic examination of relationship between Al₂Ca and Mg using the edge-to-edge matching model indicates that Al₂Ca particles are effective inoculants for heterogeneous nucleation of Mg. It is considered that Al₂Ca is a potential and effective grain refiner for Mg alloys and the grain refinement through addition of Ca in the AZ31 alloy is attributed to the inoculation effect of Al₂Ca particles formed in the melts.

[en] Highlights: • A good correlation was observed between R_CT and corrosion rates. • An apparent Stearn-Geary coefficient (85 mV) via the correlation was calculated. • The inductive contribution to the EIS response changed with time. - Abstract: The corrosion behaviour of an Mg-1Ca alloy in simulated body fluid (SBF) for 14 days was investigated by electrochemical impedance spectroscopy (EIS), hydrogen evolution measurement, weight loss and observation of the corroded alloy surfaces, with the aim of establishing a clear correlation between the values of the parameter obtained from EIS fitting and corrosion rates. It was found that corrosion proceeds in three stages, characterized by differences in the values of resistances and by the weight of the relative contribution of the inductive behaviour to the overall EIS response. Among all the parameters obtained from EIS fitting, only the charge transfer resistance presented a good correlation with the corrosion rate over the whole duration of the measurement, and an apparent Stearn-Geary coefficient could be calculated. Based on the EIS results, a better understanding of the corrosion behaviour of the Mg-1Ca alloy in SBF solution was attained.