Effect Of Ca Addition Research Articles

Study on the investigation of creep behaviour in squeeze cast Ca-modified AZ91 magnesium alloy

ABSTRACT The AZ91 (Mg-Al) alloy is the most commonly used Mg-cast alloy with high specific strength and excellent die-castability; however, its poor creep performance limits its applications at elevated temperatures. In the present investigation, the effect of Ca addition on the microstructure development and creep performance of squeeze-cast AZ91 alloy recognised as AZX911 alloy has been investigated at 150°C–250°C temperature under 65 and 80 MPa stress. The addition of Ca in the AZ91 alloy results in the precipitation of the thermally stable Al2Ca intermetallic phase, which partially suppresses the precipitation of the thermally unstable β-Mg17Al12 phase and significantly improves the creep resistance of the AZ91 Mg alloy. The governing creep mechanism of AZX911 alloy is found to follow power law creep with n = 3.49 at 150°C that mainly results from dislocation climb. In contrast, a transition to power-law breakdown is observed at 175°C. The resistance to creep deformation of AZX911 further improves with heat treatment at 450°C as compared to the as-cast specimen of the same alloy due to the complete dissolution of the β-Mg17Al12 phase. The activation energy of phase dissolution, estimated using the Kissinger method, is found to be higher (923 kJ/mol) for the Al2Ca intermetallic phase as compared to that for β-Mg17Al12 phase (664 kJ/mol) in AZX911 alloy.

Effect of Ca addition on structure, phase composition and hardness of Al–6 %Cu–2 %Mn sheet alloy

The Al–Cu–Mn–Ca system was proposed as a bases for the design of new group of heat-resistant alloys which can be used for high-temperature applications instead of the 2219 types industrial alloys. Unlike the latter ones, the new alloys also do not require a full cycle of strengthening heat treatment including solid solution treatment, quenching and aging. The effect of calcium addition in the 1–4 wt% range on the structure, phase composition and hardness after high temperature annealing of the Al–6 %Cu–2 %Mn base sheet alloy has been studied. It has been shown that calcium addition leads to the formation of high-temperature eutectics (614–617 °С) with the participation of the Al27Ca3Cu7 and (Al,Cu)4Ca phases that are capable of spheroidization at high temperature annealing. The ingots of Ca-containing alloys do not require homogenization but have sufficient deformation plasticity at both hot and cold rolling. The structure of the previously unstudied quaternary Al–Cu–Mn–Ca phase diagram in the region of the aluminum corner has been also proposed, according to which it can contain 5 four-phase fields in the solid state with the participation of (Al), binary (Al2Cu, Al4Ca, Al6Mn) and ternary (Al8CaCu4, Al27Ca3Cu7, Al10CaMn2 and Al20Cu2Mn3) phases. Based on the obtained data, the composition Al–6 %Cu–2 %Mn–1 %Ca has been proposed as a basis for the development of a new heat-resistant alloy. It is shown that this alloy superior to industrial 2219 alloy in terms of heat resistance, especially after annealing at 400 °C, when the difference in hardness reaches 32 HV. The high heat resistance of the new wrought alloy originates from the formation of a specific microstructure consisting of fine Ca-containing eutectic inclusions and Al20Cu2Mn3 phase dispersoids with a size of about 100 nm which prevent recrystallization and allow maintaining the fine sub-grained structure.

Enhanced age hardening response of a Mg-Y alloy by Ca addition at an elevated temperature

The effect of Ca addition on the age hardening response and precipitation behavior of a Mg-7Y-0.5Zr (wt%) alloy during isothermal aging at 350 ℃ has been studied by hardness test and high-angle annular dark-field scanning transmission electron microscopy. The addition of 0.6 wt% Ca can effectively enhance the age hardening response of Mg-7Y-0.5Zr alloy at 350 ℃, and the enhanced hardness is mostly attributed to the uniform precipitation of a novel strengthening precipitate phase, designated βp. The βp phase forms as plates on {101̅0}α planes. It has a Cd45Sm11-type structure (space group F4̅3m, lattice parameter a = 2.24 nm) and a composition of Mg5Y0.8Ca0.2. Its orientation relationship with the α-Mg matrix phase is such that [1̅11]βp // [21̅1̅0]α and (110)βp // (0001)α. After prolonged aging at 350 ℃, the metastable phase βp can transform in-situ to the equilibrium phase β-Mg24Y5 with a cube-to-cube orientation relationship. The βp → β phase transformation is associated with the transition of constituent atomic clusters and the re-distribution of selected atoms within clusters.

Effect of Ca addition on microstructure and mechanical properties of Mg–3.8Al–1.1Sn alloys

Effect of Ca addition on microstructure and mechanical properties of Mg–3.8Al–1.1Sn alloys

Effects of Ca addition on microstructure, mechanical properties and corrosion behaviors of solution treated Mg-5Ga-xCa alloys

Effects of Ca addition on microstructure, mechanical properties and corrosion behaviors of solution treated Mg-5Ga-xCa (x = 0, 0.2, 0.5, 0.8 wt%) alloys are investigated. The Mg5Ga2 phase is almost dissolved into the matrix after solution treatment, while the residual phases mainly the Mg-Ga-Ca phase increases with the higher Ca content. The solution treated Mg-5Ga-0.2Ca alloy exhibits the highest corrosion resistance (with the average weight loss rate of 0.349 mg·cm−2·d−1 in Hank’s solution for 7 days) and the appropriate mechanical properties, with the ultimate tensile strength of 212 MPa and the elongation to rupture of 16.9%. Its high corrosion resistance can be mainly attributed to the protective effect of the Mg2Ca phase as a corrosion anode with low standard potential, the well-protected corrosion product film and the small grain size, while its good mechanical properties are due to the grain refinement and the solid solution strengthening of more Ga atoms. With a further increase in Ca content (≥0.5 wt%), although the grains are more refined, both the mechanical properties and corrosion resistance of the alloy decrease because of the residual phases in large quantities and low solution of Ga atoms.

Effect of Ca addition on near-infrared reflection of SrCuSi4O10

Abstract In this study, SrCuSi4O10 powders were synthesized by a complex polymerization method and the effect of Ca addition on the crystal structure and optical properties in the visible and near-infrared regions was examined. Crystalline SrCuSi4O10 was formed at 1,000 °C in air. From the X-ray diffraction measurements, the (002) and (004) reflections of SrCuSi4O10 shifted to higher angles, and the lattice parameter (a and c) decreased with the addition of Ca, suggesting that Ca was successfully introduced into SrCuSi4O10. However, the lattice constant of SrCuSi4O10 increased with further addition of Ca to 10 mol%. Optical measurements of SrCuSi4O10 identified three optical absorption bands in the visible light region, attributed to the d–d transition of Cu2+: namely 2B1g → 2B2g (540 nm), 2B1g → 2Eg (628 nm), and 2B1g → 2A1g (800 nm). The addition of Ca decreased the intensity of these absorptions. The –b* value, which indicates blueness, was estimated using the L*a*b* color system, and SrCuSi4O10 with 5 mol% Ca showed the highest value among the measured samples. On the other hand, the reflectance of SrCuSi4O10 in the near-infrared region increased significantly with the addition of Ca. These results indicate that Ca addition is effective in improving the blue coloration and near-infrared reflectivity of SrCuSi4O10.

Effect of Ca Addition on Inclusions of Welding Heat-Affected Zone in Pressure Vessel Steels

Pressure vessel steels are used in the manufacture of tanks for the storage of gases, chemical materials and oil. To meet the increasing production demands, high-wire-energy welding is widely used in the manufacture of pressure vessel steels. This means that the weldability of pressure vessel steels needs to be improved. Therefore, in order to reveal the microalloying effect of Ca in pressure vessel steel, this study took a commonly used pressure vessel steel as the research object, and three groups of experimental steels with different Ca mass fractions were prepared using vacuum metallurgy, controlled rolling and controlled cooling. Welding heat simulation technology was used to simulate the welding heat of experimental steel and the welding heat-affected zone (HAZ) was investigated. The inclusions of the welding HAZ in the experimental steels were observed by using a metallographic microscope and scanning electron microscope (SEM). The mechanism of intragranular acicular ferrite (IAF) nucleation induced by the inclusions containing Ca elements in the welding HAZ of pressure vessel steels was also discussed. The research results show that the addition of Ca increased the number density of effective inclusions in the welding HAZ of the experimental steel up to 535.60 pieces/mm2. The addition of the Ca element was beneficial for producing more pinning inclusions in the experimental steel welding HAZ under the experimental conditions, and the inclusions were mainly elliptical oxide complex inclusions of Ca-Si with a size of about 2 μm. Meanwhile, Al2O3 and MnS were precipitated. After the addition of Ca elements, Mn-poor regions appeared around the inclusions containing Ca in the welding HAZ. IAF nucleation was mainly induced by the local compositional change mechanism and supplemented by the stress–strain energy mechanism and inert interface energy mechanism. This study provides a valuable reference for optimizing the welding process of pressure vessel steels and is of great importance for understanding the IAF nucleation mechanism of Ca-containing inclusions in the welding HAZ of pressure vessel steels.

Effects of Ca addition on the microstructure and mechanical properties of Mg–Zn–Sn–Mn alloys

The effects of Ca addition on the microstructure and mechanical properties of Mg–Zn–Sn–Mn alloys were investigated in this study. The Mg–6Zn–4Sn–1Mn–xCa (x = 0, 0.2, 0.5, 1 and 2 wt%) alloys consist of the α-Mg, Mg2Sn, Mg7Zn3, MgZn, α-Mn, CaMgSn, MgZn2, Mg2Ca and Ca2Mg6Zn3 phases. With increasing Ca content, the eutectic phase and grains were refined, and the morphologies of the CaMgSn phases changed from point-like to needle-like, rod-like and lath-like. At room temperature, small amounts of Ca can improve properties owing to refinement strengthening. The two-stage aged Mg–6Zn–4Sn–1Mn–0.2Ca alloy has the best comprehensive properties at room temperature, with an ultimate tensile strength (UTS), yield strength (YS) and elongation of 407 MPa, 392 MPa and 6.2%, respectively. When the Ca content increased, the number of CaMgSn phases increased, and the morphologies coarsened. Further, it was a brittle phase, resulting in the deterioration of alloy properties. At high temperatures, a small amount of Ca can improve the high-temperature plasticity. The elongations of the as-extruded Mg–6Zn–4Sn–1Mn–0.2Ca alloy were 76.9% (150 °C) and 133.8% (200 °C). A high Ca concentration can significantly improve the high-temperature strengths because of the good thermal stability of the CaMgSn phases, the best UTS and YS are 160 MPa and 136 MPa, respectively, in as-extruded Mg–6Zn–4Sn–1Mn–2Ca alloy at 150 °C.

Effect of Ca Addition on Mechanical Properties and the Ignition Temperature of Cast WE43 alloys

Effect of Ca Addition on Mechanical Properties and the Ignition Temperature of Cast WE43 alloys

Effect of Ca addition on the microstructure and creep behaviour of AZ91 Mg alloy

The lower density and higher specific mechanical properties of the magnesium and its alloys are attracting the great attention of the automakers from the perspective of automobile fuel economy and reducing the environmental impact. The AZ91 magnesium alloy has excellent mechanical properties; however, its application is limited by its poor creep resistance. In the present study, the effect of Ca addition and squeeze casting on the microstructure and creep behaviour of AZ91 Mg alloy has been investigated. Tensile creep test is conducted at temperatures of 150 and 175 °C under 50 MPa stress. The study shows an increase in creep resistance with Ca addition. Microstructural investigations with scanning electron microscopy confirm that the precipitation of thermally stable Al2Ca phase with skeleton morphology leads to increased creep resistance.

Effect of Ca Addition on the Oxidation Resistance of Ni–Al Alloy

Effect of Ca Addition on the Oxidation Resistance of Ni–Al Alloy

Influence of Ca addition on microstructural characteristics and mechanical properties of Mg–5Bi–3Al alloy extruded at extremely high speed

In this study, the effects of Ca addition on the microstructural characteristics and mechanical properties of a Mg–Bi–Al alloy extruded at high speed were investigated by analyzing extruded Mg–5Bi–3Al (BA53) and Mg–5Bi–3Al–0.5Ca (BAX530) alloys fabricated at a speed of 70 m/min. The homogenized BA53 billet contained fine and coarse Mg3Bi2 particles, whereas the homogenized BAX530 billet contained only coarse Mg2CaBi2 particles. Both alloys exhibited fully recrystallized microstructures and similar grain sizes upon extrusion at the high speed. Ca-induced texture weakening did not occur in the extruded BA53 alloy because the added Ca was completely consumed during the formation of Mg2CaBi2 particles. Abundant fine Mg3Bi2 particles were uniformly distributed throughout the extruded BA53 alloy, whereas the extruded BAX530 alloy contained coarse Mg2CaBi2 particles. The addition of Ca to the BA53 alloy decreased the tensile strength by ∼10%, primarily due to weakened particle hardening. Under tension, an increased number of {10–11} contraction and {10–11}-{10–12} double twins were formed and a larger number of twin variants were activated in the extruded BAX530 alloy than in its Ca-free counterpart; consequently, Ca addition enhanced the tensile elongation of the extruded alloy by ∼21% via suppressing the local strain concentration. Thus, the addition of a small amount of Ca can enhance the tensile ductility of high-speed-extruded Mg–Bi-based alloys with high Bi contents without altering the alloy texture.

Effect of Ca addition on the mechanical properties and thermal conductivity of Mg-2Ga alloy

The Ca concentration dependence of microstructure, mechanical properties and thermal conductivity of Mg-2Ga-xCa (x = 0, 0.2, 0.4 and 0.8, in wt.%) alloys has been investigated at room temperature. As the Ca content increases, both the average grain size and the volume fraction of dynamically recrystallised grains decrease in the as-extruded alloys, leading to an increase in yield strength. However, the increase in the number and the size of second phase particles associated with the higher Ca content brings about the reduced plasticity. In addition, a minor Ca addition (0.2% and 0.4%) to the Mg-2Ga alloy has no significant effect on the thermal conductivity, but the 0.8%Ca addition can improve the thermal conductivity of the as-cast and as-extruded Mg-2Ga alloys significantly, which is mainly related to the reduction of solute Ga atoms in α-Mg. Meanwhile, the as-extruded alloy exhibits the higher thermal conductivity than the corresponding as-cast alloy. The as-extruded Mg-2Ga-0.8Ca alloy exhibits the tensile yield strength of 244 MPa and the thermal conductivity of 135.5 W·m-1·K-1. It is desirable to design Mg alloys with high strength and high thermal conductivity by selecting proper alloying elements for the formation of the precipitates other than dissolving in the Mg solution.

Biodegradable properties of AZ31-0.5Ca magnesium alloy

ABSTRACT In this work, the effect of Ca addition on the microstructure, mechanical properties, electrochemical corrosion and biocompatibility of AZ31 Mg alloy was investigated. Scanning electron microscopy and electron probe microanalyzer were used to analyse microstructural characteristics of both alloys. Open circuit potential , potentiodynamic polarisation and electrochemical impedance spectroscopy techniques were carried out in Ringer lactate solution at 37 ± 1°C to determine the mechanism of corrosion and rate of deterioration of AZ31 and AZ31-0.5Ca. The results revealed that addition of Ca significantly enhanced the corrosion resistance of AZ31 (20.21 mpy and 10.08 mpy for AZ31 and AZ31-0.5Ca, respectively), which was attributed to the presence of second phase particles. the cell viability and biocompatibility of the both alloys were determined by performing the cytotoxicity test after 24 h, 48 h and 72 h incubation in L929 and MC3T3-E1 cell extract. Both the alloys demonstrated adequate cell viability and biocompatibility.

Effects of Ca addition on microstructure, electrochemical behavior and magnesium-air battery performance of Mg-2Zn-xCa alloys

• Effect of Ca on the properties of second phases in Mg-Zn-Ca alloys was studied. • The optimal alloy exhibits beneficial corrosion resistance and discharge properties. • Discharge sequence of precipitated second phases was investigated. In this research, the micro-morphologies, electrochemical behaviors and battery discharge performances of the Mg-2Zn- x Ca alloys as potential anode materials were investigated. The micro-morphology results showed that for the alloy with low Ca content ( x = 0.1 and 0.2), only the Ca 2 Mg 6 Zn 3 phase was observed to precipitate in a punctate form within the crystal. As the Ca content rose, the amount of the punctate Ca 2 Mg 6 Zn 3 increased while the strip-shaped Ca 2 Mg 6 Zn 3 phase precipitated at the grain boundary was also observed. When the Ca content reached 0.5 wt% and higher, the second phases were observed to be both Mg 2 Ca and Ca 2 Mg 6 Zn 3 phase which precipitated at the grain boundary and the morphology of second phases gradually changes into a continuous network. Among the four tested alloys, the Mg-2Zn-0.2Ca sample delivered the best electrochemical activity with more negative corrosion potential and larger corrosion resistance in electrochemical experiments. Battery performance tests showed that the Mg-2Zn-0.2Ca anode exhibited an improved specific capacity of 1344.1 mAh g −1 and high anodic efficiency of 61.0% at 10 mA cm −2 . The discharge order of the precipitated phase has been derived as follows: Mg 2 Ca > Mg > Ca 2 Mg 6 Zn 3 .

Effect of Ca Addition on the Mechanical Properties and Thermal Conductivity of Mg-2ga Alloy

Effect of Ca Addition on the Mechanical Properties and Thermal Conductivity of Mg-2ga Alloy

Effect of Ca addition on the microstructure, mechanical properties and corrosion rate of degradable Zn-1Mg alloys

The microstructural evolution, mechanical properties and degradation behaviors of as-cast Zn-1Mg alloy and Zn-1Mg-xCa (x = 0.3 wt% and 0.5 wt%) alloys were investigated. The microstructural evolution showed that adding Ca element effectively refined α-Zn from coarse dendrites to equiaxed grains, and the average size gradually decreased with the increasing contents of Ca in Zn-1Mg alloy. Moreover, the morphology of eutectic Mg2Zn11 phases changed from lamellar shape to honeycomb, and the amount of precipitated CaZn13 phases distributed in grain boundaries increased, when the 0.3 wt% and 0.5 wt.%Ca were introduced into Zn-1Mg alloy melt. Tensile test results revealed that the yield strength (YS), ultimate tensile strength (UTS) and elongation (El) of Zn-1Mg-0.5Ca alloy (118.7 MPa, 169.3 MPa, 3.42% for YS, UTS and El, respectively) is improved by 40.5%, 41.4% and 189.8%, respectively, compared with Zn-1Mg alloy (84.5 MPa, 119.7 MPa, 1.18% for YS, UTS and El, respectively). The method of electrochemical polarization testing was employed to measure the corrosion rate of Zn-1Mg-xCa alloys in Hanks simulated body fluid. The result exhibited that the corrosion rate of Zn-1Mg alloy without and with 0.3 wt% and 0.5 wt%Ca addition gradually increased, which was 0.125 mm.a−1, 0.176 mm.a−1 and 0.190 mm.a−1, respectively. In addition, the corrosion rates of Zn-1Mg-xCa alloys immersed in Hank’s solution holding for one month were summarized as: as-cast Zn-1Mg-0.5Ca alloy (0.182 mm.a−1)> as-cast Zn-1Mg-0.3Ca alloy (0.168 mm.a−1)> as-cast Zn-1Mg alloy (0.134 mm.a−1). The investigation of mechanical properties and corrosion rate demonstrated that newly developed Zn-1Mg alloys with Ca addition can be thought of a hopeful biodegradable medical material.

Effect of Ca Addition on Corrosion Behavior of Wrought AM60 Magnesium Alloy in Alkaline Solutions

Magnesium (Mg) alloys possess the lowest density among structural materials, and their application in the automotive and aircraft industries might enhance fuel efficiency. The mechanical properties can be improved by the addition of alloying elements. However, since Mg and its alloys are very susceptible to corrosion degradation, it is important to study the effect of these elements on the alloys’ corrosion behavior. In this study, 1 wt% of calcium (Ca) was added to wrought AM60 Mg alloy, and the electrochemical corrosion behavior of the alloys in alkaline solutions with and without Cl− ions was compared. The corrosion behavior was investigated by means of immersion tests, gravimetric measurements and potentiodynamic polarization (PDP); the characteristics of the oxide layer were studied by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The addition of Ca resulted in precipitation of the ternary aluminum-rich (Mg-Al)2Ca phase. Scanning Kelvin probe force microscope (SKPFM) identified that this phase has a cathodic behavior relative to the α-Mg matrix; hence it can serve as additional sites for initiation of pitting corrosion. As a result, the corrosion resistance of wrought AM60 alloy with 1 wt% Ca addition deteriorated in a NaCl solution. However, in the absence of Cl− ions, alloying with Ca improves the corrosion resistance of wrought AM60 alloy due to the stabilization of the corrosion products layer. The effect of long-period immersion time on the corrosion behavior and alloy oxidation is discussed.

Linear Friction Welding of an AZ91 Magnesium Alloy and the Effect of Ca Additions on the Weld Characteristics.

Solid-state welding offers distinct advantages for joining reactive materials, such as magnesium (Mg) and its alloys. This study investigates the effect of linear friction welding (LFW) on the microstructure and mechanical properties of cast AZ91 (Mg–9Al–1Zn) and AZ91–2Ca alloys, which (to the best knowledge of the authors) has not been reported in the literature. Using the same set of LFW process parameters, similar alloy joints—namely, AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca—were manufactured and found to exhibit integral bonding at the interface without defects, such as porosity, inclusions, and/or cracking. Microstructural examination of the AZ91/AZ91 joint revealed dissolution of the Al-rich second phase in the weld zone, while the Mn containing phases remained and were refined. In the AZ91–2Ca/AZ91–2Ca joint, the weld zone retained Ca- and Mn-rich phases, which were also refined due to the LFW process. In both joint types, extensive recrystallization occurred during LFW, as evidenced by the refinement of the grains from ~1000 µm in the base materials to roughly 2–6 µm in the weld zone. These microstructural changes in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints increased the hardness in the weld zone by 32%. The use of digital image correlation for strain mapping along the sample gage length during tensile testing revealed that the local strains were about 50% lower in the weld zone relative to the AZ91 and AZ91–2Ca base materials. This points to the higher strength of the weld zone in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints due to the fine grain size, second phase refinement, and strong basal texture. Final fracture during tensile loading of both joints occurred in the base materials.

Effect of Ca addition on the microstructure and mechanical properties of heat-treated Mg-6.0Zn-1.2Y-0.7Zr alloy

In this study, the effects of Ca addition on the microstructure, thermal properties, and mechanical properties of a Mg-6.0Zn-1.2Y-0.7Zr (ZWK611) alloy at room temperature and 150 °C were investigated. With an increase in the Ca content, the ignition resistance of the ZWK611 alloy improved and the grains became finer. The as-cast ZWK611 alloy consisted mainly of the dendritic α-Mg matrix and I-phase (Mg3Zn6Y) at the grain boundaries. On the other hand, the τ- (Ca2Mg6Zn3) and I-phases were formed in the Ca-added ZWK611 alloy. The fraction of the τ-phase increased with an increase in the Ca content. After the solid-solution treatment, these phases remained partially at the grain boundaries of the Ca-added ZWK611 alloys and an additional W-phase (Mg3Zn3Y) was observed. The phases remaining at the grain boundaries restricted the grain growth through the grain boundary pinning effect. The aging treatment resulted in the formation of MgZn' precipitates in the α-Mg matrix of the alloys. These precipitates were more uniformly distributed in the Ca-added alloys than in the alloys without Ca. Thus, the heat treatment-induced precipitation improved the tensile and creep properties of the T6-treated alloys. The T6-treated ZWK611+0.7Ca alloy exhibited the best mechanical properties at room temperature and 150 °C among all the tested alloys.