Influence Of Ca Addition Research Articles

Influence of Ca addition on the dynamic and static recrystallization behavior of direct extruded flat profiles of Mg-Y-Zn alloy

This paper investigates the influence of addition of Ca in a Y-Zn-containing magnesium alloy on the dynamic and static recrystallization behaviors and reveals the formation mechanism of the quadrupole texture during thermomechanical processing. Direct extrusion of flat bands has been conducted at various process conditions to study the difference between the two alloys WZ10 and WZX100 in terms of microstructure and texture development. It can be shown that, Ca addition promotes the DRX of WZ10 alloy. During additional heat treatment, the absence of Y segregation at the grain boundaries and the associated lack of solute drag to the boundary mobility leads to a pronounced grain growth during SRX in WZX100 alloy. Furthermore, it is shown that the addition of Ca to Y-Zn is not beneficial in terms of formability. It is demonstrated that alloying elements can have different effects depending on the recrystallization mechanisms. Partially recrystallized microstructure is a prerequisite at the as-extruded status to form the quadrupole texture and during subsequent annealing, which stands for high formability.

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 Content on Hot Tearing Susceptibility of Mg-4Zn-xCa-0.3Zr (x = 0.5, 1, 1.5, 2) Alloys

Mg–Zn–Ca alloy has a good development prospect in biomedical alloy. However, its development is restricted by large hot tearing susceptibility. Herein, the influence of Ca addition on the hot tearing susceptibility (HTS) of Mg-4Zn-xCa-0.3Zr (0.5, 1, 1.5, and 2 wt%) alloys has been studied by using thermal analysis and numerical simulation software, Procast. The “Clyne–Davies” hot tearing prediction model was improved, and Cracking Susceptibility Coefficient (CSC) was recalculated to highlight the physical significance of the model. The hot tearing zone was observed via optical microscopy and scanning electron microscopy, and the phase composition was analyzed with X-ray diffraction. The results of numerical simulations suggest that the Hot Tearing Indicator (HTI) tended to decrease with increase in Ca addition. However, the experimental results reveal that with the increase in Ca addition, the hot tearing susceptibility of the alloys first decreased with Ca addition up to 1.5 wt% and then displayed a slight increase with the addition up to 2.0 wt%. The SEM images and experimental results reveal that the thickness and ability to resist solidification shrinkage stress of the liquid membrane, quantity of the second phases, and feeding ability were all enhanced with the increase in Ca addition, thereby reducing the HTS of Mg-4Zn-XCa-0.3Zr alloys. When the Ca addition reached 2.0 wt%, the brittle calcium-containing phase forms at the grain boundary, which reduces the high-temperature strength of the matrix and the ability to resist the solidification shrinkage stress of the alloy, resulting in an increase in HTS. Therefore, when the Ca addition was 2.0 wt%, the simulation results were different from the experimental results.

Influence of Ca addition on microstructure, mechanical properties and corrosion behavior of Mg-2Zn alloy

The microstructure, mechanical properties and corrosion behaviors of as-cast ternary Mg-2Zn-xCa (x=0, 0.2, 0.4, 0.8) alloys have been investigated in this study. Results indicate that the microstructure of Mg-Zn-Ca alloys can be significantly refined with increasing Ca concentration. Moreover, the alloys with different contents of Ca exhibit the different phases formation behaviors, i.e. α-Mg + Ca2Mg6Zn3 phases for Mg-2Zn-0.2Ca and Mg-2Zn-0.4Ca alloys, and α-Mg + Ca2Mg6Zn3 + Mg2Ca phases for Mg-2Zn-0.8Ca alloy, respectively. Among all the alloys, the maximum ultimate tensile strength and elongation (161 MPa and 9.1%) can be attained for the Mg-2Zn-0.2Ca alloy. Corrosion tests in Hanks’ balanced salt solution indicated that Ca addition is detrimental to corrosion resistance of Mg-2Zn alloy. The relationship between as-cast microstructure and properties for different Ca-containing alloys is also discussed in detail.

Does an earthworm species acclimatize and/or adapt to soil calcium conditions? The consequences of soil nitrogen mineralization in forest soil

AbstractCalcium (Ca)‐rich food can increase feeding of Lumbricidae. Earthworms can be genetically differentiated at a small spatial scale and acclimatize to the local environment during growth. Soil feeding and subsequent cast production by earthworms affects soil N mineralization. Here, we hypothesized that soil feeding and subsequent cast production by Lumbricidae species increases with high soil Ca content and that this increase is stronger in worms from high‐Ca soil. We also hypothesized that changes in the soil feeding of Lumbricidae species along with the Ca content affects the soil N mineralization via changes in the cast production. Using a geophageous earthworm species (Eisenia japonica) originated from two different Ca environments (calcareous soil and sedimentary soil), we investigated cast production and soil N mineralization in three soils (sedimentary soil, sedimentary soil with Ca addition, and calcareous soil). The soil feeding of E. japonica from both origins did not always increase despite the high soil Ca content. We suggest that both the Ca content and other soil conditions (e.g., soil C:N) might be major factors in increasing soil feeding by E. japonica. Furthermore, the influence of Ca addition on cast production varied according to the earthworm origin. As expected, these differences in cast production are linked to soil N mineralization (especially nitrification). In summary, our study suggests that the acclimatization and/or adaptation of Lumbricidae species to local environmental factors not only soil Ca content explains spatially heterogeneous soil N mineralization in forest soil.

Effect of calcium addition on microstructure, casting fluidity and mechanical properties of Mg-Zn-Ce-Zr magnesium alloy

The influence of Ca addition on the as-cast microstructure, casting fluidity and mechanical properties of the Mg-4.2Zn-1.7Ce-0.5Zr (wt.%) alloy was investigated. The results showed that the as-cast alloys consisted of α-Mg matrix, Ca-contained T-phase and Mg51Zn20 phase. Addition of 0.2 wt.%–0.6 wt.% Ca led to effective grain refinement and enhanced the fluidity of the alloys. When the content of Ca was 0.2 wt.%, the alloy exhibited the finest grain size of 35.9 μm, and the filling length was increased by approximately 55.4% compared with the quaternary alloy. The improvement of the fluidity was attributed to the grain refinement, less energy dissipation and the oxidation resistance of Ce and Ca. With an increase in Ca content, the yield strength increased gradually, whereas the ultimate tensile strength and elongation showed a decreasing tendency. Moreover, the fracture surface mode was quasi-cleavage fracture.

Influence of Ca addition on microstructural evolution and mechanical properties of near-eutectic Mg–Li alloys by copper-mold suction casting

The influence of small amount of Ca addition on the microstructures and mechanical properties of three near-eutectic Mg-x Li (x = 6.8, 7.5, 8.4 wt. %) binary alloys under rapid solidification condition by using Copper-mould Suction Casting technique were investigated. The resultant microstructures were very distinct from those by conventional gravity casting technique in the morphology, grain size and the volume fraction of α-Mg phase. Mechanical properties of the Ca-modified Mg-x Li binary alloys were significantly enhanced. More interestingly, a eutectic growth mode transition from their regular divorced eutectic growth to the regular coupled eutectic structure was induced in Mg-8.4Li alloy via Ca addition. The eutectic transition mechanisms in three Mg-x Li alloys by Ca addition were discussed in terms of the freezing rate, Mg2Ca particle segregation, the relative volume fraction of α-Mg phase.

Effects of Ca on the formation of LPSO phase and mechanical properties of Mg-Zn-Y-Mn alloy

The influence of Ca addition on the microstructure and mechanical properties of Mg94Zn2.5Y2.5Mn1 alloy were investigated. Results showed that Ca induced the formation of long-period stacking ordered (LPSO) structure while discouraged that of Mg3Zn3Y2 eutectic structure. With Ca addition, the microstructure were refined, and the mechanical properties were enhanced.

Influence of Particle Size and Ca Addition on the Magnetic Performance and Microstructure of MnZn Ferrite

In this work, the influence of Ca addition on the power loss of MnZn ferrites was investigated. Mn–Zn ferrites were prepared by conventional oxide ceramic process from calcined powders of different particle sizes in equilibrium sintering atmosphere. It has been found that the optimal amount of Ca addition varies for the Mn–Zn ferrites synthesized by using powders of different particle size.

Microstructural evolution during creep of Ca-containing AZ91

The influence of Ca addition on the microstructure and creep properties of AZ91 has been investigated in this work. Creep tests in compression in the temperature range between 150 and 200 °C and stresses between 70 and 200 MPa show an increase in creep resistance with an increasing Ca addition. Microstructural investigations with scanning electron microscopy show that with increasing amount of Ca the intermetallic phase gets more skeletal and finer and the creep resistance increases. Thermal treatment does not significantly influence creep properties of an AZ91 alloy with 5 wt.% Ca addition. In contrast to this, pre-deformation of this alloy leads to higher creep rates compared to as-cast samples. This can also be understood by microstructural investigations, as deformation leads to fracture of the skeletal intermetallic phase, which is surrounding the α-magnesium particles.