CaMgSn Phase Research Articles

Effect of extrusion speeds on the microstructure, texture and mechanical properties of high-speed extrudable Mg[sbnd]Zn[sbnd]Sn[sbnd]Mn[sbnd]Ca alloy

A new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt.%) (named as ZTMX3100) alloy ingot with good extrudability was prepared by semi-continuous casting. Two-stage homogenization treatment and hot extrusion were performed on the ingot. The effects of extrusion speeds (0.2–10 mm/s) on the extrudability, microstructure and mechanical properties of the alloy were investigated. The excellent extrudability of the alloy is attributed to the high incipient melting temperature of 572 °C resulting from the formation of thermally stable phase CaMgSn. CaMgSn phases distribute along the extrusion direction at each extrusion speed. The average grain size increases gradually and distribution uniformity of grain size firstly increases and then decreases. The as-extruded alloys exhibit textures with (0001) basal planes parallel to extrusion direction. Besides, the alloy exhibits a <101¯0> or <101¯0> − <112¯0> fiber texture depending on extrusion speed. The alloy extruded at 0.2 mm/s presents the highest mechanical property, which is attributed to the fine grain structure, strengthening effect from second phase particles, and weak basal texture. The alloy extruded at high speed of 10 mm/s (die-exit speed 18 m/min) still maintains a relatively high strength and elongation, which is mainly due to the combined effect of moderate alloying content and thermally stable phase CaMgSn.

Effect of Zn and Ca Addition on Microstructure and Strength at Room Temperature of As-Cast and As-Extruded Mg-Sn Alloys.

In this study, the effect of Zn and Ca addition on microstructure and strength at room temperature of Mg-Sn alloys was investigated by comparison of Mg-6Sn, Mg-6Sn-2Zn, and Mg-6Sn-2Zn-1Ca alloys in as-cast and as-extruded states. In the as-cast samples, α-Mg and Mg2Sn phases were the main phases of Mg-6Sn and Mg-6Sn-2Zn alloys, while the CaMgSn phase was formed in Mg-6Sn-2Zn-1Ca alloy due to the addition of the Ca element. Mg2Sn phase dissolved into the matrix during homogenization while CaMgSn phase remained. Incomplete dynamic recrystallization (DRX) took place in these alloys during hot extrusion. Fine Mg2Sn precipitates were observed in α-Mg matrix of as-extruded samples. Zn showed little influence on microstructure, whereas Ca reduced the volume fraction of un-DRXed grains and increased the size of DRXed grains. As-extruded Mg-Sn alloys exhibited typical fiber texture. The strength at room temperature of Mg-Sn alloys improved significantly after hot extrusion. The addition of Zn element was beneficial to the strength at room temperature of the Mg-6Sn alloy, while the further addition of Ca element was harmful to the strength. Among these alloys, the Mg-6Sn-2Zn alloy exhibited the best strength at room temperature in both as-cast and as-extruded states.

Enhanced age-hardening response and compression property of a Mg-7Sn-1Ca-1Ag (wt.%) alloy by extrusion combined with aging treatment

The age-hardening response and compression property of a Mg-7Sn-1Ca-1Ag (wt.%) alloy are improved by extrusion combined with aging treatment (abbreviated as extruded-aged). The corresponding microstructure evolution was investigated and discussed in detail. The results show that the average grain size of alloy was refined obviously from ∼54.6 μm to ∼3.2 μm by extrusion at 320 °C and the refinement of CaMgSn phase is also exhibited. Extrusion process promotes the precipitation of Mg2Sn and Mg54Ag17 phase and more precipitates of Mg2Sn phase exists in the extruded-aged alloy. As a result, age-hardening response and compressive strength are significantly enhanced in the extruded-aged Mg-7Sn-1Ca-1Ag alloy. The peak-aged hardness and ultimate compressive strength (UCS) of extruded-aged Mg-7Sn-1Ca-1Ag alloy are 95.2 HV and 482 MPa, respectively, both of which are obviously higher than that of as-aged and as-extruded alloys. This is mainly attributed to the grain refinement, formation of Mg54Ag17 phase and the increased content of finer Mg2Sn precipitates. Moreover, it was found that an obvious yield behavior occurs in compressive engineering stress versus strain of extruded and extruded-aged alloys, which is mainly attributed to the basal texture caused by extrusion and high value of Schmid factor, leading to the easy formation of {10–12} twinning in the extruded-aged alloy during compression along the extrusion direction.

Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting.

In this paper, a new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt %) alloy ingot with a diameter of 130 mm and a length of 4800 mm was fabricated by semicontinuous casting. The microstructure and mechanical properties at different areas of the ingot were investigated. The microstructure and mechanical properties of the alloy under different one-step and two-step homogenization conditions were studied. For the as-cast alloy, the average grain size and the second phase size decrease from the center to the surface of the ingot, while the area fraction of the second phase increases gradually. At one-half of the radius of the ingot, the alloy presents the optimum comprehensive mechanical properties along the axial direction, which is attributed to the combined effect of relatively small grain size, low second-phase fraction, and uniform microstructure. For the as-homogenized alloy, the optimum two-step homogenization process parameters were determined as 340 °C × 10 h + 520 °C × 16 h. After the optimum homogenization, the proper size and morphology of CaMgSn phase are conducive to improve the microstructure uniformity and the mechanical properties of the alloy. Besides, the yield strength of the alloy is reduced by 20.7% and the elongation is increased by 56.3%, which is more favorable for the subsequent hot deformation processing.

Effects of Sn addition on the microstructure and tensile properties of AX55 alloys

The microstructures and tensile properties at both room and elevated temperatures for both the as-cast and as-aged Mg-5Al-5Ca (AX55) alloy with 0–2 wt% Sn addition were studied. The results indicate that the α-Mg dendrite is gradually refined and the interdendritic Al2Ca and Mg2Ca intermetallics become more connected with Sn addition. The as-cast AX55-1Sn alloy shows optimal ultimate tensile strength (UTS) at testing temperature from 25 to 225 °C. After T61 and T62 heat treatment, the eutectic-lamellar microstructure of the as-cast alloys tends to be spheroidized and distributed uniformly along the grain boundaries. While the alloys with higher Sn content show higher density of granulated and needle-shaped Al2Ca phases precipitated into α-Mg matrix, which results in the increase of UTS, yield strength (YS), elongation and microhardness with Sn addition. The morphology of CaMgSn phase can be improved by T62 treatment, which makes as-aged AX55-2.0Sn alloy exhibit a smaller decrease rate of the UTS at temperature up to 225 °C. The heat resistance of different heat-resistant magnesium alloys were compared and discussed by using the decrease rate of the UTS.

Effect of Sn addition on hot tearing susceptibility of AXJ530 alloy

The effects of different Sn additions (0, 0.5, 1.0, and 2.0 wt%) on hot tearing susceptibility (HTS) of AXJ530 alloy were studied using ‘T-shaped’ hot tearing mold at a pouring temperature of 700 °C and a mold temperature of 200 °C and paraffin permeation method. The dendrite coherency temperature was obtained by means of differential thermal analysis (DTA), and phases evolution, microstructures and morphology of the crack zone of AXJ530-xSn alloys were also investigated by using x-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The experimental results show that the HTS of AXJ530-xSn alloys increases with Sn additions up to 1.0 wt%, and then exhibits a slight decrease with further Sn additions up to 2.0 wt%. The Sn additions into AXJ530 alloy can first form CaMgSn phase with high melting point, reduce amount of α-Mg+(Mg,Al)2Ca eutectic phase, increase the dendrite coherency temperature, decrease the thickness of liquid film and the feeding ability at the end of solidification, resulting in the rise of the HTS. However, the improvement in hot tearing resistance for AXJ530-2.0Sn alloy can be attributed to the grain refinement, lower dendrite coherency temperature and formation of the Mg17Al12 phase with a low melting point to feed more readily at the end of solidification, which improves the state of dendrite and the feeding channel.

Microstructure, Tensile Properties, and Corrosion Behavior of Die-Cast Mg-7Al-1Ca-xSn Alloys

The microstructure, tensile properties, and corrosion behavior of die-cast Mg-7Al-1Ca-xSn (x = 0, 0.5, 1.0, and 2.0 wt.%) alloys were studied using OM, SEM/EDS, tensile test, weight loss test, and electrochemical test. The experimental results showed that Sn addition effectively refined grains and intermetallic phases and increased the amount of intermetallic phases. Meanwhile, Sn addition to the alloys suppressed the formation of the (Mg,Al)2Ca phase and resulted in the formation of the ternary CaMgSn phase and the binary Mg2Sn phase. The Mg-7Al-1Ca-0.5Sn alloy exhibited best tensile properties at room temperature, while Mg-7Al-1Ca-1.0Sn alloy exhibited best tensile properties at elevated temperature. The corrosion resistance of studied alloys was improved by the Sn addition, and the Mg-7Al-1Ca-0.5Sn alloy presented the best corrosion resistance.

Microstructure and mechanical properties of Mg-3.0Zn-1.0Sn-0.3Mn-0.3Ca alloy extruded at different temperatures

A new type of wrought magnesium alloy Mg-3.0Zn-1.0Sn-0.3Mn-0.3Ca (ZTMX3100) was developed in this work. The effects of extrusion temperature (200–400 °C) on grain structure, second phase particle, texture, and mechanical properties of the alloy were systematically investigated by combining microstructure observations and mechanical properties tests. The results indicated that dynamic recrystallization occurs at 200–400 °C in the alloy. As the extrusion temperature increases, the average grain size increases gradually from 2.6 μm to 17.8 μm due to different degrees of grain growth, the continuous CaMgSn phase bands are gradually broken into discontinuous chain-like or dot-like structures, and the grains and CaMgSn phases distribute more uniformly. The as-extruded alloys exhibit a typical extruding texture with (0001) basal planes parallel to the extrusion direction. The bar extruded at 300 °C presents the optimum comprehensive mechanical properties, which is attributed to the combined effect of relatively small grain size, uniformly distributed discontinuous particles, and weak basal texture. Finally, the quantitative relationship between grain size and Zener-Hollomon parameter and the quantitative relationship between the yield strength of the alloy and extrusion temperature were obtained.

Effects of Ca, Ag addition on the microstructure and age-hardening behavior of a Mg-7Sn (wt%) alloy

The microstructure and age-hardening behaviors of Mg-7Sn, Mg-7Sn-1Ca and Mg-7Sn-1Ca-1Ag alloys have been investigated in this study. The results show that the combined addition of Ca and Ag in Mg-Sn alloy has a positive effect on grains refinement from 113.5µm of Mg-7Sn alloy to 54.3µm of Mg-7Sn-1Ca-1Ag alloy. Meanwhile, the size of CaMgSn phase is refined due to suppressing the formation and growth of CaMgSn phase by Ag element. The average length of CaMgSn phase decreases from 27.2 to 14.9µm. Compared with Mg-7Sn and Mg-7Sn-1Ca alloys, Mg-7Sn-1Ca-1Ag alloy exhibits the highest age-hardening response. The peak-aged hardness value increases from 61.1 HV to 80.4 HV by ageing treatment at 200℃ and the incubation period of age-hardening response also shortens from 80h to 20h with Ag addition. It is attributed to the effective promotion of dispersive precipitation and the volume fraction increasement of Mg2Sn precipitates in Mg-7Sn-1Ca-1Ag alloy, which can lead to a strong precipitation strengthening effect in α-Mg matrix.

Effect of tin on the microstructure and impression creep behavior of MRI153 magnesium alloy

The effect of tin on the microstructure and creep behavior of as cast magnesium MRI153 alloy was investigated in the present study. Creep behavior of the alloys were studied using impression creep test under shear modulus normalized stress ranging from 0.025 to 0.04 at temperatures of 152–217°C. Results showed that adding tin to MRI153 alloy reduces the amount of Al2Ca via forming CaMgSn phase, whereas the continuity and value of Mg17Al12 phase are increased. Solubility of calcium in Mg17Al12 phase is also reduced in the presence of tin. It was shown that adding tin to MRI153 alloy decreases the alloy creep strength, which can be attributed to the reduced value of Al2Ca phase and formation of CaMgSn phase instead as well as reduced thermal stability of Mg17Al12 phase and its increased value and continuity. By calculating creep activation energy and stress exponent, it was shown that although climb-controlled dislocation creep is the dominant mechanism in the creep of these alloys, the creep activation energy is decreased with increasing the amount of tin.

Hot Forging of Cast Magnesium Alloy TX31 Using Semi-Closed Die and its Finite Element Simulation

Magnesium alloys based on Mg-Sn-Ca system have shown improved corrosion and creep properties. In this type of alloys,Sn forms a solid solution with Mg that improves the corrosion resistance while Ca forms thermally stable intermetallic phases in the matrix enhancing the creep resistance. The Sn to Ca ratio is an important variable in deciding the type of intermetallic phases that form in the microstructure.In Mg-3Sn-1Ca alloy (TX31), a single intermetallic phase CaMgSnforms, which is responsible for its improved creep strength.With a view to evaluate its forgeability,isothermal forging experiments of TX31 were conducted on a hydraulic press in the temperature range of 350 °C to 500 °C and at speeds of 0.01 mm s-1to 10 mm s-1 using a semi-closed die. Finite-element (FE) simulation of the forging process was also conducted using the software DEFORM 2D to obtain the local variations of strain and strain rate. The effectivestrain values are below2.4 in the forged components and the forging loads predicted using FE simulation correlated well with the experimental data for all the forging conditions. The microstructures of the forgings show that CaMgSn phase is well distributed in the matrix which exhibited dynamically recrystallized microstructure as predicted by the processing map.

The role of Ca on the microstructure and corrosion behavior of Mg–8Sn–1Al–1Zn–Ca alloys

The influence of Ca (1–3 wt.%) content on the microstructure and corrosion behavior of Mg–8Sn–1Al–1Zn–Ca alloys have been investigated by OM, XRD, SEM and potentio-dynamic measurements and salt spray tester. The average grain size of studied alloys decreased from 79μm to 52μm with increasing Ca content. The morphology, number and size of second phase particles are found to be the Ca content dependence. After Ca addition, the new phases of CaMgSn and Mg2Ca can be found, with the CaMgSn phase presenting neddle-like or particle-like shape. And both of the Mg2Ca and the CaMgSn phases showed severe segregation as the Ca content exceed 2wt.%. The corrosion resistance of the studied alloys increased firstly and then decreased as the Ca content increased. The Mg–8Sn–1Al–1Zn–1Ca alloy exhibited the best corrosion resistance behavior with the corrosion rate of 8.1mm/a.

Microstructure and mechanical properties of as-cast Mg–Sn–Ca alloys and effect of alloying elements

The effect of Sn, Ca, Al, Si and Zn addition on the compressive strength of cast Mg–Sn–Ca (TX) alloys was studied in the temperature range of 25–250 °C and correlated with the microstructure. The Sn to Ca mass ratio up to 2.5 contributes to the formation of Mg2Ca phase at the grain boundaries and CaMgSn in the matrix, while a ratio of 3 gives only CaMgSn phase mostly in the matrix. While the compressive strength decreases with the increase in temperature, for Sn/Ca up to 2.5, a plateau occurs in 100–175 °C, which is attributed to the strengthening by Mg2Ca. However, for ratio of 3, the strength is lower and decreases more gradually. Mg–3Sn–2Ca (TX32) has the highest strength and the addition of 0.4% Al increases its strength but simultaneous addition of Si lowers the strength. Likewise, the addition of Zn improves its strength but simultaneous addition of Al slightly decreases the strength. The results are correlated with the types of intermetallic phases that form in various alloys.

Effects of Sn Addition on as-Cast Microstructure and Mechanical Properties of Mg-3.8Zn-2.2Ca Magnesium Alloy

Abstract The as-cast microstructure, tensile and creep properties of Mg-3.8Zn-2.2Ca-xSn (x=0, 0.5, 1, 2, wt%) alloys were investigated. The results indicate that the CaMgSn phase is formed in the Sn-containing alloys, and an increase in Sn content from 0.46 wt% to 1.88 wt% causes the amount of the CaMgSn phase to increase. Simultaneously, the morphology of the Ca2Mg6Zn3 phase changes from the initial continuous and/or quasi-continuous net to the quasi-continuous and/or disconnected shapes. Furthermore, the grains of the Sn-containing alloys are effectively refined, and the grains of the alloy with 0.90 wt%Sn are the finest. Compared with the ternary alloy, the tensile and creep properties of the alloys with the additions of 0.46 wt% and 0.90 wt%Sn are effectively improved. However, the ultimate tensile strength and elongation of the alloy with 1.88 wt%Sn are decreased though its yield strength and creep properties are improved. Among the three Sn-containing alloys with the additions of 0.46 wt%, 0.90 wt% and 1.88 wt%Sn, the alloy with 0.90 wt%Sn exhibits the relatively optimal tensile and creep properties.

The Influence of Tin on the Microstructure and Creep Properties of Mg-5Al-3Ca-0.7Sr-0.2Mn Magnesium Alloy

The paper presents results of microstructural investigations and creep properties of Mg-5Al-3Ca-0.7Sr-0.2Mn (ACJM53) and Mg-5Al-3Ca-0.8Sn-0.7Sr-0.2Mn (ACTJM531) magnesium alloys in as cast condition. The microstructure of the ACJM53 consists of α-Mg, (Mg,Al)2Ca - C36, Al3Mg13(Sr,Ca), Al2Ca - C15 and AlxMny. Additionally, the CaMgSn phase is observed in the ACTJM531 magnesium alloy. The addition of 0.8 wt% tin reduces the tensile strength at ambient temperature and creep resistance at 180°C.

Effects of Heat Treatment on Microstructure and Mechanical Properties of Mg-3Sn-2Ca Magnesium Alloy

The effects of heat treatment on the microstructure and mechanical properties of Mg-3Sn-2Ca alloy were investigated. The results indicate that after solutionized at 500 °C for more than 24 h, the morphology of the CaMgSn phase in the alloy changes from the continuous and/or quasi-continuous nets to the particle-like shape. Furthermore, after solutionized at 500 °C for 24 h, for a given aging temperature of 285 °C, with prolonging aging time the matrix hardness of the alloy increases, and attains the maximum at 32 h of aging time and beyond that it decreases. In addition, it is preliminarily inferred that heat treatment would give a beneficial effects on the tensile and creep properties of Mg-3Sn-2Ca alloy due to the modification of the CaMgSn phase.

Effects of minor additions of Ce and Y on as cast microstructure of Mg–3Sn–2Ca magnesium alloy

The effects of minor additions of Ce and Y on the as cast microstructure of Mg–3Sn–2Ca (wt-%) magnesium alloy are investigated and compared. Results indicate that adding minor Ce or Y to Mg–3Sn–2Ca alloy does not cause formation of any new phases in the alloy. The as cast Mg–3Sn–2Ca alloy with addition of 0·5 wt-%Ce or Y is still composed of α-Mg, CaMgSn and Mg2Ca phases. However, after adding 0·5 wt-%Ce or Y to Mg–3Sn–2Ca alloy, not only the formation of CaMgSn phase in the alloy is suppressed but also the CaMgSn phases in the alloy are effectively refined. In addition, adding 0·5 wt-%Ce to Mg–3Sn–2Ca alloy exhibits higher refinement efficiency to the CaMgSn phase in the alloy than adding 0·5 wt-%Y. Further investigations need to be considered in order to understand the difference of minor Ce and Y with regard to the refinement of CaMgSn phase in the Mg–3Sn–2Ca alloy.

Observation of Microstructural Refinement in Mg-3Sn-2Ca Magnesium Alloy Containing Minor Sr

The microstructures of the Mg-3Sn-2Ca magnesium alloys with and without adding minor Sr were investigated and compared. The results indicate that adding 0.1 wt.% Sr to the Mg-3Sn-2Ca alloy can effectively refine the primary CaMgSn phases and grains. In addition, in the alloy containing minor Sr the volume fraction of the primary and eutectic CaMgSn phases appears to be decreased, whereas the volume fraction of the Mg2Ca precipitates seems to be increased. The mechanism for the microstructural change in the alloy containing minor Sr is possibly related to the effects of Sr additions on the onset crystallizing temperature and undercooling degree.

Effects of zirconium addition on as-cast microstructure and mechanical properties of Mg–3Sn–2Ca magnesium alloy

At present, the mechanical properties of the Mg–3Sn–2Ca magnesium alloy are not satisfying and further enhance needs to be considered via further alloying/microalloying additions. The effects of Zr addition on the as-cast microstructure and mechanical properties of the alloy were investigated by using optical and electron microscopies, differential scanning calorimetry (DSC) analysis, and tensile and creep tests. The results indicate that adding 0.41, 0.76 or 1.18wt.% Zr can refine the grains of the alloy, and the primary CaMgSn phases in the Zr-containing alloys are changed from coarse needle-like net to relatively fine short block and/or particle-like shapes. As a result, the tensile and/or creep properties of the Zr-containing alloys are improved. Among the Zr-containing alloys, the alloy with the addition of 0.76wt.% Zr exhibits the relatively optimum mechanical properties.

Effects of Gd addition on as-cast microstructure and mechanical properties of Mg–3Sn–2Ca magnesium alloy

In the paper, the effects of Gd addition on the as-cast microstructure and mechanical properties of the Mg–3Sn–2Ca magnesium alloy were investigated. The results indicate that after adding 0.42–1.79wt.%Gd to the Mg–3Sn–2Ca alloy the GdMgSn phase is formed, and the primary CaMgSn phases are changed from coarse needle-like net to relatively fine short block and/or particle-like shapes. Furthermore, an increase in Gd amount from 0.42wt.% to 1.79wt.% causes the volume fraction of the CaMgSn and Mg2Ca phases to gradually decrease and increase, respectively. In addition, adding 0.42wt.%, 0.88wt.% or 1.79wt.%Gd to the Mg–3Sn–2Ca alloy can improve the tensile and creep properties of the alloy. Among the Gd-containing Mg–3Sn–2Ca alloys, the alloy added 0.42wt.%Gd exhibits the best tensile properties while the alloy added 1.79wt.%Gd has the best creep properties.