Effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy

The effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy was investigated. The results indicate that adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can effectively refine the as-cast microstructure of the alloy, and the CaMgSn phase with high thermal stability is formed in the alloy. In addition, adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can also improve the creep properties of the alloy. After adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy, the second creep rate of the alloy at 150°C and 50 MPa for 100 h decreases from 4.67 × 10⁻⁸ to 1.43 × 10⁻⁸ s⁻¹. The strengthening mechanism is mainly attributed to the microstructural refinement and the formation of CaMgSn phase.     

Microstructure and creep properties of Mg-4Al-2Sn-1 （Ca,Sr） alloys

The effects of Ca and Sr addition on the microstructure and creep properties of Mg-4Al-2Sn alloys were examined.Tensile tests at 25℃ and 200℃ and creep tests at 150℃ and 200℃ were carried out to estimate the room temperature and high temperature mechanical properties of these alloys.The microstructure of the Mg-4Al-2Sn alloy showed dendriticα-Mg,Mg17Al12 and Mg2Sn phases.The latter two phases precipitated along the grain boundaries.The addition of Ca and Sr resulted in the formation of ternary CaMgSn and SrMgSn phases within the grain.The grain size was reduced slightly with the addition of Sr and Ca.The tensile strength was decreased by the addition of Ca and Sr at room temperature.However,the high temperature tensile strength was increased.The creep strength was improved by the addition of Ca and Sr.     

Effects of Minor Zr and Sr on As-Cast Microstructure and Mechanical Properties of Mg-4Y-1.2Mn-1Zn (wt.%) Magnesium Alloy

The effects of minor Zr and Sr on the as-cast microstructure and mechanical properties of the Mg-4Y-1.2Mn-1Zn (wt.%) alloy were investigated using optical and electron microscopies, differential scanning calorimetry (DSC) analysis, and tensile and creep tests. The microstructural results indicate that small additions of Zr and/or Sr to the Mg-4Y-1.2Mn-1Zn alloy do not cause an obvious change in the morphology and distribution of the Mg₁₂YZn phase in the alloy. The tensile and creep tests indicate that, although small additions of Zr and/or Sr to the Mg-4Y-1.2Mn-1Zn alloy do not have obvious effects on the creep properties of the alloy, the tensile properties at room temperature and 300 °C for the alloys added with Zr and/or Sr are improved. Among the Zr- and/or Sr-containing alloys, the alloy specifically added with of 0.5 wt.% Zr + 0.1 wt.% Sr obtains the optimum tensile properties, and is followed by the alloys added with 0.5 wt.% Zr and 0.1 wt.% Sr.     

Effect of Ca addition on microstructure and impression creep behavior of cast AZ61 magnesium alloy

Microstructure and creep properties of AZ61 alloy containing 1 and 3 wt.% Ca were investigated. The creep properties were examined using impression method under different stresses between 200 and 500 MPa at the temperature ranging from 423 to 491 K. The microstructure of AZ61 alloy contains α(Mg) matrix and Mg₁₇Al₁₂ intermetallic phases. It is shown that adding Ca to AZ61 alloy reduces the amount of Mg₁₇Al₁₂ phase via forming (Mg, Al)₂Ca phase; furthermore, increasing the Ca content to 3 wt.% leads to the formation of (Mg, Al)₂Ca phase, as well as the elimination of the Mg₁₇Al₁₂ phase. Creep properties of AZ61 alloy are improved with the Ca addition. The improvement in creep properties is attributed to the reduction in the amount of Mg₁₇Al₁₂ phase and the formation of (Mg, Al)₂Ca phase with high thermal stability. According to the obtained creep data, it is concluded that the pipe diffusion−climb controlled dislocation creep is the dominant creep mechanism and Ca addition has no influence on this mechanism. The effect of pre-deformation on the creep properties of AZ61+3%Ca alloy reveals that the creep resistance of the alloy depends on the continuity of (Mg, Al)₂Ca phase. It is decreased by reducing the phase continuity.     

Elevated temperature properties of Mg- 12Li-Al-MgO composites

1 Introduction Mg-Li alloys have potential for use in aerospace applications because they are exceptionally light and their specific stiffness is high[1?3]. However, there are some practical difficulties, such as poor creep behavior and microstructural in…     

Effects of minor Ca on as-cast microstructures and mechanical properties of Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys

The effects of the addition of 0.6% Ca (mass fraction) on the as-cast microstructure and mechanical properties of the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc magnesium alloys were investigated and compared by optical microscopy and scanning electron microscopy, differential scanning calorimetry analysis, and tensile and creep tests. The results indicate that the addition of 0.6% Ca to the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys can refine the grains of the two alloys. At the same time, the addition of 0.6% Ca to the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys can effectively improve the tensile properties of the two alloys. In addition, the addition of 0.6% Ca can also improve the creep properties of the Mg-3Ce-1.2Mn-0.9Sc alloy but is not beneficial to the creep properties of the Mg-4Y-1.2Mn-0.9Sc alloy. The different effects of minor Ca on the creep properties of the Mg-3Ce-1.2Mn-0.9Sc and Mg-4Y-1.2Mn-0.9Sc alloys are possibly related to the difference in the solid solubilities of Ce and Y in Mg.     

Comparison of as-cast microstructure,tensile and creep properties for Mg-3Sn-1Ca and Mg-3Sn-2Ca magnesium alloys

The as-cast microstructure,tensile and creep properties of Mg-3Sn-1Ca and Mg-3Sn-2Ca magnesium alloys were investigated and compared by using optical microscopy and scanning electron microscopy,X-ray diffraction analysis and tensile tests. The results indicate that the as-cast microstructures of Mg-3Sn-1Ca and Mg-3Sn-2Ca alloys are different.The former is mainly composed ofα-Mg,eutectic CaMgSn and solid state precipitation of Mg 2 Sn,whereas the latter is mainly composed ofα-Mg, primary CaMgSn,eutectic CaMgSn and Mg2Ca phases.As a result,the two alloys obtain different tensile and creep properties. Mg-3Sn-1Ca alloy shows relatively higher ultimate tensile strength and elongation at room temperature and 150℃than Mg-3Sn-2Ca alloy,however,the yield strengths of Mg-3Sn-1Ca alloy at room temperature and 150℃are relatively low.In addition,the creep properties of Mg-3Sn-1Ca alloy at 150℃and 70 MPa for 100 h are obviously lower than those of the Mg-3Sn-2Ca alloy.     

Microstructure,tensile properties and compressive creep resistance of Mg-(5-8.5)%Sn-2%La alloys

The microstructure,tensile properties and compressive creep resistance of permanent-mould cast Mg-(5-8.5)%Sn-2%La (mass fraction) alloys were investigated.The results show that Mg-(5-8.5)%Sn-2%La alloys are all composed ofα-Mg phase, Mg_2Sn and Mg-La-Sn compounds.Compared with those of Mg-5%Sn binary alloy,the grain size and the content of Mg_2Sn compound in Mg-5%Sn-2%La alloy are decreased.With the increase of Sn content in Mg-(5-8.5)%Sn-2%La alloys,the content of Mg_2Sn compound increases,while that of...     

Microstructure and corrosion behavior of Mg-Sn-Ca alloys after extrusion

Mg-Sn-Ca alloys promise a reasonable corrosion resistance in combination with good creep resistance, likely due to the presence of Ca2-xMgxSn and other phases. The selected alloys with 3% Sn and Ca in the range of 1%-2% have been extruded in order to achieve more homogeneous microstructure compared with the as-cast alloys. Optical microscopy(OM) and X-ray diffraction(XRD) techniques were used to study the microstructure and phases of these alloys. The corrosion behavior of these alloys was investigated by means of salt spray test and potentio-dynamic measurements. The results obtained on the alloys Mg-3Sn (T3), Mg-3Sn-1Ca (TX31), and Mg-3Sn-2Ca (TX32) indicate the presence of the same phases in as-cast and after extrusion, namely Mg2Sn, Ca2-xMgxSn, and Ca2-xMgxSn/Mg2Ca, respectively. However, due to the occurrence of extensive recrystallization in the extrusion process, the grain size has significantly reduced after extrusion. The reduction leads to the improvement of the corrosion resistance after extrusion which is then comparable with the commercial alloy AZ91D.     

Microstructure and Mechanical Properties of Mg-8Li-(0, 1, 2)Ca-(0, 2)Gd Alloys

A series of new Mg-8Li-xCa-yGd (x = 0, 1, 2; y = 0, 2; wt.%) alloys were prepared, and the microstructure and mechanical properties were investigated. The mechanical properties were characterized by tensile, compression and bending tests at room temperature. The results show that Mg-8Li-1Ca alloy is composed of alpha(Mg), beta(Li) and CaMg₂ phases. In addition to the same phases in Mg-8Li-1Ca, there also exists CaLi₂ phase in Mg-8Li-2Ca. In addition to the same phases in Mg-8Li-2Ca, GdMg₅ phase is also formed in Mg-8Li-1Ca-2Gd alloy due to the addition of Gd. Both Ca and Gd have refining effect in the alloys, and the refining effect of Ca is better than that of Gd. The additions of Ca and Gd can improve the tensile strength and yield strength, but decrease the elongation and the bending strength. Comparing the mechanical properties of the investigated alloys, Mg-8Li-1Ca-2Gd possesses the best mechanical properties.     

Effects of calcium addition on as-cast microstructure and mechanical properties of Mg-5Zn-5Sn alloy

The effects of Ca addition on the as-cast microstructure and mechanical properties of the Mg-5Zn-5Sn (mass fraction,%) alloy were investigated.The results indicate that an addition of 0.5%-1.5% (mass fraction) Ca to the Mg-5Zn-5Sn alloy not only refines the as-cast microstructure of the alloy but also causes the formation of the primary and/or eutectic CaMgSn phases with high thermal stability;an increase in Ca amount from 0.5% to 1.5% (mass fraction) increases the amount and size of the CaMgSn phase.In addition,Ca addition to the Mg-5Zn-5Sn alloy improves not only the tensile properties at room temperature and 150 ℃ but also the creep properties.Among the Ca-containing Mg-5Zn-5Sn alloys,the one added 0.5% (mass fraction) Ca obtains the optimum ultimate tensile strength and elongation at room temperature and 150 ℃,however,the alloy added 1.5% (mass fraction) Ca exhibits the optimum yield strength and creep properties.     

Microstructure and Mechanical Properties of a Ag Micro-Alloyed Mg-5Sn Alloy

Effects of 1.5 wt.% Ag addition and solid solution?+?artificial ageing at 160 °C on the microstructure and mechanical properties of a Mg-5Sn alloy have been studied. The results show that Ag addition has significantly hardened the solution-treated Mg-5Sn alloy. During the ageing process, the hardness increase rate and the strength and ductility of the Mg-5Sn alloy at each state are also improved by Ag addition. The improved strengthening behavior is primarily attributed to the refinement distribution of the Mg₂Sn precipitates, the enhanced precipitation process, and the synergistic strengthening effect of Mg₂Sn and a metastable plate DO₁₉ phase formed at lower ageing temperature. For each solution-treated alloy, the strength and ductility are higher than the corresponding cast ones. Ageing further enhances the yield strength, and the ductility of the Mg-5Sn-1.5Ag alloy is also increased after ageing. The fracture surfaces of the both peak-aged alloys exhibit the characteristic of a mixture of quasi-cleavage and ductile fracture.     

Enhancement of mechanical properties of duplex Mg-9Li-3Al alloy by Sn and Y addition

For enhancement of mechanical properties in Mg-9Li-3Al alloys, Mg-9Li-3Al duplex alloys were alloyed by addition of Sn and Y. Microstructure evolution and mechanical property response of as-cast Mg-9Li-3Al alloys by alloying with Sn and Y were investigated by optical microscopy, scanning electron microscopy, X-ray diffractometry and tensile tests. The results indicate that considerable blocky dendrites of primary α phase in Mg-9Li-3Al alloys become lath-like due to the addition of Sn. With addition of Y, Mg-9Li-3Al alloy consists of both block-like and lath-like α-Mg dendrites. The as-cast Mg-9Li-3Al-1Sn-1Y alloy shows a yield strength of 118 MPa, ultimate tensile strength of 148 MPa and the elongation to failure of 21%. Improvement in both strength and elongation of Mg-9Li-3Al alloys with Sn and Y addition is attributed to the combined action of MgLi₂Sn and Al₂Y intermetallic compounds.     

Effect of Ce on microstructure, mechanical properties and corrosion behavior of high-pressure die-cast Mg-4Al-based alloy

Mg-4Al-xCe-0.3Mn (x = 0, 1, 2, 4 and 6 wt.%) alloys were prepared by high-pressure die-casting. The microstructures, mechanical properties and corrosion behavior were investigated. The cross-section of test bar is divided into the fine skin region and the relatively coarse interior region by a narrow band. The dendritic arm spacing is greatly reduced and the secondary phases Al₁₁Ce₃ and (Al, Mg)₂Ce with the former being the dominant one substitute the Mg₁₇Al₁₂ phase with addition of Ce. When Ce content reaches 4 wt.%, the alloy exhibits an optimal cost performance ratio. The improved mechanical properties maintained up to 200 °C are mainly related to the fine grain size and the main strengthening phase Al₁₁Ce₃, which is present in a high volume fraction, and possesses fine acicular morphology and relatively good thermal stability. The improved corrosion resistance is attributed to the microstructure modification of the alloys and the corrosion product films.     

Microstructure and hydrogen storage properties of Mg-Sn nanocomposite by mechanical milling

To improve the hydrogen storage properties, the composition and microstructure of Mg-Sn alloys were modified through fabricating Mg/Mg₂Sn nanocomposite by mechanical alloying. The microstructures were characterized by X-ray diffraction and scanning electron microscopy. It is found that Mg₂Sn instead of Mg(Sn) solid solution is preferably formed during milling process. Although Mg₂Sn is not a hydriding phase, the in situ formed nanosized Mg₂Sn facilitates hydrogen absorption/desorption of Mg by forming Mg/Mg₂Sn nanocomposite. The mechanically milled Mg-5 at.% Sn nanocomposite exhibits slightly elevated plateau pressure and destabilized thermodynamics due to the introduction of large amount of interface energy in Mg/Mg₂Sn nanocomposite.     

Effect of Sn content on microstructure and tensile properties of as-cast and as-extruded Mg−8Li−3Al−(1,2,3)Sn alloys

The effects of Sn content on microstructure and tensile properties of as-cast and as-extruded Mg−8Li−3Al− (1,2,3)Sn (wt.%) alloys were investigated by X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and tensile test. It is found that, as-cast Mg−8Li−3Al−(1,2,3)Sn alloys consist of α-Mg+β-Li duplex matrix, MgLiAl₂ and Li₂MgSn phases. Increasing Sn content leads to grain refinement of α-Mg dendrites and increase in content of Li₂MgSn phase. During hot extrusion, complete dynamic recrystallization (DRX) takes place in β-Li phase while incomplete DRX takes place in α-Mg phase. As Sn content is increased, the volume fraction of DRXed α-Mg grains is increased and the average grain size of DRXed α-Mg grains is decreased. Increasing Sn content is beneficial to strength but harmful to ductility for as-cast Mg−8Li−3Al−(1,2,3)Sn alloys. Tensile properties of Mg−8Li−3Al− (1,2,3)Sn alloys are improved significantly via hot extrusion and Mg−8Li−3Al−2Sn alloy exhibits the best tensile properties.     

Zn元素对Mg-7Y-3Sm-0.5Zr合金显微组织和力学性能的影响(英文)

研究添加Zn元素对铸造Mg-7Y-3Sm-0.5Zr合金的显微观组织和力学性能的影响。蠕变测试的温度范围为200-300 °C,应力范围为50-120 MPa。在本研究的蠕变测试条件下,合金的蠕变激活能为156-221kJ/mol。采用光学显微镜、扫描电镜和透射电镜观察合金在蠕变过程中显微组织的演化。结果表明:尽管合金在250 °C以下有着相似的蠕变行为,仅添加1%的Zn元素就能使合金在300 °C和50MPa蠕变条件下的蠕变寿命从52.2h提高到152.8h,表明Zn元素能够提高合金的高温抗蠕变性能。加入Zn元素后,合金中形成的高温稳定相和片层状结构相是合金高温抗蠕变性能提高的根本原因。     

Hot hardness and creep of Fe3Al-based alloys

Hot hardness and creep studies were carried out on Fe₃Al and Fe₃Al containing Cr or Ti. Indentation and impression creep testing methods were employed to characterize the creep behaviour. Compared to the binary alloy, Fe₃Al–Cr exhibits a lower hardness indicating solid-solution softening effect of Cr. On the other hand, solid-solution hardening effect of Ti is significant in the temperature range 300–900 K. Results from indentation creep indicates that a power-law creep behaviour (n between 6 and 8) is observed in the binary and Cr containing alloys at temperatures greater than 753 K. At lower temperatures in the above two alloys and in the Ti-containing alloy even at higher temperatures, there is a power-law break down. On the other hand at low stress levels covered in the impression creep studies, power-law creep is observed in all the alloys in the stress and temperature range of investigation. Under these conditions, all the alloys exhibit a stress exponent value of around 3 for the steady state creep rate. The activation energy for creep is estimated to be in the range 325 and 375 kJ mol. Among the alloys studied, Fe₃Al–Ti exhibits the best creep resistance. The results indicate that in the B2 region, viscous glide controls the creep rate at low stresses while climb of dislocations may be rate controlling at higher stresses.     

Ga含量对Al-Mg-Ga-Sn合金组织和降解性的影响

采用电炉熔炼制备了不同Ga含量的Al-Mg-Ga-Sn合金。通过光学显微镜(OM) 、扫描电镜(SEM)和X射线衍射仪(XRD)对其显微组织的形貌和成分进行了表征;在30℃、40℃、70℃、90℃的纯水中进行降解速率的测定;采用电化学工作站测试了室温电化学性能。结果表明：Al-Mg-Ga-Sn合金在Mg+Sn为定值10wt.%的情况下,Ga含量分别为0 wt.%、4 wt.%、8 wt.%、12 wt.%、16 wt.%时,合金组织均有铝基体相和Mg<sub>2</sub>Sn相,且随着Ga含量的增加合金组织中出现了Ga<sub>5</sub>Mg<sub>2</sub>相。Al-Mg-Ga-Sn合金的降解性特点是主要由铝基体相中点蚀开启,由Mg<sub>2</sub>Sn和Ga<sub>5</sub>Mg<sub>2</sub>化合物相的晶间腐蚀加速;不同Ga含量合金的起始降解温度由固溶于铝基体中的低熔点元素(Ga+Sn)的含量决定;相同Ga含量的合金随温度升高降解速率加快,降解反应动力学遵从阿伦尼乌斯公式。室温电化学分析表明：Al-Mg-Ga-Sn合金随Ga含量增加,腐蚀电位不同程度地负移,腐蚀电流逐渐增大。