稀土Nd对AZ 31镁合金铸态组织和力学性能的影响

利用气氛电阻炉制备了AZ 31-xNd合金(x=0.05%,0.1%,0.2%,0.4%,0.6%),采用光学显微镜(OM)、扫描电子显微镜(SEM)和电子能谱分析仪(EDS)对不同Nd含量的实验合金进行了显微组织观察和分析,结果发现,Nd在AZ 31-xNd合金中形成了Al_3Nd和Mg_(12)Nd相,这些含Nd相导致AZ 31镁合金在凝固过程中的晶粒细化,从而提高了AZ 31镁合金的铸态室温力学性能,随着Nd含量的增加,合金的铸态室温抗拉强度极限和延伸率均先升高后降低.     

Effects of calcium,samarium addition on microstructure and mechanical properties of AZ61 magnesium alloy

The microstructure and mechanical properties of AZ61 magnesium alloy with Ca, Sm addition were investigated. The results showed that the addition of 0.5 wt.% Ca reduced the quantity of Mg17Al12 phase, and formed a new Al4 Ca phase which is reticular in AZ61 alloy. With the addition of Ca and Sm, the microstructure was further refined and new Al-Sm rich phases were formed in AZ61 alloy with 0.6 wt.%–1.5 wt.% Sm addition, the TEM analysis confirmed that they were Al2 Sm and Al4 Sm. Tensile tests showed that 1.0 wt.% Sm addition contributed to the formation of the Al2 Sm and Al4 Sm and the improvement in the ambient strength, i.e., an ultimate tensile strength of 327 MPa and an elongation of 10.1%. However, excessive Sm addition led to the coarsening of Al2 Sm and Al4 Sm phases, thus resulted in the decline of strength and plasticity.     

Effect of Sb on the microstructure and mechanical properties of AZ91 magnesium alloy

Effects of Sb addition on the microstructure, mechanical properties, and fracture behaviors of AZ91 magnesium alloy, as well as the sensitivity to section thickness of the structure and mechanical properties, have been studied. The results show that when Sb is added into the AZ91 alloy, the grain is refined, the Mg₁₇Al₁₂ phase is refined and granulated, and a new Mg₃Sb₂ phase is formed and becomes coarse needle-shaped as Sb content increases. The room-temperature tensile strength, elongation, and impact toughness increase first, and then decrease with increasing Sb content. The study on sensitivity to section thickness shows that, when composition is constant, the room-temperature tensile strength and elongation increase with the reduction of section thickness; when section thickness is constant, the room-temperature tensile strength and elongation increase first, and then decrease with increasing Sb content. Additionally, the Sb addition improves the tensile strength of the AZ91 alloy at 100 °C and 150 °C. The room-temperature tensile and impact fractographs of the AZ91 alloy show intergranular fracture. With increasing Sb content, the tearing deformation zones on the both fractographs enlarge at first, and then diminish, which is consistent with the change of tensile strength, elongation, and impact toughness increasing first, and then reducing with increasing Sb content.     

Effect of Sb on the microstructure and mechanical properties of AZ91 magnesium alloy

Effects of Sb addition on the microstructure, mechanical properties, and fracture behaviors of AZ91 magnesium alloy, as well as the sensitivity to section thickness of the structure and mechanical properties, have been studied. The results show that when Sb is added into the AZ91 alloy, the grain is refined, the Mg₁₇Al₁₂ phase is refined and granulated, and a new Mg₃Sb₂ phase is formed and becomes coarse needle-shaped as Sb content increases. The room-temperature tensile strength, elongation, and impact toughness increase first, and then decrease with increasing Sb content. The study on sensitivity to section thickness shows that, when composition is constant, the room-temperature tensile strength and elongation increase with the reduction of section thickness; when section thickness is constant, the room-temperature tensile strength and elongation increase first, and then decrease with increasing Sb content. Additionally, the Sb addition improves the tensile strength of the AZ91 alloy at 100°C and 150°C. The room-temperature tensile and impact fractographs of the AZ91 alloy show intergranular fracture. With increasing Sb content, the tearing deformation zones on the both fractographs enlarge at first, and then diminish, which is consistent with the change of tensile strength, elongation, and impact toughness increasing first, and then reducing with increasing Sb content.     

Effect of mischmetal on mechanical properties and microstructure of die-cast magnesium alloy AZ91D

Effects of the mischmetal addition in range of 0.4 wt.% to 1.7 wt.% on the microstructure and mechanical properties of die-cast magnesium AZ91D were investigated to improve the elevated temperature mechanical properties of the alloy by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile tests. The results revealed that mechanical properties of die-cast magnesium alloy AZ91D-0.4%MM at 100 oC were near to those of die-cast magnesium alloy AZ91D. The ultimate tensile strength, 0.2% proof yield strength and elongation to failure of die-cast magnesium alloy AZ91D at 170 oC were 178, 129 MPa and 20%, respectively. In comparison, the ultimate tensile strength, 0.2% proof yield strength and elongation to failure of die-cast magnesium alloy AZ91D-0.4%MM at 170 oC reached to 206, 142 MPa and 26%, respectively increased by 15.7%, 10% and 30%. Proper addition of mischmetal could enhance the mechanical properties at an elevated temperature, which was attributed to the formation of Al-RE phases with high thermal stability. Hence sliding of grain boundaries and cracks could be effectively hindered by Al-RE phases.     

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.     

Effect of strontium on the microstructure, mechanical properties, and fracture behavior of AZ31 magnesium alloy

The effect of strontium (Sr) on the microstructure, mechanical properties, and fracture behavior of AZ31 magnesium alloy and its sensitivity to cooling rate are investigated. Three phases—blocky-shaped Mg₁₇Al₁₂, acicular Mg₂₀Al₂₀Mn₅Sr, and insular Mg₁₆(Al,Zn)₂Sr—are identified in the Sr-containing AZ31 alloys. With increasing cooling rate, the blocky-shaped Mg₁₇Al₁₂ phase increases, the acicular Mg₂₀Al₂₀Mn₅Sr phase diminishes, and the insular Mg₁₆(Al,Zn)₂Sr phase is refined and granulated. The study suggests that the grain size decreases with increasing cooling rate for a given composition. However, the grain size decreases first, then increases, and finally decreases again with increasing Sr for a given cooling rate. The yield strength (σ _y ) of AZ31 magnesium alloy can be improved by grain refinement and expressed as σ _y =35.88+279.13d ^−1/2 according to the Hall-Petch relationship. The elongation increases when Sr is added up to 0.01 pct and then decreases with increasing Sr addition. Grain refinement changes the fracture behavior from quasicleavage failure for the original AZ31 alloy to mixed features of quasicleavage and microvoid coalescence fracture.     

The effect of the electromagnetic vabration on the microstructure, segregation, and mechanical properties of As-cast AZ80 magnesium alloy billet

The effect of the electromagnetic vibration on the properties of 300-mm-diameter AZ80 Mg billets was investigated. The experiments were performed both in the absence and in the presence of electromagnetic vibrating force fields, which were induced by an interaction of variable and stationary magnetic fields. In conventional direct-chill (DC) casting, the AZ80 billet exhibited large dendritic grains with severe segregations of Al and Zn. Applying the electromagnetic vibration during the casting led to significant grain refinement and to greatly reduced segregation in the billet. There was a significant increase in the tensile strength, hardness, and facture elongation of the as-cast AZ80 billet relative to that cast in the absence of the electromagnetic vibration. Microchemical analysis revealed that the application of electromagnetic vibration increased the minimum concentration of Al and Zn in the center of the Mg matrix.     

热拉拔工艺对AZ61镁合金丝材组织与性能的影响

采用自制热拉拔装置将AZ61镁合金粗挤压棒材拉拔成丝,研究拉拔温度、道次变形量等热拉拔工艺对单道次拉拔后丝材组织、力学性能的影响规律,并对拉拔过程中断丝情况进行统计,确定能够实现稳定热拉拔的工艺参数范围.结果表明,当道次变形量为15%时,随着温度的升高,丝材中的孪晶组织逐渐减少,强度逐渐降低,延伸率逐渐升高,丝材在350℃时发生动态再结晶.当拉拔温度一定时,随着道次变形量的增加,丝材的加工硬化程度增加,强度、硬度升高,延伸率下降.但当拉拔温度为300℃,道次变形量增加到25%时,丝材发生动态再结晶,使强度硬度下降,延伸率升高.过高的拉拔温度和道次变形量会使丝材发生断裂,随着温度的提高,丝材所能承受的最大变形量逐渐减小.     

Effect of magnesium addition on microstructure and mechanical properties in wheel steel

In order to reveal the effect of Mg in low carbon microalloy steel, low carbon microalloy steel of HR60 wheel steel was smelted in vacuum induction furnace and industrial field respectively. The characteristics of typical non- metallic inclusions and microstructure of experimental steels were both compared by OM, SEM- EDS and INCA Feature with automatically scanning inclusions function. The mechanical properties of the experimental steels were also measured. The results show that alumina inclusions are modified to spinel inclusions with small size after Mg addition. Furthermore, acicular ferrite can be induced effectively by inclusions containing magnesium. The microstructures of experimental steels are changed from ??polygonal ferrite(PF) + pearlite(P)??to ??polygonal ferrite(PF) + degenerate pearlite(DP) + acicular ferrite(AF)?? and refined by Mg treatment. The strength of experimental steels is improved with Mg addition. In industrial experiments, the fatigue limit of Mg- treated steels is greater than 460MPa, while the fatigue limit of Ca- treated steels is about 450MPa. In addition, the fatigue life of Mg- treated steels is generally higher than that of Ca- treated steels under the condition that the stress is greater than the fatigue limit. In laboratory experiments, the contents of Nb and Ti are reduced while Mg content in steel is 18??10-6, the strength of the wheel steel is close to the reference steel. Therefore, the project to reducing production cost by taking advantage of the microalloy role of Mg is feasible.     

Effect of cerium addition on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy

Effect of cerium addition on the microstructure and mechanical properties of an Al-Zn-Mg-Cu alloy have been investigated. In this study, aluminum alloys with up to 0.4% cerium content have been prepared by melting, metal mould casting followed by thermo-mechanical processing. The alloys were extensively characterized by optical and transmission electron microscopy, followed by mechanical property examination by tensile tests as well as nanoindentation tests. It was observed that cerium addition results in up to 5% grain refinement of the cast dendritic structure as well as up to 38% refinement of the heat treated microstructure. Transmission electron microscopy (TEM) has revealed the uniform distribution of fine GP zones and some semi coherent β(MgZn₂) precipitates in the Al rich matrix. Further TEM results show that when the Ce content was changed from 0.1% to 0.4%, precipitate size increased from 5 to 50nm and the precipitate morphology changed from spherical to needle shape. Evaluation of mechanical properties through tensile and nano-indentation tests have exhibited that both Young’s modulus and tensile strength increases with Ce addition up to 0.3% and subsequently decrease.     

非对称轧制对AZ31B镁合金组织及性能的影响

开展了非对称轧制对AZ31B镁合金晶粒细化影响的研究,分析了不同温度及不同压下率时宏观形貌和晶粒尺寸变化,并与对称轧制作了对比。结果表明,非对称轧制的整体晶粒尺寸比对称轧制更为细化;非对称轧制在温度为350 ℃、压下率为60%时晶粒最为细小均匀,上表面、中心层和下表面的平均晶粒尺寸分别为2.35、2.84和2.22 μm。在初轧温度为300～350 ℃范围内,组织产生充分动态再结晶;随着轧制温度继续升高,晶界产生充分迁移和扩散,晶粒随之长大,导致镁合金的综合性能变差。非对称轧制板材的抗拉强度和断后伸长率都优于对称轧制板材,在400 ℃轧制时,压下率为30%时获得较为优异的综合力学性能,抗拉强度为365.36 MPa,断后伸长率为34.9%。     

剧烈塑性变形对块状镁合金微观组织和力学性能的影响

等通道转角挤压（Equal channel angular pressing, 简称ECAP）可以使镁合金产生较大的塑性变形.通过有限元方法模拟了等通道转角挤压工艺及其相关工艺参数,研究了工件的应变和载荷分布情况,并建立了累积变形结果、微观组织细化和力学性能的数学模型.通过分析得到了晶粒细化和力学性能的关系,对累积变形的特点分析,预测了晶粒细化后的尺寸和力学性能.      

Effect of rare-earth element additions on high-temperature mechanical properties of AZ91 magnesium alloy

The present article focuses on the high-temperature mechanical properties of the magnesium alloy AZ91. The addition of rare-earth (RE) elements up to 2 wt pct improves both yield and tensile strengths at 140 °C by replacing the Mg₁₇Al₁₂ phase with RE-containing intermetallic compounds. This intermetallic phase is thermally and metallurgically stable and is expected to boost the grain-boundary strengthening. It also increases the resistance of grain boundaries to flow at high temperatures. Further increases of RE additions reduce strength and ductility due to growth of the Al₁₁RE₃ brittle phase, which has sharp edges. Still, at a 3 wt pct RE addition, the strength of the alloy at high temperatures is more than that of AZ91.     

喷射沉积AZ31镁合金微观组织与力学性能

采用喷射沉积方法制备了AZ31镁合金沉积柱坯,利用热轧作为后续加工,研究了镁合金的组织变化及材料的性能.实验结果表明:沉积态合金组织均匀,晶粒细小(平均晶粒尺寸约为20μm);热轧变形的致密化过程、动态再结晶以及退火再结晶使合金具有良好的组织结构和力学性能;轧制态试样断口呈现为脆性解理断裂方式,退火态试样断口则表现为脆性和韧性断裂混合机制.     

不同磁场作用对AZ31镁合金的凝固组织的影响

镁合金是具有优越性能的金属材料,镁合金的加工是目前国内外正在深入进行研究的新课题.实验发现在镁合金的凝固过程中施加低频或静态磁场都能细化晶粒,但静磁场得到的细化效果要优于低频交流磁场,同时随磁感应强度的增加,静磁场细化晶粒的效果明显提高;在静磁场条件下晶界共晶体组织的厚度明显减小,同时在晶内出现了大量细小块状化合物,这有利于改善镁合金的综合性能.     

Effects of samarium addition on as-cast microstructure,grain refinement and mechanical properties of Mg-6Zn-0.4Zr magnesium alloy

In this paper, the microstructural evolution, grain refinement and mechanical properties of as-cast Mg-6Zn-0.4Zr alloys with varying Sm contents(0, 2 wt.%, 4 wt.% and 6 wt.%) were investigated by using an optical microscope(OM), a scanning electron microscope(SEM) equipped with energy dispersive spectroscope(EDS), an X-ray diffractometer(XRD) and mechanical tests at room temperature, respectively. The experimental results indicated that the addition of Sm could obviously refine the as-cast grains, modify the eutectic morphology and affect the mechanical properties of the alloys. The main phases in Mg-6Zn-xSm-0.4Zr alloys included matrix α-Mg, Mg_2Zn_3, Mg_(41)Sm_5 and MgZ nS m. With Sm content increasing to 4%, the MgZ nS m phase was created, meanwhile, the morphology of some eutectic phases revealed apparently lamellar structure, which had a bad effect on the mechanical properties. In addition, the maximum values of ultimate tensile strength(UTS, 214 MPa) and elongation(EL, 7.42%) were simultaneously obtained from the alloy with 2% Sm. However, Sm addition had no obvious effects on the fracture behavior of the alloys, namely, the fracture pattern of Mg-6Zn-0.4Zr alloy belonged to inter-granular and brittle modes while the fracture regimes of all the Sm-containing alloys were dominated by the mixture of inter-granular and trans-granular modes.     

热处理对含Y元素AZ31镁合金板材组织和性能的影响

对含Y元素AZ31镁合金板材进行退火处理后的组织和性能进行了研究.结果表明:随着退火温度的升高,镁合金晶粒尺寸逐渐增大,力学性能略有提高然后降低;退火时间对镁合金晶粒尺寸影响不大;在300℃下退火1 h后板材性能达到最佳,抗拉强度为255 MPa,屈服强度为170 MPa,延伸率为24%;经过热处理后镁合金断裂方式为准解理断裂和韧性断裂的复合形式.     

烧结温度对SiO_2颗粒强化AZ91镁合金组织与性能的影响

采用元素粉球磨法,添加3%Si O2(质量分数,下同)作为增强颗粒,热压烧结制备出Si O2颗粒增强AZ91镁合金,并对其显微结构和室温力学性能进行测试分析。结果表明:当热压烧结温度低于580℃时,随温度升高,材料密度提高,晶粒大小未发生明显变化;但烧结温度超过580℃后,材料密度有所下降,晶粒明显长大,抗拉强度下降。AZ91-3%Si O2最佳热压烧结温度为580℃,材料的抗拉强度达114 MPa。     

Comparison of effects of cerium, yttrium and gadolinium additions on as-cast microstructure and mechanical properties of Mg-3Sn-1Mn magnesium alloy

The effects of Ce, Y and Gd additions on the as-cast microstructure and mechanical properties of Mg-3Sn-1Mn alloy were investigated and compared by using optical and electron microscopies, X-ray diffraction analysis, and tensile and creep tests. The results indicated that the microstructure of the Mg-3Sn-1Mn alloy with the addition of 0.87 wt.%Ce was refined while the microstructures of the alloys with the additions of 0.79 wt.%Y or 0.84 wt.%Gd were coarsened. Furthermore, adding 0.87 wt.%Ce to the Mg-3Sn-1...