Influence of impurities on microstructure and mechanical properties of ZK60 magnesium alloy

The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy, scanning electron microscopy and tensile test. ZK60 alloys were prepared by changing holding time of alloy melt during semi-continuous casting in order to control the content of impurity elements. The alloy with lower purity content is found to have less second precipitates and larger grain size in the as-cast state. However, in the as-extruded state, reducing impurities brings about a decrease in grain size and an increase in yield strength from 244 MPa to 268 MPa, while the elongations in the as-extruded alloys with different contents of impurities are almost the same. After T5 treatment, impurity content is found to have more obvious effect on the yield strength of ZK60 alloy. The yield strength of ZK60-45 alloys with low impurity content is increased up to 295 MPa after T5 treatment.     

High damping capacities of Mg-Cu based alloys

The dynamic mechanical analyzer (DMA) was applied to investigate the damping properties of Mg-Cu based alloys. The results show that the as-cast hypoeutectic Mg-Cu binary alloys exhibit ultra-high damping capacities, while the eutectic Mg-Cu alloy exhibits low damping capacity. The strain amplitude dependent damping performance reveals that the dislocation damping mainly dominates in Mg-Cu alloys. Furthermore, the influence of eutectic phase on damping mechanisms of Mg-Cu binary alloys was discussed in detail and the effect of Si addition on the damping of Mg-1%Cu based alloy was also reported. Two damping peaks are observed on the temperature dependent spectrum of Mg-Cu based alloys. One is located at room temperature, which is dislocation related peak; and the other is located at moderate temperature, which is caused by the grain boundary sliding.     

ZL401合金的阻尼行为研究

对铸态ZL401合金进行了低温人工时效处理，利用低频内耗测试技术研究了合金的阻尼性能及实模量与应变振幅、频率和温度的关系，并与铸态合金进行了对比。发现合金阻尼与应变振幅及应变频率相关，随温度的提高而增大，且在低温和高温时合金阻尼与频率的关系出现了相反的变化。ZL401合金振动过程中实模量的亏损随频率的降低和温度的升高而增大。认为ZL401合金的阻尼行为是界面阻尼和位错阻尼二者效应叠加的结果，室温阻尼主要归功于位错阻尼，而高温阻尼主要归功于界面阻尼。     

Microstructure,mechanical properties,and corrosion resistance of Mg–9Li–3Al–1.6Y alloy

Mg–9Li–3Al–1.6Y alloys were prepared through mixture method. The microstructure, mechanical properties, and corrosion resistance of the as-cast and asextruded alloys were studied by optical microscopy(OM),scanning electronic microscopy(SEM), X-ray diffraction(XRD), mechanical properties testing, and electrochemical measurement. The as-cast Mg–9Li–3Al–1.6Y alloy with the average grain size of 325 lm is composed of b-Li matrix, block a-Mg, and granule Al_2Y phases. After extrusion, the grain size of the as-cast alloy is obviously refined and reaches to 75 lm; the strength and elongation of the extruded alloy are enhanced by 17.20 % and49.45 %, respectively, owing to their fine microstructure and reduction of casting defects. The as-extruded alloy shows better corrosion resistance compared to the as-cast one, which may be related to the low stored energy and dislocation density in the extruded alloy, also the homogenization treatment before extrusion.     

AZ91镁合金的应变疲劳行为研究

研究了铸态和挤压态AZ91镁合金的室温应变疲劳行为。结果表明,铸态镁合金表现为循环应变硬化,而挤压态镁合金可呈现循环应变硬化、软化或循环稳定。与此同时,对两种状态的AZ91镁合金的应变寿命行为和循环应力-应变行为进行了分析测试,确定了相应的室温应变疲劳参数。此外,利用扫描电子显微镜观察分析了铸态和挤压态AZ91镁合金的疲劳裂纹萌生和扩展行为。     

Effect of small tensile deformation on damping capacities of Mg-1%Al alloy

Tensile tests with small deformation amounts of 0.5%, 1%, 3% and 5% were performed at room temperature on as cast Mg-1%Al alloy. Microstructures of the Mg-1%Al alloys before and after deformation were observed by optical microscopy (OM) and transmission electron microscopy (TEM). The strain amplitude dependent and temperature dependent damping capacities of the as-cast and deformed Mg-1%Al alloys were investigated by dynamic mechanical analysis (DMA). The mechanism of deformation on damping capacity of Mg-1%Al alloy was discussed. The results show that the as-cast Mg-1%Al alloy has high damping value at high strain. When the tensile elongation is higher than 3%, the damping values of this alloy in high strain region are significantly decreased at room temperature. But the large amount of dislocations produced by tensile deformation are activated by heat, and then increase the damping value at high temperature.     

铸态和挤压变形态Mg-Zn-Al-Re镁合金的室温和高温力学性能

采用透射电子显微镜、扫描电子显微镜及能谱分析、拉伸力学性能测试等手段比较分析了铸态和挤压变形态Mg-7Zn-3Al-0～0.7Re(质量分数,%)镁合金的室温和高温力学性能,探讨了稀土和变形加工对合金强度和塑性的影响规律。结果表明,适量稀土Er可以显著提高铸态Mg-Zn-Al合金的高温塑性,而稀土含量对合金室温力学性能和高温屈服强度影响不明显;挤压变形过程中动态弥散析出纳米级的球形析出相,显著提高Mg-Zn-Al-Er合金的高温力学性能,其200℃下的屈服强度和延伸率分别较铸态提高了105%和120%,断口显示其断裂方式呈明显的韧性断裂特征。     

Effects of Ce on damping capacity of AZ91D magnesium alloy

1　INTRODUCTIONThedampingcapacityisameasureoftheenergydissipatedduringmechanicalvibrationinthematerialsorcomponent .Metallicmaterialshavinghighdamp ingcapacitybecomevaluableinsuppressingmechani calvibrationandattenuatingwavepropagationforthecontrolofnoiseandthestabilizationofstructures .Takinghighdampingmetallicmaterialsasstructuralpartscouldeliminatetheneedforspecialenergyab sorbersordamperstoattenuatethevibrationandnoise ,inspiteofmostofthefrequentlyusedmetalsandalloys ,whichexhibitarela…     

Mg-Bi合金的显微组织和力学性能

采用挤压铸造和挤压变形工艺制备了Mg-Bi二元合金,通过金相显微镜分析,室温拉伸性能测试,X射线衍射分析,SEM和EDS等手段,研究了Mg-Bi合金在铸态和热挤压态的显微组织和力学性能.结果表明:铸态Mg-Bi合金随着Bi含量的增加,伸长率逐渐降低,抗拉强度逐渐增加,当Bi含量达10wt.％以上,抗拉强度降低;Mg-Bi合金铸锭经450℃、3h保温,挤压比为12.76热挤压后,随Bi含量的增加,抗拉强度与伸长率均逐渐增加,当Bi含量达12wt.％时,抗拉强度为219.68 MPa,伸长率为13.43％,Bi含量继续增加,合金抗拉强度及伸长率呈下降趋势;挤压态Mg-Bi合金的力学性能是晶粒细化与Mg3Bi2综合作用的结果,当Bi含量大于12wt.％后,形成较多粗大的Mg3Bi2相是导致合金力学性能下降的主要原因.     

Improved Corrosion Resistance in AZ61 Magnesium Alloys Induced by Impurity Reduction

The effect of impurity element Fe on corrosion behavior of AZ61 magnesium alloys in various states has been investigated by immersion test and hydrogen evolution measurements in 3.5% sodium chloride solution.The corrosion rate is found to relay on the impurity Fe concentration in the alloys and decreases with decreasing Fe content.When Fe content drops from 150 ppm to 10 ppm,the corresponding corrosion rates under as-cast and solution treatment conditions are reduced from 8.54 mm/a and 8.61 mm/a to 2.54 mm/a and 0.21 mm/a,respectively.The corrosion pattern of the AZ61 alloys is the localized corrosion,and the galvanic couples are formed among the impurity particles,second-phase particles and the matrix.The Fe impurity particles tend to act as main cathodic to form micro-galvanic cell with the α-Mg matrix,which is harmful for corrosion resistance of AZ61 alloy.     

挤压态Mg-6Zn-xEr合金的微观结构和力学性能

研究铸态、挤压态和挤压峰值态的Mg-6Zn-xEr合金的微观组织和力学性能。结果表明,Er的加入可显著改善Mg-6Zn合金的力学性能,经过峰值时效后合金的力学性能得到进一步提高;挤压态Mg-6Zn-0．5Er合金经过峰值时效处理后具有最佳的拉伸强度。该合金的抗拉强度和屈服强度分别为329MPa和183MPa,伸长率为12％。这表明添加0．5％Er可显著提高Mg-6Zn合金的时效硬化行为。挤压峰值态Mg-6Zn-0．5Er合金较好的力学性能归因于结构的细化和β1相的析出强化。     

Microstructure and damping properties of MnCuNiFeCe alloy

Mn-Cu alloys could exhibit high damping ability and excellent mechanical properties after proper heat treatment. In order to reduce the influence of impurity elements on damping capacity of Mn-Cu alloys, rare element cerium(Ce) was added into MnCuNiFe alloys. It is indicated that the contents of C, S and Si which have adverse effects on the damping capacity decrease and the grains are refined with the Ce content increasing. The microstructure of the MnCuNiFeCe alloy was investigated by X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscopy(TEM). The damping ability(tanδ) of the alloy was characterized by dynamical mechanical analyzer(DMA). It is found that the damping ability(tanδ) retains a very high level which is all above 0.05 from the temperature of-50 to 75 °C with the addition of Ce element. It is expected that the Ce alloying MnCuNiFe alloy with refined grains could find wide applications in the field of industry.     

Precipitation and responding damping behavior of heat-treated AZ31 magnesium alloy

Microstructure observation and dynamic mechanical analysis were carried out to investigate the precipitation and responding damping behaviors of AZ31 magnesium alloy. All the strain amplitude-dependent damping curves of the aged alloys are located between the curves of solutionized and as-cast alloys, although they have different critical strain amplitudes. The G-L theory is employed to explain the damping mechanism involving the interaction between the dislocation and the precipitated phase. In addition, a damping peak is observed at temperatures close to 330 ℃ for AZ31 magnesium alloy, which is related to the β-Mg₁₇Al₁₂ phase dissolution.     

Sr含量对Mg-Li-Al-Mn合金显微组织及力学性能的影响

利用真空感应炉在氩气保护下,设计与制备Mg-8Li-3Al-0.5Mn-xSr（x=0-1.0）合金,并将其进行热挤压处理。分别研究合金铸态与挤压态显微组织和拉伸性能。结果表明：LAM830合金主要含有α-Mg,β-Li,Al2Mn3和LiMgAl2相。在加入Sr后合金中出现Al-Sr析出相。Sr对铸态合金α-Mg基体的二次枝晶臂有明显细化效果。经过热挤压处理的合金组织远优于铸态的合金组织。金属间化合物的含量与形态对合金力学性能的影响很大,其中挤压态的LAM830-0.5Sr具有最佳的伸长率（22.43%）,LAM830-0.75Sr合金具有最佳的抗拉强度（265.46 MPa）。     

高阻尼镁合金Mg-0.6%Zr和Mg-Ni中内耗峰分析

在高阻尼镁合金研究中,发现了与合金室温下高阻尼性能有关的宽的弛豫内耗峰,该峰为位错内耗峰;该峰是基面位错在热激活作用下运动与点缺陷（空位与溶质原子）相互作用产生。同时在高阻尼合金Mg-Ni和Mg-0.6%Zr中发现了晶界内耗峰。有必要指出的是合金的显微组织会影响晶界弛豫：随着Ni的质量分数增加,晶粒细化同时晶界内耗峰向低温处迁移;同Mg-0.6%Zr合金相比,加入少量的Y后,Mg-0.6%Zr-Y合金晶界弛豫峰向高温处推进。     

Damping behavior and mechanical properties of Mg-Cu-Mn alloy processed by equal channel angular pressing

Equal channel angular pressing(ECAP) was conducted at 250℃for 4 passes to the as-extruded Mg-3%Cu-1%Mn alloy with high strength and high damping capacity.After ECAP processing,the grain of as-extruded alloy is significantly refined to about 4μm,both yield strength and tensile strength of the as-extruded Mg-Cu-Mn alloy are decreased,but the ductility is improved.After the ECAP processing,the damping capacity of Mg-Cu-Mn alloy is decreased at room temperature,while is substantially increased at elevated te...     

Effects of Sn on microstructure of as-cast and as-extruded Mg–9Li alloys

The effects of Sn addition on the microstructure of as-cast and as-extruded Mg–9Li alloys were investigated. The results show that α-Mg, β-Li, Li₂MgSn, and Mg₂Sn are primary phases in the microstructures of the as-cast and as-extruded Mg–9Li–xSn (x=0, 5; in mass fraction, %) alloys. Li₂MgSn phase evolves from continuously net-like structure in the as-cast state to fine granular in the as-extruded state. After the extrusion, Mg–9Li–5Sn alloy has finer microstructures. Li₂MgSn or Mg₂Sn compound can act as the heterogeneous nucleation sites for dynamic recrystallization during the extrusion due to the crystallography matching relationship. Extrusion deformation leads to dynamic recrystallization, which results in the grain refinement and uniform distribution. The as-extruded Mg–9Li–5Sn alloy possesses the lowest grain size of 45.9 μm.     

纳米晶和非晶Mg20-xLaxNi10(x=0-6)贮氢合金的贮氢行为

用快淬技术制备了Mg2Ni型贮氢合金,合金的名义成分为Mg20-xLaxNi10 (x = 0, 2, 4, 6)。用XRD、SEM、HRTEM分析了合金的微观结构。发现不含La的快淬合金中没有非晶相,但含La快淬合金中显示以非晶相为主。当La含量x≤2时,铸态合金的主相为Mg2Ni相,但随着La含量的进一步增加,铸态合金的主相改变为(La,Mg)Ni3+LaMg3相。应用Sieverts设备研究了铸态及快淬态合金的吸放氢量及动力学,结果表明,x=2的合金吸放氢量及动力学随淬速的增加而增加,但对于x=6的合金,结果是相反的。电化学测试结果表明,x=2合金的放电容量随淬速的增加而增加,而对于x=6合金,结果也是相反的。快淬显著地提高了x=2, 6合金的循环稳定性     

Microstructures and Mechanical Properties of Mg-2Y-xZn (x=1, 2, 3 at%) Alloys

研究了Mg-2Y-xZn(x=1,2,3 at%)合金在铸态、退火态和挤压态的显微组织与力学性能。结果表明:随着合金中Zn含量的增加,合金显微组织中第二相依次为18R-LPSO相、(LPSO+W)混合物和W相。在退火过程中,层片状的14H-LPSO结构析出并沿块状18R-LPSO结构向基体中生长,W相由铸态时弯曲的条纹状转变为颗粒状。经过挤压变形后,LPSO结构和W相均沿挤压方向排列,合金性能得到大幅度提高,其中Mg-2Y-1Zn合金具有最好的室温力学性能,抗拉强度为320 MPa,延伸率达到11.2%。     

Mechanical properties and fracture behavior of Mg–2.4Nd–0.6Zn–0.6Zr alloys fabricated by solid recycling process

Mechanical properties of Mg–2.4Nd–0.6Zn–0.6Zr magnesium alloys fabricated by solid recycling process were examined in different conditions, including as-cast, as-extruded and extruded-T6 extruded at 673, 723 and 773 K, respectively. Tensile strength is greatly improved and elongation decreases with the extruding temperature decreasing. The strength of extruded-T6 alloys is higher than that of as-extruded alloys. But the ductility of extruded-T6 alloys is inferior to that of as-extruded alloys. All the extrusions show higher strength and ductility than the ingots. Fracture behavior was analyzed with SEM. Many dimples, cleavage planes and tear ridges were detected in the fracture surfaces, which show obvious mixed-fracture mechanisms.