Microstructure and mechanical properties of Al-Mg-Mn alloy with erbium

The effect of trace element Er on the microstructure and properties of Al-6Mg-0.7Mn-0.1Cr-0.15Ti alloy was investigated. The results show that the ultimate room-temperature and high-temperature strength sof the alloy have not increased obviously with the addition of erbium, but the uniform elongation of alloys decreases from 9% and 27.5% to 5.5% and 22.5%, respectively. The reason is that the addition of Er will first react with Ti, Cr to form Al20Ti2Er, Al8Cr4Er phases. The precipitation strengthening make...     

Microstructure and mechanical properties of 7075 Al alloy based composites with Al2O3 nanoparticles

A new method was used to fabricate 7075 Al alloy based composites with Al₂O₃ nanoparticles to improve the distribution of particles. In this study, nano-sized particles were fed into the molten alloy through the flow of argon gas, then the Al₂O₃/7075 composites were prepared by solid-liquid mixed casting. The results indicated that the composite samples showed fine microstructure and achieved a homogeneous distribution of particles. Also, it was found that relative to the as-cast 7075 alloy, the Al₂O₃/7075 composites exhibited higher mechanical properties, which is due to the effect of uniform distributed Al₂O₃ nanoparticles reinforcement.     

Evolution of second phases and mechanical properties of 7075 Al alloy processed by solution heat treatment

The effects of solution treatment on the evolution of the second phases and mechanical properties of 7075 Al alloy were studied with scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), differential scanning calorimetry (DSC), hardness and tensile tests. The results show that Mg(Zn, Cu, Al)₂ phases gradually dissolve into the matrix, yet the size and morphology of Al₇Cu₂Fe phase exhibit no change with the increase of the solution treatment temperature and time due to its high melting point. When the solution treatment temperature and time continue to increase, the formation of coarse black Mg₂Si particles occurs. Compared to the as-cast alloy, the microhardness, tensile strength, and elongation of the sample under solution heat treatment at 460 °C for 5 h are increased by 55.1%, 40.9% and 109.1%, respectively. This is because the eutectic Mg(Zn, Cu, Al)₂ phases almost completely dissolve and basically no coarse black Mg₂Si particles are formed.     

Mg-2Nd合金的组织与力学性能

在铸钢坩锅中熔炼制备了Mg-2Nd二元镁合金,试样经不同热处理工艺处理后,测试合金的室温拉伸性能,采用光学显微镜（OM）、扫描电镜（SEM）及透射电镜（TEM）观察合金的显微组织,通过X射线衍射法（XRD）和能谱分析（XEDS）及选区电子衍射花样进行合金中的物相鉴别和微观成分分析。结果表明：Mg-2Nd合金的铸态组织由α-Mg基体和呈离异共晶形貌的Mg12Nd相组成;热挤压后,Mg12Nd相沿挤压方向呈纤维或颗粒状分布;挤压过程中发生动态再结晶,合金的抗拉强度（σb）由铸态的148.8 MPa提高到挤压态的210.2 MPa,伸长率（δ）由铸态的2.8%提高到挤压态的19.9%;热挤压和热轧成形的Mg-2Nd合金,直接时效T5（extruded、rolled）处理能产生形变强化和时效硬化双重作用,其中T5（rolled）态合金σb高达276.4 MPa,δ较热轧态提高了64%;T5（rolled）态组织中出现了β′和β沉淀,尺度均在50 nm左右,对合金产生了明显的时效强化作用。     

Microstructures and mechanical properties of a welded CoCrFeMnNi high-entropy alloy

The response of the CoCrFeMnNi high-entropy alloy to weld thermal cycles was investigated to determine its applicability as an engineering structural material. Two processes were used: high-energy-density, low-heat-input electron beam (EB) welding and low-energy-density, high-heat-input gas tungsten arc (GTA) welding. Weldability was determined through comprehensive microstructural and mechanical property characterisation of the welds. The welds did not develop solidification cracking or heat-affected zone cracks. The microstructures in weld fusion zones are similar to that in the as-cast materials, consisting of large columnar grains with dendrite. The dendrite arm spacing and the extent of elemental segregation were less in the welds than in the cast ingot, and also were less pronounced in the EB weld than in the GTA weld. Compositional microsegregation between dendritic cores and interdendritic regions of the welds was insignificant. Both welds exhibited slightly higher yield strengths than the base metal. The EB weld possessed comparable tensile strength and ductility to that of the base metal. In comparison, the GTA weld maintained ～80% of the base metal’s tensile strength and 50% of the ductility.     

Microstructures and mechanical properties ofAZ91D magnesium alloy processed by low pressure die casting

AZ91D alloy components were cast by low pressure die casting （LPDC） process. The mechanical properties of cast components with different microstructural features （shrinkage and distribution of MgtTAlt2 second phase） were investigated under as-east states. Compared with gravity casting, AZ91D with LPDC has much coarser grain size and second phases（Mg17Al12 and Al8Mn5）. The different size and distribution of Mg17All2 phase and shrinkage correspond to different mechanical properties. The ultimate tensile strengths and elongations are mainly decided by the content and distribution of shrinkage porosity, while the yield strengths are determined by the percentage and distribution of Mg17Al12 phase. The more and finer Mg17Al12 phase in the alloy, the relatively higher the yield strengths are. In the alloy without shrinkage, the mechanical properties are mainly determined by the size and distribution of Mg17Al1l2 phase. The finer Mg17Al12 phase, the better the mechanical properties are. Under optimal process, the density and mechanical properties of LPDC AZ91D are improved with fine microstructures.     

2060铝锂合金FSW接头微观组织和力学性能

对2060铝锂铝合金FSW接头性能进行分析,采用光学显微镜、SEM、EBSD等手段对2060铝锂合金的微观组织、拉伸性能、显微硬度、断口形貌、各向异性等性能进行分析.结果表明,最高强度系数为89.9%,最高延伸率为9.44%;FSW接头各向异性不明显;2060铝锂合金主要强化相为Al₂CuLi,并且沿一定晶体学取向分布,对基体有较强的强化作用.在焊核区及热影响区处,析出相溶解,在冷却过程中析出并长大,与基体没有特定的晶体学取向关系,形成粗大的平衡相;由于焊接过程中剧烈的塑性变形与动态再结晶,织构变为弱织构,不存在明显的晶体学取向.     

AlxFeCoNiB0.1高熵合金的微观组织和力学性能研究

采用真空电弧炉熔炼制备了AlxFeCoNiB0.1（x=0.4,0.5,0.8,1.2,1.6 at%）高熵合金,并对其微观组织和力学性能进行测试。随Al含量增加,合金的铸态枝晶由FCC相转变为B2(AlNi)/BCC相。当x=0.4和0.5时,合金的组织由枝晶FCC相和枝晶间组织B2相及(Fe,Co)2B组成;x=0.8时,枝晶由B2相组成,枝晶间由FCC相及(Fe,Co)2B组成;x=1.2时,枝晶间由共晶组织FCC+(Fe,Co)2B组成,BCC呈纳米级颗粒状;x=1.6时,共晶组织消失。随Al含量的增加,抗压拉强度先上升后下降,Al含量为0.8时达到峰值,为2243MPa,适量的Al能提高高熵合金综合力学性能。     

Effects of Er on the microstructure and properties of AZ31 magnesium alloy prepared via the EMS process

The effects of small amounts of the rare-earth element erbium on the microstructure and the mechanical properties of AZ31 magnesium alloy via the electromagnetic stirring(EMS) process have been studied.It has been shown that AZ31-Er alloys are mainly composed of α-Mg solid solution and β-Mg17Al12 phases.When the Er content reaches 0.12 wt.%,the characteristic peaks of Al2Er can be observed.The micro-structure is obviously refined and the tensile strength of the AZ31-based alloy at ambient temperature is significantly improved by contents of 0.03 wt.% Er,especially the elongation(δ=19%).More addition of Er obviously decreases the tensile strength and elongation of the AZ31-based alloy because of the grain coarsening and the reduction of β-Mg17Al12 phases.     

7050-T7451铝合金搅拌摩擦焊接头组织和性能与疲劳断裂

针对7xxx高强铝合金的焊接研究现状,主要从TIG,MIG,激光焊及激光−电弧复合焊4类熔化焊工艺进行了介绍;从焊接缺陷、焊缝成形、接头软化、疲劳性能及耐蚀性等方面详述了7xxx高强铝合金熔化焊过程中存在的问题。对于7xxx高强铝合金的TIG,MIG,激光焊及激光−电弧复合焊,焊接缺陷、焊缝成形质量差及接头中强化相熔解等因素都会导致接头发生软化、耐蚀性变差及疲劳寿命降低;通过优化焊接工艺参数,减少焊接缺陷,改善焊缝成形质量,有利于改善接头的软化、耐蚀性差及疲劳寿命低等问题。选用合适的焊丝（含Ti,Zr元素及Er,Sc稀土元素）使焊缝产生沉淀强化、细晶强化及固溶强化,可改善接头软化的问题;采用适当的焊后热处理,改善强化相的尺寸、形态及分布状态,也可改善接头软化的问题;而采用适当的焊后热处理,还可以改善接头的耐蚀性。

     

Microstructures and mechanical properties of Al-Cu-Mn alloy with La and Sm addition

The effect of single addition of La or Sm on the microstructures and mechanical properties of an Al-Cu-Mn alloy were investigated by microstructure characterization and tensile test.The results show that addition of La or Sm into the Al-Cu-Mn alloy can remarkably increase the density of θ' phase and refine the microstructure,and thus,improves the mechanical properties at room temperature.La addition results in a more considerable increase in the density and refinement of θ' phase than Sm addition.La addition has a more significant contribution on the mechanical properties of the Al-Cu-Mn alloy than Sm addition.in addition,a new phase of Al6Cu6La is formed in the Al-Cu-Mn alloy with La addition.     

Galvanic compatibility of corrosion protective coatings with AA7075 aluminum alloy

The galvanic compatibility of aerospace aluminum alloy AA7075 with cadmium (Cd), zinc (Zn), and zinc–cobalt–iron (Zn–Co–Fe, 32–37%Co and 1%Fe) alloys was investigated. A comparison of open circuit potential [OCP vs. saturated calomel electrode (SCE)] measurements in 0.6 mM NaCl showed that all coatings would act anodically to AA7075 with an exception of Zn–Co–Fe (37%Co + 1%Fe) alloy which was electropositive to AA7075. During the zero resistance ammetry (ZRA) measurement in 0.6 M NaCl electrolyte the coupled OCP and current density were measured during 7 days of immersion and both Zn and Cd acted anodic and thus sacrificial to AA7075. Galvanic coupling of AA7075 with (37%Co + 1%Fe) Zn–Co–Fe alloy resulted in the consequent dissolution of the AA7075 aluminum alloy. In contrast, Zn–Co–Fe (32%Co + 1%Fe) alloy was found to be anodic to AA7075 during the first 26 h of immersion but after dezincification and cobalt enrichment at the surface became cathodic to the AA7075 aluminum alloy. During coupling with Zn, some pitting was also observed on AA7075.     

Microstructures and mechanical properties of hot rolled AZ31 Mg alloy sheets

The microstructures and mechanical properties of hot rolled AZ31 Mg alloy sheets were studied to understand the microstructure evolution during AZ31 Mg alloy hot rolling process. The roller was heated to 180 ℃ with burning hydrogen, and the extruded plates were rolled at 400 ℃ from 10 to 1 mm with a reduction of 30% in thickness per pass. The result shows that there is no side-cracking of these rolled sheets every pass. The extruded microstructures are greatly refined and mechanical properties are improved. The fine grains of about 4μm were obtained of the final 0.9 mm sheets.     

2219-T852铝合金锻件的显微组织与力学性能

采用拉伸力学试验、光学显微镜、扫描电镜以及透射电镜分析手段,研究2219-T852合金锻件的显微组织与力学性能。结果表明：锻件变形比较充分和均匀, θ′强化相细小分布弥散,纵向力学性能满足美国标准的要求,横向和高向的力学性能优于美国标准的要求;锻件的三向力学性能均满足σb≥400 MPa、σ0.2≥300 MPa、δ5≥5%,无明显的各项异性,有利于其在多向承载结构件中的应用。     

Effects of erbium on microstructure and mechanical properties of as-cast Mg-7Zn-3Al alloy

Mg-7Zn-3Al-xEr(x=0.1,0.4,0.7) magnesium alloys were prepared by permanent mould casting.The effects of rare earth element of erbium on the microstructure and mechanical properties of as-cast Mg-7Zn-3Al alloy at both room temperature and elevated temperatures were investigated with optical microscopy,scanning electron microscopy/energy dispersive X-ray spectroscopy,differential scanning calorimetry,and tensile testing.The results show that the quasi-continuous grain boundary networkedτ(Mg_(32)(Al,Zn)_(49)...     

稀土铒(Er)改性6063铝合金铸态微观组织与性能

通过成分设计,铸造出不同稀土Er含量的6063铝合金.采用光学显微镜、扫描电镜(SEM、EDS)、XRD、维氏硬度计等手段研究了稀土Er铝合金铸态微观组织与性能,从理论上分析了Er的作用机理.结果表明,当Er的含量为0.4%时合金的晶粒细化效果最明显,硬度增幅达到最大值,而当含量超过0.4%时,细化效果减弱,硬度值逐渐降低.在6063铝合金熔铸凝固过程中,大部分Er偏聚于合金的晶界处,形成粗大的金属间化合物物Al3,Er相,有强化晶界、阻止晶粒长大作用;小部分Er与Al生成次生金属间化合物,弥散分布于基体中,产生弥散强化作用,并在形核时充当形核剂,从而可细化晶粒.     

Effect of Mn content on microstructure and mechanical properties of modified ZA-27 alloy

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