Y和Ce对AZ91D镁合金显微组织和力学性能的影响

为了开发低成本、高强度、耐高温的新型镁合金,研究了微量Y、Ce对AZ91D镁合金显微组织和力学性能的影响。研究结果表明:Y和Ce复合加入AZ91D镁合金,能明显细化组织晶粒,从而改善合金在室温和高温下的力学性能。当加入0.6%Ce-0.3%Y(质量分数)时,合金晶粒细化效果较好,其室温和高温力学性能比较理想。     

As-cast microstructure,mechanical properties and casting fluidity of ZA84 magnesium alloy containing TiC

The as-cast microstructure, mechanical properties and casting fluidity of ZA84 alloy containing TiC were investigated. The experimental results indicate that adding 0.5wt%TiC to ZA84 alloy can refine the as-cast microstructure, and do not cause the formation of any new phase. After 0.5wt%TiC was added to the ZA84 alloy, the morphology of ternary phases on the grain boundaries changed from coarse quasi-continuous net to fine disconnected net, and the distribution of ternary phases became dispersive and homogeneous. At the same time, the tensile properties of ZA84＋0.5TiC alloy at room temperature were comparable to those of AZ91D alloy, and were higher than those of ZA84 alloy. At 150 ℃, the tensile and creep properties of ZA84＋0.5TiC alloy were also higher than those of ZA84 and AZ91D alloys. In addition, compared with the AZ91D alloy, the casting fluidity of ZA84＋0.5TiC alloy was slightly poor, but better than that of ZA84 alloy. The reason could be related to the effect of TiC on the solidification temperature range of ZA84 alloy.     

钙和碳变质对AZ91D显微组织与性能的影响

镁合金的晶粒细化对于材质的金相组织和力学性能起着决定性作用．本课题通过在AZ91D中加入Ca和C2Cl6晶粒细化剂,分别研究了Ca,C对AZ91D组织以及力学性能的影响．利用熔剂保护法,制备了AZ91D标准拉伸试样,经过T4,T6处理后,采用金相显微镜（Olympus）、扫面电镜（SEM）和能谱分析仪（EDAX）对制备的试样进行了显微组织、断口形貌及成分进行了观察与分析,并测试了抗拉强度和布氏硬度．试验结果表明：经过显微组织和断口形貌观察,加入细化剂后形成Al4C3,有效的抑制了晶粒的长大,使晶粒得到细化,当Ca和C2Cl6复合应用时,使得AZ91D的晶粒细化更加明显,力学性能得到提高,抗拉强度最高达到216N／mm^2,布氏硬度值达到60HB．     

Effects of rare earth elements on the microstructure and properties of magnesium alloy AZ91D

The effects of rare earth elements on the microstructure and properties of Magnesium alloy AZ91D alloy were studied.The different proportion of rare earth elements was added to the AZ91D and the tensile tests were carried out at different temperatures.The experimental results show that at room temperature or at 120℃ the AZ91D‘s decrease with the increasing amount of the rare earth elements.however,the ductility is improved.The influence of 0.14%Sb(mass fraction)on the AZ91D‘s strength is like that of rare earth elements(0.2%-0.4%)(mass fraction).Microstructure graphs demonstrate that appropriate amount of rare earth elements (0.1%-0.2%) can fine AZ91D‘s grain and improve its ductility.     

离心铸造对AZ91镁合金组织及力学性能的影响

为了研究卧式离心铸造工艺对AZ91镁合金力学性能及显微组织的影响,采用卧式离心铸造方法制备外径为400 mm、厚度为20 mm且长度为1 000 mm的AZ91镁合金管材,并对离心铸造态与自然凝固态AZ91镁合金管材的微观组织及力学性能分别进行了观察与测试.结果表明,离心铸造态AZ91镁合金管材的抗拉强度和伸长率分别为158 MPa和3.4%,与自然凝固态管材相比分别提高了20%和89%.离心铸造态镁合金管材的微观组织得到明显细化.与自然凝固态AZ91镁合金管材相比,离心铸造态AZ91镁合金管材在凝固过程中的共晶转变在很大程度上受到抑制,并形成了以α-Mg为主相的组织.卧式离心铸造方法提高了AZ91镁合金的综合力学性能,并使合金的组织得到细化.     

钢丝增强AZ91复合材料的力学性能

为了提高AZ91镁合金的力学性能,采用浸入铸造法制备了体积分数为3.3%的不锈钢纤维增强AZ91复合材料,并在相同条件下对AZ91及其复合材料进行了热挤压处理.采用扫描电镜（SEM）和力学性能试验机分别对铸态和挤压态材料的显微组织、断口和拉伸性能进行了研究.结果表明：铸态AZ91及其复合材料的抗拉强度分别为250和240MPa.然而经过挤压后,钢丝增强AZ91镁合金的屈服强度和抗拉强度分别达到了375和428.6MPa,与挤压态AZ91和铸态AZ91复合材料相比,分别提高了50%、20%和57.6%、78.6%.同时挤压态复合材料的塑性变形量也显著提高.     

Effects of ultrasonic vibration on plastic deformation of AZ31 during the tensile process

An investigation on the plastic behavior of AZ31 magnesium alloy under ultrasonic vibration(with a frequency of 15 kHz and a maximum output of 2 kW) during the process of tension at room temperature was conducted to reveal the volume effect of the vibrated plastic deformation of AZ31.The characteristics of mechanical properties and microstructures of AZ31 under routine and vibrated tensile processes with different amplitudes were compared.It is found that ultrasonic vibration has a remarkable influence on t...     

Microstructural formation of semi-solid AZ91D alloy stirred by electromagnetic field

With the help of an electromagnetic stirring device, alloy melt quenching and EBSD (electron back scatter diffraction)analysis technology, the microstructure of the semi-solid AZ91D magnesium alloy slurry stirred by rotational electromagnetic field under different stirring power conditions has been studied. The results show that the size of primary α-Mg phase is reduced obviously when the solidifying alloy melt is stirred by rotational electromagnetic field, moreover, the primary α-Mg grains are changed to fine rosette grains or spherical grains which are proved to belong to the different grains in three-dimension by the EBSD analysis technology. The results also show that the stirring power is an important processing parameter in the preparation of the semi-solid AZ91D magnesium alloy slurry. The larger the stirring power, the finer the primary α-Mg grains, the less the rosette primary α-Mg grains, and the more the spherical primary α-Mg grains. Theoretical analysis indicates that a stronger flow motion leads to a more even temperature field and solute field and a stronger man-made temperature fluctuation in the alloy melt so that the specially fine rosette and/or spherical primary α-Mg grains are formed in the semi-solid AZ91D magnesium alloy slurry.     

不锈钢丝增强AZ91镁合金复合材料的显微组织及其力学性能

采用渗流铸造法制备了体积分数约为40%、60%、80%的不锈钢丝增强AZ91镁合金复合材料.利用万能试验机对其进行压缩实验;并利用扫描电镜观察复合材料的显微组织以及压缩后的断口形貌.结果表明:不锈钢丝在AZ91镁合金基体中的分布随着其体积分数的增加逐步均匀;不锈钢丝与AZ91镁合金界面润湿性较好.压缩试验表明:复合材料的抗压强度较AZ91镁合金抗压强度明显提高,40%、60%、80%体积分数的复合材料断裂强度分别为371、387、553 MPa;随着不锈钢丝体积分数的增加,材料的破坏方式由剪切破坏转变为劈裂.     

Refinement mechanism of in-situ Al4C3 particles on AZ91 magnesium alloys

The effects of SrCO3 on the microstructure of AZ91 magnesium alloy were investigated by OM, SEM, EDS, XRD and DTA analyses. The results show that AZ91 magnesium alloy with 1.0% SrCO3 addition has the best refining effect at 730 ℃ for 20 min, the average size of the α-Mg grain in AZ91 matrix alloy is reduced from about 91 μm to 58 μm, with reduction of about 36%. Based on the analysis results of EDS, binding energy, and Gibbs free energy, it is evident that the grain is refined because of the generation of A14 C3 particles which can be used as the crystal nucleus of the magnesium alloy when SrCO 3 is added. Owing to the generation of A14C3 in AZ91 magnesium alloy, the grain boundary is pined and the grain growth is inhibited. In the accession to the Al4C3, small subcooling temperature difference leads to the formation of fine grain microstructure in alloy melt. Fine grain microstructure in AZ91 alloy melt with the addition of SrCO3 can be obtained on the condition of lower undercooling temperature according to the DTA analysis results.     

粗镁直接熔炼AZ91D的力学性能及断口分析

为了研究粗镁直接熔炼AZ91D镁合金锭不同位置上的夹杂分布情况,对AZ91D镁合金锭的三个不同取样位置进行了拉伸及冲击试验,通过扫描电子显微镜对拉伸和冲击断口进行了组织形貌上的观察与分析.结果表明:合金锭中间部分的力学性能要明显优于两侧部分,夹杂含量相对于两侧要低; 粗镁直接熔炼的AZ91D镁合金拉伸与冲击断口形貌呈河流状,为脆性断裂.粗镁直接熔炼的合金产生的夹杂物中的主要元素为C、O、Si,并含有少量Fe、K、Ca、S、Cl、Cr等元素; 在夹杂物周围容易出现二次裂纹,夹杂物的数量和种类直接影响着合金的力学性能.     

Sr Microalloying for Refining Grain Size of AZ91D Magnesium Alloy

The grain refining process of an AZ91D Mg alloy by Sr addition was studied and the heterogeneous nucleating particles of α-Mg were investigated by electron probe microanalysis （EPMA）. With 0.6 wt% Sr addition, the mean grain size of AZ91D alloy was refined from 235.4μm to 52.5 μm at the one-half radius of the ingot. The morphology of primary crystal changed from a sixford symmetrical shape to a petallike shape, Mg-Sr-Al-Fe-Mn heterogeneous nucleating particles were observed at the grain centers and Sr solute atoms presented segregation along the grain boundaries. Grain refinement was facilitated by both the Mg-Sr-Al- Fe-Mn nucleating particles and the Sr solute atoms, and the former played a dominate role in the process.     

晶粒大小对AZ31镁合金绝热剪切敏感性的影响

为了研究晶粒尺寸对镁合金绝热剪切敏感性的影响,采用等通道转角挤压(ECAP)技术对AZ31镁合金进行了不同程度的晶粒细化并采用分离式Hopkinson压杆对细化后的AZ31镁合金试样进行了动态剪切试验.采用光学显微镜、扫描电子显微镜、透射电子显微镜和维氏硬度计,分别对冲击压缩后的AZ31镁合金试样进行了组织观察和硬度测试.结果表明,晶粒越小,AZ31镁合金的绝热剪切敏感性越弱.在对绝热剪切带及其周围组织进行维氏硬度测量时发现,剪切带内细小晶粒区的硬度明显高于其周围组织的硬度.     

Effect of RE on the ignition-proof, microstructure and properties of AZ91D magnesium alloy

The magnesium alloy is prone to burn during die-casting, which limits its applications severely, so the effect of adding rare earth （RE） on the ignition-proof of AZ91D Mg alloy is studied. The results indicate that the addition of mischmetal RE elements has a remarkable influence on the ignition-proof property of the magnesium alloy. It is found that the ignition temperature of the magnesium alloy can be greatly raised by adding a proper amount of RE. When the amount is 0.1wt%, the ignition temperature reaches 877℃ which is 206℃ higher than that of AZ91D without RE and the mechanical properties of the alloy are also improved, However, the amount of RE must be properly controlled because too much RE would induce grain coarsening and reduce the mechanical properties.     

T4处理后AZ91镁合金焊接接头组织演变规律

为了明确固溶(T4)处理工艺参数对AZ91镁合金焊接接头组织演变规律的影响,需要进行T4处理优化设计,确定最佳热处理工艺.热处理后分别采用光学显微镜、扫描电子显微镜和拉伸试验机对焊接接头的显微组织和力学性能进行分析.结果表明,T4处理可以改变接头的组织形态,影响第二相β-Mg17Al12的位置,增大晶粒尺寸,特别是粗晶区;较为合理的T4参数可以提高抗拉强度,提高塑性,降低硬度;AZ91镁合金固溶处理的最佳工艺条件为420℃×15 h,抗拉强度为274.28 MPa.     

基于元胞自动机AZ31镁合金固溶处理研究

镁合金具有导热导电性好、电磁屏蔽性能优越、与环境相容性良好等诸多优点。但是镁合金在室温下塑性较差,导致其在轧制过程中易出现裂纹从而影响其质量。为了有效提高其可塑性,在加工前往往需要对其进行固溶处理。基于此,通过金相实验,得到AZ31镁合金管材原始晶粒组织,基于晶粒长大的热力学机制、曲率驱动机制和能量耗散机制,建立元胞自动机模型,针对镁合金建立了三大晶粒演变规则,研究AZ31镁合金在不同温度和不同时间下晶粒演变规律与边数变化情况,最终获得晶粒均匀分布且以六边形为主的微观组织。通过晶粒长大拓扑学分析与晶粒尺寸分布统计,得出晶粒尺寸在不同温度和时间内呈正态分布,其中六边形晶粒最多;在此基础上,建立固溶情况下的晶粒长大数学模型,合理预测并控制AZ31镁合金固溶后的晶粒尺寸和最终性能,分析了晶粒长大动力学,得出镁合金生长指数为0.87,并通过实验验证了元胞自动机模型的正确性和合理性,为研究镁合金在变形过程中的晶粒演变奠定基础。     

退火处理对单道次轧制镁合金薄板组织的影响

变形镁合金因其优越的性能越来越受到国内外研究者的重视。采用单道次轧制的方法轧制出厚度为0.4 mm的AZ31镁合金薄板。对轧制后的薄板在不同温度、不同保温时间下进行退火处理,分析薄板在不同退火条件下的微观组织变化。结果表明:薄板经退火处理后组织变得更加细小均匀,平均晶粒尺寸为5μm。退火温度和保温时间共同影响着薄板的晶粒度,在320℃退火并保温80 min时平均晶粒度最小,仅有4.02μm。     

轧制对AZ31/AZ91焊接接头组织及扩散的影响

为了理解异种镁合金焊接接头显微组织的变化规律,采用TIG焊接方法制备了AZ31/AZ91焊接接头,研究了轧制变形及热处理对AZ31/AZ91焊接接头显微组织及扩散系数的影响.结果表明,随着轧制变形量的增加,AZ31/AZ91熔合区的晶粒细化程度增大,但在随后的420℃×8 h固溶处理过程中,由于再结晶充分,因此晶粒逐渐变大.在420℃×2 h固溶处理过程中,Al的扩散系数随轧制变形量的增加而增大;在420℃×8 h固溶处理条件下,Al的扩散系数随轧制变形量的增加而减小.相同轧制变形量下,Al的扩散系数随着保温时间的增加而减小.     

Characterization of microstructure evolution and mechanical properties of the spray-deposited AZ31 magnesium alloy

The cylindrical billets of a Mg-3Al-1Zn (AZ31) alloy were synthesized by spray deposition processing. The microstruc-ture evolution and mechanical properties of the alloy were investigated. The results reveal that the microstructure of the AZ31 alloy is refined significantly by spray deposition processing. A homogeneous and equiaxial-grain structure with an average grain size of 17 μm is obtained. Further grain refinement with an average grain size of 5 μm is attributed to dynamic recrystallization during e...     

Mechanical properties and microstructure of as-cast and extruded Mg-（Ce, Nd）-Zn-Zr alloys

1INTRODUCTION Thebeneficialinfluenceofrareearth(RE)metalsontheambientandelevatedtemperature mechanicalpropertiesofmagnesiumalloyhaslongbeenrecognized[13].Recently,Yttriumisaddedto Magnesiumalloytoimproveitstensilestrength andcreepresistance,andsuchinvestigationsatheat resistantmagnesiumalloyhaveledtothede velopmentofWE43andWE54alloys[4,5].Al thoughsuchalloysexhibitgoodpropertiesupto573Kthroughcastingandextruding,therelativelyhighcostofYttriumrestrictstheapplicationof suchalloys.Otherr…