轧制对Mg-3Cu-1Mn合金温度阻尼峰的影响(英文)

经过变形量4.7%的单道次室温轧制变形,Mg-3Cu-1Mn合金的一次温度—阻尼谱出现了3个明显的阻尼峰;在二次温度—阻尼谱中,3个阻尼峰均发生变化,特别是第3阻尼峰P3受到抑制,变得非常不明显。对各阻尼峰峰温处淬火样品进行金相、XRD、EBSD等实验,研究轧制对Mg-3Cu-1Mn合金温度—阻尼峰的影响。结果表明:在一次温度—阻尼谱中的P3峰处出现织构增强、孪晶急剧消失的现象;轧制变形后,3个温度—阻尼峰依次为位错阻尼峰、晶界阻尼峰和孪晶引发的再结晶阻尼峰;另外,随着拉伸孪晶的消失,室温轧制态Mg-3Cu-1Mn合金的应变阻尼性能大幅度恢复,高应变下接近均匀化退火态Mg-3Cu-1Mn的应变阻尼性能。这说明拉伸孪晶对Mg-3Cu-1Mn合金应变阻尼性能有不利的影响。     

热处理对双辊铸轧ZK60镁合金组织及阻尼性能的影响

采用双辊铸轧法制备了ZK60镁合金条带,采用金相显微镜(OM)和动态机械分析仪(DMA)研究了热处理后ZK60镁合金条带的组织和阻尼性能。退火处理后,组织较为均匀。T6处理后组织转变为均匀的等轴晶。在温度-阻尼谱中出现了2个温度阻尼峰,P1峰为弛豫型阻尼峰,其激活能为132 kJ/mol,P2峰为非弛豫型再结晶阻尼峰。T6处理条件下,时效时间为6 h时,呈现典型的位错型应变-阻尼图谱;在其他时效时间下,呈现2种混合位错型的应变-阻尼图谱。T6态双辊铸轧ZK60镁合金的应变-阻尼性能遵循G-L理论。     

不同相组成铸态Mg-xLi-1Al合金的阻尼性能(英文)

采用真空熔炼法制备三种不同相态的Mg-xLi-1Al三元合金,并使用光学显微镜、X射线衍射分析及动态力学分析仪研究其显微组织及阻尼性能。结果表明:由于锂含量的增加,合金的相结构发生转变且出现新的阻尼机制,其中BCC结构的出现使阻尼性能显著提高,同时弹性模量的减小也使临界应变振幅值降低。两相共存状态的合金随温度变化表现出较高的阻尼现象,并在低温与高温区均出现两个较为明显的峰值,其中低温区的P1峰是位错阻尼峰,高温区的P2峰是晶界阻尼峰。     

NbTi-NiTi原位复合材料的约束态相变阻尼

为使记忆合金展现宽温域高阻尼特性,采用熔炼、热锻、轧制等手段制备原位自生的NbTi-NiTi记忆合金复合材料。借助NbTi对NiTi的约束,拓宽NiTi相变温度区间,获得宽温域相变阻尼。采用LMR-1低频力学弛豫谱测试机测试样品内耗。完全相变测试结果表明:材料能在很宽的温度范围内展现高阻尼特性,并随着预变形量的增加,马氏体逆相变阻尼峰的峰温随之升高,峰宽也随之增加;预变形后,样品在第一次加热过程中阻尼峰的峰温较高,且峰较宽,而第二次加热,阻尼峰温和宽度都明显降低;测试中材料的动态模量也伴有相同的变化。不完全相变测试结果表明:内耗曲线出现双阻尼峰,而动态模量曲线出现阶梯式升高现象,且内耗曲线和动态模量曲线都展现出温度记忆效应。     

微量Y对Mg-0.6Zr合金阻尼性能和力学性能的影响

采用动态机械分析仪(DMA)及电子式万能试验机研究了微量Y对Mg-0.6Zr合金阻尼行为和力学性能的影响,分析了合金的阻尼特性随应变振幅及温度变化的机制。结果表明,添加微量Y(0.5wt%)后,其细晶强化和固溶强化作用提高了Mg-0.6Zr合金的抗拉强度、屈服强度和伸长率。同时由于Y的加入,合金晶界数量增多,对位错运动的进一步阻碍作用使合金的应变振幅效应降低,从而降低了其阻尼性能。研究还发现,Mg-0.6Zr合金及Mg-0.6%Zr-0.5%Y分别在65和75℃处出现一个明显的阻尼峰,且当温度分别达到200和250℃时,合金的阻尼性能随温度升高而急剧增加。     

预制件烧结温度对Bi(OH)_(3~-)Al_(18)B_4O_(33w)/Al复合材料阻尼性能的影响

采用化学方法在Al18B4O33晶须表面涂覆Bi(OH)3,对所制备的晶须预制件进行不同温度的烧结,在晶须表面获得不同结构的涂层.利用挤压铸造方法制备相应的纯铝基复合材料.研究了烧结温度对复合材料微观组织和阻尼性能的影响.结果表明:晶须预制件烧结温度对涂覆复合材料界面微观组织和阻尼性能有显著影响,当烧结温度为530及830℃时,2种复合材料中均存在2个阻尼峰(位错阻尼与界面阻尼),后者的阻尼在整个测试温度范围内最高;当预制件烧结温度为1000℃时,复合材料中仅存在一个界面阻尼峰,产生这种现象的原因主要是由于它们的界面状态不同造成的.     

累积叠轧ZK60/Al复合板材的微观组织及性能研究

通过累积叠轧工艺制备出Al/ZK60/Al复合板,采用SEM、TEM、万能拉伸试验机、动态热机械分析仪研究了变形道次对ZK60/Al复合板材的微观组织及性能的影响。结果表明,不同变形道次复合板界面结合良好,无明显颈缩,断裂现象。随道次增加,ZK60/Al复合板的抗拉强度呈现先上升后下降的趋势,ARB-1道次时复合板的抗拉强度为216 MPa,伸长率达到最大值为2.6%。ZK60/Al多层复合板的温度-阻尼谱存在两个明显的内耗峰,即150℃左右的P_1弛豫型阻尼峰,300℃左右的P_2再结晶阻尼峰;ZK60/Al多层复合板材的应变-阻尼谱呈现典型的位错阻尼机理,应变阻尼可以用G-L理论分析。     

纳米金刚石(ND)增强ZK60镁基复合材料压缩变形织构演变规律

使用粉末冶金法及热挤压制备了纳米金刚石(ND)增强ZK60镁基复合材料(ND/ZK60),利用热-力模拟仪Gleeble 3500测试了其在不同变形温度(150、200、300和350℃)和应变速率(1、0.1、0.01和0.001 s~(-1))下的真应力-应变曲线;使用X射线衍射仪(XRD)测试了ND/ZK60镁基复合材料在变形温度为300℃及不同应变速率下的基面织构。结果表明:ND/ZK60镁基复合材料的真应力-应变曲线在不同变形温度和应变速率下发生了4个典型的阶段,且随着变形温度的升高和应变速率的减小,加工硬化现象逐渐减弱。变形温度为300℃时,挤压态的复合材料(0002)基面织构比不同应变速率下的复合材料基面织构强,且基面织构随着应变速率的减小而逐渐减弱。     

固溶时效处理对Mg-4Zn-0.3Zr合金显微组织及阻尼性能的影响

采用光学显微镜、扫描电镜、动态热分析仪和X射线衍射仪研究了固溶时效处理对Mg-4Zn-0.3Zr合金显微组织和阻尼性能的影响。结果表明,铸态合金晶粒尺寸约121μm,晶界粗大且有MgZn、MgZn₂和Mg₇Zn₃相分布;固溶处理后,晶界处的MgZn、MgZn₂和Mg₇Zn₃相基本溶入基体;时效处理后,晶界处有少量的颗粒状MgZn和MgZn₂相析出。在低应变振幅区,铸态合金阻尼性能最好,在高应变振幅区,固溶态阻尼性能最好,固溶+时效态合金阻尼曲线的斜率最大;3种状态合金在低温区的阻尼峰均由晶界阻尼峰和位错阻尼峰叠加构成,固溶态和固溶+时效态合金在高温区的阻尼峰为弛豫型阻尼峰。     

Ultra-Fine Grained Degradable Magnesium for Biomedical Applications

通过对工业纯镁以及ZM21合金的性能测试研究了镁合金在可降解生物医学中的应用,讨论了等径角挤压制备超细晶以及温挤压对材料性能的影响。晶粒细化导致合金材料压缩强度明显提高,强烈的初始变形织构导致粗晶镁合金拉伸强度高于压缩。等径角挤压能够减弱织构的影响,使不同合金塑性流变行为获得改变。材料腐蚀性能主要受化学成分、晶粒大小以及先前变形诱导晶格畸变程度的综合影响。等径角挤压细化晶粒、增大晶格缺陷密度在一定程度上制衡了材料的腐蚀性能。同时弥散分布的第二相粒子的增加对于点蚀发展有着积极的作用。     

Existing form and effect of zirconium in pure Mg,Mg-Yb,and Mg-Zn-Yb alloys

The existing form and grain refining effects of small zirconium addition in pure Mg, Mg-Yb and Mg-Zn binary alloys, and Mg-Zn-Yb ternary alloy (ZK60-Yb) were investigated. The results show that Zr element exists mainly in single and cluster particles of pure α-Zr or Zn-Zr compounds inside grains and at grain boundaries. Only the particles located in the interior of grains can act as the nucleus for α-Mg growth and effectively promote the formation of Fine equiaxed grains. The broken and dispersed Zr-rich particles produced during the hot extrusion process can form nebulous banded structure in which these free particles may act as obstacles to dislocation motion in wrought magnesium alloys.     

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.     

Refining of pure aluminum cast structure by surface pulsed magneto-oscillation

A technique termed surface pulsed magneto-oscillation (SPMO) was developed for refining the solidification structure of metals and alloys. Its working principles are to allow an electropulse to pass through a cookie-like induction coil mounted on the top of a mold to produce pulsed electromagnetic fields (EMFs) which are expected to modify the solidification process and structure of ingots. The experimental results showed that an electropulse flowing in the induction coil can make pure aluminum cast structures transform radically from the columnar to equiaxed grains. In order to examine the origin of equiaxed grains, the steel gauze was applied to the mold to hinder the migration of free grains induced by the pulsed electromagnetic fields. Through comparison of cast structures it was showed that the equiaxed grains should originate from the upper surface of the melt and/or top mold wall. And the forced convection induced by the pulsed magneto-oscillation plays a vital role in the formation of cast structure.     

The formation of randomly textured magnesium alloy sheet through rapid solidification

The rapid solidification of three magnesium-based alloys has been carried out on copper substrates with four tailored surface morphologies. Increasing surface roughness improved the wetting characteristics of the substrates, as did coating with carbon. Of the alloys tested, AZ31 showed inferior wetting behaviour due to the formation of alumina oxides at the interface between the melt and the copper substrate. This behaviour was obviated by the addition of calcium to the melt. The pure magnesium castings all produced a strongly columnar region and showed a weak crystallographic texture. The alloy castings produced weakly columnar regions with an essentially random texture. The alloys cast onto the carbon-coated substrates produced a fully equiaxed microstructure due to the inhibition of heterogeneous nucleation on the substrate surface. It is demonstrated that a randomly textured microstructure with equiaxed grains can be produced through rapid solidification and the implications of this microstructure for the ductility of magnesium sheet is discussed.     

固溶处理对ZK系镁合金力学及阻尼性能的影响

采用光学显微镜、X射线衍射仪、显微硬度计、拉伸试验以及动态热机械分析仪等研究了固溶处理对ZK系（ZK21,ZK40,ZK60）镁合金组织、力学及阻尼性能的影响。结果表明:经固溶处理后,ZK系合金的晶粒尺寸略有长大,第二相溶解、晶格畸变增加。晶界处脆性相的溶解产生的固溶强化效应导致固溶态合金的抗拉强度和显微硬度明显高于铸态。固溶处理后合金的与应变振幅无关阻尼下降、与应变振幅相关阻尼上升,且临界应变振幅明显增大。同一应变振幅下固溶态合金阻尼性能低于铸态;第二临界应变振幅(ε_cr2)增大使固溶态ZK系合金可以在更大应变振幅范围下使用。ZK系镁合金上述阻尼性能的变化可以用Granato-Lücke理论和塑性阻尼理论来解释。      

电磁组合场对镁合金凝固组织的影响

研究了不同电磁组合场对AZ61镁合金凝固组织的影响.结果表明,在静磁场作用下,镁合金的凝固组织为等轴晶,晶界上的结晶相成网状分布;在静磁场与工频交流电组合场作用下,其凝固组织与只施加静磁场时类似,基本为等轴晶,但由于交流电的施加晶粒明显得到细化,晶界上结晶相的网状结构也变得细小;而在镁合金凝固过程中同时施加静磁场和直流电流组合场时,由于组合场产生的熔体内部的定向力作用的结果,凝固组织主要为蔷薇状晶粒,组织得到明显的净化,其晶界上结晶相的网状结构彻底消失,以不连续的薄条状和点状形态分布.     

Effect of lithium on the casting microstructure of Cu-Li alloys

The effect of lithium on the casting microstructure of Cu-Li alloys was studied via the Wild MPS 46 Automatic camera, Deitz Diaplan, and scanning electron microscope. The result shows that trace lithium added to copper coarsens the grains of Cu-Li alloys in eqniaxed crystal area because of the excellent purification effect. With the amount of lithium increasing, the average grain size increases sharply. But when the amount of lithium increases more, the average grain size decreases instead. At the same time, the typical dentritic crystal area of copper is diminished when lithium is added to pure copper.     

直接能量沉积Ti-XV-15Cr(X=20,25,30,35)合金的组织和阻燃性能

使用直接能量沉积技术,以纯Ti、纯V和纯Cr粉末为原料制备一系列Ti-XV-15Cr(X=20,25,30,35)合金。研究了V含量对Ti-XV-15Cr合金的晶粒形貌、显微硬度、弹性模量及阻燃性能的影响。结果表明,Ti-20V-15Cr、Ti-25V-15Cr和Ti-30V-15Cr合金的显微组织由外延生长的柱状晶和顶部细小的等轴晶组成,随着V含量的增加,柱状晶粒的长/宽比逐渐减小。而Ti-35V-15Cr合金的显微组织与Ti-20V-15Cr,Ti-25V-15Cr和Ti-30V-15Cr有很大的不同,除了顶部是细小的等轴晶,几乎全由近等轴晶组成。结合柱状晶向等轴晶转变(CET)模型以及柱状晶层的高度与Z轴抬升量(ΔZ)之间的关系,解释了微观组织的形成机理。Ti-XV-15Cr合金的平均显微硬度随V含量的增加而略有增加,其弹性模量在123.8与137.6 GPa之间。阻燃测试表明,Ti-35V-15Cr合金具有最佳的阻燃性能。     

Microstructures and Formability of the As-Rolled Mg-xZn-0.5Er Alloy Sheets at Room TemperatureEI北大核心CSCD

As lightweight requirements rise in transportation, aerospace, and other industries, magnesium alloys have a great application prospect. However, the low formability capabilities of magnesium alloys lead to a severe limit in applications. At present, there are many reports on the influences of texture and second phases on the formability of magnesium alloys at room temperature. Nevertheless, the dominant factors affecting the formability performance of magnesium alloys at room temperature are not clear. In this study, the development of the microstructures and texture of Mg-xZn-0.5Er (x = 0.5, 2.0, 3.0, 4.0, mass fraction, %) alloy sheets were studied, and the impact of the texture and second phases on the formability of these sheets were also investigated. The findings showed that the increase in Zn addition led to an early and complete dynamic recrystallization (DRX) in Mg-Zn-Er alloys sheets, and these recrystallized grains would expand significantly during subsequent hot rolling processes. These recrystallized grains with a large size were typically elongated and then helped to create a strong basal texture. Thus, it was discovered that the microstructures of these sheets were typically made up of equiaxed and elongated grains. The formability performance of these sheets was strongly related to the size of the second phases and the texture. The formability of the sheets containing microscopic second phases mainly depended on the basal texture, while the formability of the sheets which contained coarse second phases was mostly influenced by the second phases and basal texture. Particularly, when the component of the coarse second was larger, the formability would get more inferior due to the predominant role of the second phase at room temperature.