冷轧复合工艺制备超轻Mg-Li合金复铝板

研究了采用冷轧复合法制备Mg-Li合金复铝板的工艺,得到了适宜的轧制制度与退火热处理参数,结果表明轧制压下率在60%～65%时复合效果最佳.退火时Mg-Li合金内的α相发生了明显的球化转变,300℃退火1 h后Mg-Li合金的再结晶过程基本完成.Mg-Li合金复铝板的密度为1.6～1.7 g/cm3,具有显著的轻质特点、而耐蚀性较单一Mg-Li合金显著提高.     

Ti-6Al-4V板材低温超塑性的研究进展

提高金属材料性能的方法之一是生产平均晶粒尺寸小于1μm的合金,它可使合金的强度提高2～3倍.亚微米晶合金出现超塑性的温度比微米晶合金的低得多.经超塑性成型/扩散结合(SPF/DB)可获得亚微米甚至纳米晶合金.超塑成型前的合金不允许存在各向异性,利用大塑性变形如等通道挤压或多重等温锻造可消除合金内的各向异性.俄罗斯研究人员给出获得各向同性亚微米晶Ti-6Al-4V板材的方法,并研究了板材的室温和高温机械性能及其超塑性.     

FGH96合金热挤压棒材超塑性研究

对热挤压FGH96合金棒材超塑性进行了研究,结果表明:挤压FGH96合金在1050℃和1100℃的变形温度下具有良好的超塑性,在变形温度为1100℃初始应变速率为3.33×10-4s-1进行超塑拉伸时,伸长率可以达到405%,流变应力降低到32MPa。显微组织分析表明,FGH96合金经控制冷却速度的预热处理后,合金中γ′相尺寸及间距较大,能够促进合金在后续变形过程动态再结晶的发生,并阻碍晶粒快速长大。FGH96合金在挤压变形后发生了明显的动态再结晶,但由于再结晶进行的不充分,晶粒内部仍存在大量变形亚结构,这种亚稳态组织在超塑变形过程中通过进一步回复和再结晶,可以获得平均晶粒尺寸为10μm左右的等轴、均匀、稳定的细晶组织,使合金具有良好的超塑性。     

塑性成形方法对镁合金耐蚀性的影响及展望

随着镁合金产业的快速发展,如何通过塑性成形方法提高镁合金的耐蚀性成为了重要课题。镁及其合金因具有低密度、高比强度和较好的回收性等优点而受到广泛关注,然而室温变形能力和耐腐蚀性能差等缺点是其广泛应用的瓶颈。在总结镁合金腐蚀特点及面临问题的基础上,综合分析了国内外塑性成形方法对镁合金腐蚀领域的相关研究,综述了不同加工成形方法在提高镁合金耐蚀性应用方面的进展,从腐蚀机理和工艺参数2个方面进行了讨论。介绍了不同塑性成形方法对镁合金耐蚀性的影响机制,其中包括挤压–ECAP、超声滚压处理、等通道转角挤压、热轧处理、触变成形、板材挤压、板材轧制、交叉轧制、异步轧制和异步交叉轧制、压铸、快速凝固、搅拌摩擦焊、增材制造、喷丸等。从成分分布、析出相等微观角度阐述了影响镁合金腐蚀行为的机制,指出了塑性成形方法在提高镁合金耐蚀行为方面存在的问题,为提高镁合金的耐蚀性提出建议。     

Mg-14Li-1Al超轻镁合金的挤压工艺与力学性能

确定了LA141合金的挤压工艺,并研究了该合金的力学性能,探讨了挤压工艺对合金力学性能的影响.结果表明,合金能够顺利挤压成形,具有优异的塑性变形能力;挤压件的强度和塑性在较宽的挤压温度范围内保持稳定;挤压速度较低时,挤压件塑性较好.     

01420合金的超塑变形行为

对０１４２０合金的形变热处理工艺和超塑性进行了研究。采用新的形变热处理工艺,即“固溶处理后炉冷到３００℃直接轧制、再结晶、人工时效”,得到了晶粒度为８～１０μｍ的细晶材料;对合金的超塑性变形行为进行了研究,获得的超塑延伸率９５０％,ｍ值为０．７８。     

SiC_w/Al 复合材料轧制变形研究(英文)

研究了 SiC_w/Al 复合材料轧制变形。研究结果表明挤压后复合材料的可轧性大为改善,挤压态复合材料应垂直于晶须的取向方向进行轧制;而铸态的复合材料要获得较大的变形量必须交叉轧制。文中详细讨论了变形前后强度和塑性的变化及影响因素,分析了在两种轧制变形方式下,晶须转动和取向及轧制对晶须长径比(l/d)的影响。     

Mg-Li超轻合金的研究与应用

综述了Mg-Li超轻合金的合金系研究、制备新技术及其在结构材料和功能材料领域的研究和应用,指出了存在的问题,并展望了Mg-Li超轻合金的发展前景.     

高Ca/Al比的Mg-Al-Ca合金的超塑性

针对3种高Ca/Al比的Mg-Al-Ca合金(Mg-3.7Al-3.8Ca,Mg-4.4Al-4.5Ca和Mg-4.9Al-5.0Ca)的超塑性行为展开研究,研究结果表明,铸态镁合金具有二次相Al2Ca分布于晶界的枝晶结构。经挤压后,合金的晶粒被细化,二次相也被细化为更小的粒子。这些合金在400℃时表现出很高的伸长率,Mg-4.9Al-5.0Ca在400℃时3.6×10-4 s-1应变速率下获得最大伸长率572%。超塑性流变的变形机制为晶格扩散(DL)控制的晶界滑移(GBS)。对于挤压态Mg-4.9Al-5.0Ca合金,大部分高温稳定相Al2Ca粒子尺寸为80nm,对晶粒长大的抑制作用强烈,在晶界滑移时协调变形,因此在3种合金中Mg-4.9Al-5.0Ca具有最好的超塑性。     

铸锭铝合金Al-Cu-Mg-Ti高应变速率超塑性

采用常规熔铸、热处理、小挤压比挤压及轧制这一低成本并适合于工业化规模应用的路线,研制了一种具有高应变速率超塑性的铸锭铝合金Al-Cu-Mg-Ti.拉伸试验结果表明在温度为793K、初始应变速率为3.16×10-1s-1的拉伸变形条件下,其超塑伸长率为218%,流变应力为32.5MPa.断面及表面形貌SEM分析和初熔行为的DSC分析表明,该合金高应变速率超塑性变形来自于晶界滑动和位错滑移,与液相没有关系.     

Superplasticity of fine-grained magnesium alloys for biomedical applications: A comprehensive review

The superplastic behavior of medical magnesium alloys is reviewed in this overview article. Firstly, the basics of superplasticity and superplastic forming via grain boundary sliding (GBS) as the main deformation mechanism are discussed. Subsequently, the biomedical Mg alloys and their properties are tabulated. Afterwards, the superplasticity of biocompatible Mg-Al, Mg-Zn, Mg-Li, and Mg-RE (rare earth) alloys is critically discussed, where the influence of grain size, hot deformation temperature, and strain rate on the tensile ductility (elongation to failure) is assessed. Moreover, the thermomechanical processing routes (e.g. by dynamic recrystallization (DRX)) and severe plastic deformation (SPD) methods for grain refinement and superplasticity in each alloying system are introduced. The importance of thermal stability (thermostability) of the microstructure against the grain coarsening (grain growth) is emphasized, where the addition of alloying elements for the formation of thermally stable pinning particles and segregation of solutes at grain boundaries are found to be major controlling factors. It is revealed that superplasticity at very high temperatures can be achieved in the presence of stable rare-earth intermetallics. On the other hand, the high-strain-rate superplasticity and low-temperature superplasticity in Mg alloys with great potential for industrial applications are summarized. In this regard, it is shown that the ultrafine-grained (UFG) duplex Mg-Li alloys might show remarkable superplasticity at low temperatures. Finally, the future prospects and distinct research suggestions are summarized. Accordingly, this paper presents the opportunities that superplastic Mg alloys can offer for the biomedical industries.     

镁合金超塑性研究进展

镁合金因其密度小、比性能好、减震性能好、电磁屏蔽性好等优异性能,在航空航天、电子产品、汽车行业等有着良好的应用前景。目前镁合金还没有投入大规模工业化生产,主要原因之一就是镁合金塑性变形能力差,难以成形为复杂形状的部件。超塑性成形为这一问题的解决提供了可能,因此镁合金超塑性的研究受到了广泛重视。综述了近年来国内外Mg-Al系、Mg-Zn系、Mg-Li系和Mg-Gd系镁合金超塑性研究进展,发现不同体系的镁合金经过不同的处理方法,在理想条件下的超塑性伸长率均能达到400%以上,表现出优异的超塑性,最后对今后进一步的发展方向作出了展望。     

Mechanical Behaviour and Microstructure Evolution of Superplastic Mg-8.4 wt pct Li Alloy and Effect of Grain Size and Phase Ratio on Its Elongation

1. IntroductionMg-Li alloy is the lightest alloy among the nonpoisonous metals and alloys. It has the potential for usein aerospace, armored vehicle, automobile and electric industry due to its low density and high specificstiffness. For example, the stiffness of Mg-9 wt pciLi alloy is 3.05E6 m3 much higher than most industrial Al alloy and Ti alloy (2.6E6 m'). In order tochange Mg-Li alloys into specific components with aminimum amount of machining and joining, it is desirable for such al…     

Mg-Li合金研究最新进展及其应用

在简要回顾Mg-Li合金的历史的基础上对该合金的最新进展情况予以全面总结，包括新合金体系的开发、半固态成形技术、快速凝固技术、复合材料的开发以及超塑成形技术等。介绍了该系合金的应用情况，指出了目前存在的问题，指明了下一步工作的方向，并展望了Mg-Li合金的发展前景。     

新型Mg-8Li-5Al-5Ca合金的微观组织、力学及耐腐蚀性能

设计了新型高钙铝比Mg-8Li-5Al-5Ca合金,通过常温拉伸、失重法、pH测定和电化学测试等方法研究了合金的常温力学性能和耐腐蚀性能。采用扫描电镜(SEM)和X射线衍射(XRD)分析了基体和腐蚀产物相结构、合金显微组织以及腐蚀形貌。研究结果表明,这种镁锂合金形成Al2Ca相包围双基体(α-Mg+β-Li)的结构,挤压后基体组织和第二相粒子均明显细化。Mg-8Li-5Al-5Ca合金的耐腐蚀性能优于一般镁锂合金,且随着挤压比的增大进一步提升。该合金的力学性能协调了镁锂合金的优良塑性和高钙铝比镁合金的高强度,拥有较高的抗拉强度(222 MPa)和延伸率(8.3%)。     

B2O3与Mg-Li 合金反应合成复合材料的热力学及动力学研究

通过DTA 及液淬试验, 对B₂O₃与Mg-Li 合金反应合成MgO 颗粒增强Mg-Li 基复合材料的热力学及动力学进行了研究。结果表明,B₂O₃与Mg-Li 合金的反应温度与Mg-Li 合金常规熔炼温度接近, 且反应速度很快, 适于反应合成复合材料的制备。显微组织观察与XRD 分析发现, 反应生成的MgO 颗粒尺寸细小, 形状圆整且分布均匀。     

Superplasticity of Al–Mg–Li alloy prepared by thermomechanical processing

Abstract

Grain refinement of Al–Mg–Li alloys for superplasticity prepared by thermomechanical processing has been a difficult task due to the cracking of these alloys when rolled at low temperatures. Raising the rolling temperature resulted in enhanced rollability of these sheets with no cracks but very coarse grains after recrystallisation. To solve this problem, a cross rolling schedule was developed to hinder fracture and simultaneously provide enough stored energy for following recrystallisaiton coupled by lowering the reheating temperature. Fine, equiaxed grains of ～7 μm was achieved by this new approach and maximum total elongation of about 915% was obtained when deformed at a temperature of 525°C and an initial strain rate of 1×10^?3 s^?1.     

Sn对镁及镁合金显微组织和性能影响的研究现状及展望

合金化元素Sn在镁基体中的固溶度受温度影响比较大,且能够与镁形成高强、高硬、热稳定性好的Mg2Sn金属间化合物,在理论研究和实际应用上引起了人们的广泛关注。基于Mg、Mg-Al-Zn系、Mg-Mn系、Mg-Zn系、Mg-Li系等合金,综述了Sn对纯镁及镁合金微观组织及力学性能的影响,概述了Sn对镁合金的腐蚀、电化学等其他性能的影响。最后展望了Sn在镁合金中的应用前景。     

Superplasticity and grain boundary sliding in rolled AZ91 magnesium alloy at high strain rates

The superplastic deformation characteristics and microstructure evolution of the rolled AZ91 magnesium alloys at temperatures ranging from 623 to 698 K (0.67–0.76 T_m) and at the high strain rates ranging from 10⁻³ to 1 s⁻¹ were investigated with the methods of OM, SEM and TEM. An excellent superplasticity with the maximum elongation to failure of 455% was obtained at 623 K and the strain rate of 10⁻³ s⁻¹ in the rolled AZ91 magnesium alloys and its strain rate sensitivity m is high, up to 0.64. The dominant deformation mechanism in high strain rate superplasticity is still grain boundary sliding (GBS), which was studied systematically in this study. The dislocation creep controlled by grain boundary diffusion was considered the main accommodation mechanism, which was observed in this study.