大体积超细晶金属材料的剧烈塑性变形法制备技术

介绍了大体积超细晶金属材料的各种常见剧烈塑性变形法制备技术,系统阐述了各种制备技术的基本原理,并分析比较了这些制备技术的优缺点和适用范围,指出了剧烈塑性变形法制备技术的发展方向。     

超细晶材料制备新工艺——挤扭

近年对块体超细晶材料的研究已成为材料科学领域一大热点。挤扭工艺作为一种新兴的大塑性变形细晶材料制备技术,在细化材料显微组织、改善材料力学性能、提高材料成形性等方面发挥了重要作用,具有广阔的工业应用前景。文章重点介绍了挤扭工艺的基本原理及其变形特点,综述了国内外挤扭工艺的研究现状和研究进展,指出了该工艺目前存在的问题,并对其应用前景进行了展望,具有较好的实用参考价值。     

Textures in nanostructured metals processed by severe plastic deformation

This work demonstrates and analyzes the experimental results of the crystallographic texture formation processes in pure metals with a different type of crystal lattice, which were subjected to severe plastic deformation (SPD) applying various techniques such as high pressure torsion (HPT) and equal-channel angular pressing (ECAP). This article is based on a presentation made in “ICOTOM-13: Textures of Materials” held at Seoul National University, Seoul, Korea, August 26–30, 2002, organized by The Korean Institute of Metals and Materials BK21 Division of Materials Education and Research (Seoul National University) and Texture Control Laboratory (Seoul National University).     

Cu基块状非晶晶化过程的微区变形及力学性能

在玻璃转变温度以下选择350、400、475及600 K进行1 h的等温退火,用纳米压痕仪、扫描电镜等研究Cu基块状非晶晶化过程的力学性能及变形。Cu基块状非晶在纳米压头作用下体现弹-塑性变形方式,载荷—位移曲线和压痕周边多重剪切带的特征证明了塑性变形的存在。350 K退火试样具有较大的压痕硬度HV和弹性模量E值及较小的塑性变形量dn值;400 K退火后,HV和E值显著减小,dn值明显增大;475 K退火后,有少量晶体相析出,但合金以非晶的特性为主,HV和E值继续减小,dn值继续增大;600 K退火后,晶体相进一步长大和析出,其固溶强化和弥散强化使合金的HV和E值有所增加,dn值略有减小。对塑性变形机理进行了初步分析。     

SPD制备纳米/超细晶金属材料的成形方法

为了探索SPD法制备纳米/超细晶金属材料的新工艺方法,对ECAP、HP1等经典工艺方法制备纳米/超细晶金属材料的晶粒细化特点进行了分析,结果显示目前SPD工艺存在的问题主要表现在:成形效率低、变形过程中出现疲劳裂纹、制件尺寸小、显微组织不均匀.指出今后SPD的研究应从晶粒细化机理和纳米结构与材料性能的关系等方面展开.     

Effect of Al addition on formation and mechanical properties of Mg-Cu-Gd bulk metallic glass

The effect of partial substitution of Al for Cu on the glass forming ability（GFA） and mechanical properties of Mg65Cu25-xAlxGd10 （x=0, 1, 3 and 5, molar fraction, %） alloys were studied by X-ray diffi-actometry（XRD）, differential scanning calorimetry（DSC） and uniaxial compression test. The result reveals that GFA of the alloys changes slightly with increasing x from 0 to 3, and then abruptly decreases with x increasing up to 5. The plasticity can be greatly improved with appropriate substitution of Cu by A1 （3%, molar fraction） in Mg65Cu25Gd10 bulk metallic glass, and the resultant fracture strength, total strain to failure, and plastic strain are 898 MPa, 2.19% and 0.2%, respectively.     

Effects of rolling condition on the tensile properties of Mg-MM-Sn-Al-Zn alloy

The microstructures and mechanical properties of Mg-2MM-2Sn-1Al-1Zn (ETAZ2211) sheets fabricated under different conditions have been investigated. Two hot-rolling routes following extrusion have been carried out at 300 °C or 400 °C. One method is to roll the extruded strips parallel to the extrusion direction (ED); the other is to roll the extruded strips perpendicular to the extrusion direction (TD). The strength and the elongation-to-fracture of specimens prepared by a combination of extrusion and rolling processes are increased dramatically when compared those of the simply rolled specimens. Especially, the TD alloy sheet rolled at 300 °C exhibits the best combination of strength and ductility, i.e. yield strength of 178.5 MPa, ultimate tensile strength of 239.1 MPa, uniform elongation of 24.4 % and elongation-to-fracture of 37.9 %. Observation of texture reveals that the intensity of (0002) texture is lower for the TD alloy sheets than that for the ED alloy sheets, indicating that the texture intensity is reduced by change of the rolling direction.     

剧烈塑性变形珠光体钢丝退火组织与性能

研究了经剧烈塑性变形制备的珠光体扁钢丝在不同温度退火后的力学性能和组织.结果表明,在低于200℃退火时,由于应变时效的作用,强度和硬度有所增加；退火温度＞200℃时,强度和硬度不断降低.同时,在变形时引入的高应力和退火温度的作用下,片层状渗碳体在200℃以上退火时开始溶解,并随温度的升高,渗碳体溶解的速度加快,最终形成球化组织.     

不同热变形工艺大塑性变形加工超细晶1570C铝合金的组织、强度和超塑性

将Al-5Mg-0.18Mn-0.2Sc-0.08Zr-0.01Fe-0.01Si(质量分数,％)合金铸锭进行多向等温锻造(应变12)或等径角挤压(应变10,325℃),再进行热轧(325℃)和冷轧(20℃),对比研究合金变形后的组织和力学行为.结果表明,对(亚)晶粒尺寸dUFG=2μm的超细晶组织合金进行多向等温锻造...     

Microstructure and mechanical properties of Zr-Cu-Al bulk metallic glasses

Zr49Cu46Al5 and Zr48.5Cu46.5Al5 bulk metallic glasses（BMGs） with diameter of 5 mm were prepared through water-cooled copper mold casting. The phase structures of the two alloys were identified by X-ray diffractometry（XRD）. The thermal stability was examined by differential scanning calorimetry（DSC）. Zr49Cu46Al5 alloy shows a glass transition temperature, Tg, of about 689 K, an crystallization temperature, Tx, of about 736 K. The Zr48.5Cu46.5Al5 alloy shows no obvious exothermic peak. The microstructure of the as-cast alloys was analyzed by transmission electron microscopy（TEM）. The aggregations of CuZr and CuZr2 nanocrystals with grain size of about 20 nm are observed in Zr49Cu46Al5 nanocrystalline composite, while the Zr48.5Cu46,5Al5 alloy containing many CuZr martensite plates is crystallized seriously. Mechanical properties of bulk Zr49Cu46Al5 nanocrystalline composite and Zr48.5Cu46.5Al5 alloy measured by compression tests at room temperature show that the work hardening ability of Zr48.5Cu46.5A15 alloy is larger than that of Zr49Cu46Al5 alloy.     

剧烈塑性变形制备微纳米材料的变形细化机理

对剧烈塑性变形法(SPD)制备微纳米材料变形细化机理进行了总结归纳,着重介绍了位错变形和热机械变形两种机制,详细论述了材料在剧烈塑性变形加工过程中的组织转变特点,同时给出了SPD变形细化机制等研究方向的个人见解。     

铸造效应引发的块体非晶合金压缩脆性(英文)

研究Zr52.5Cu17.9Ni14.6Al10Ti5块体非晶合金由于铸造过程中表面与心部冷却速率差异诱发的表面软化层对其室温压缩行为的影响。通过逐层除去铸造表面软化层,块体非晶试样表现出脆性-韧性转变。在室温压缩时,除去表面软化层的试样呈现大量致密、均匀分布的剪切带和较好的塑性;而未除去表面软化层的试样仅萌生出少量剪切带,且发生灾难性断裂。除去软化层的试样变形后自由体积增加,说明在压缩过程中发生了应变软化。除去软化层的试样组织结构相对均匀,剪切带稳定扩展,断面平滑;而未除去表面软化层的试样则呈现出多样的断面形貌。     

Zr基大块非晶合金的微区变形及力学性能

利用纳米压痕仪、扫描电镜等研究了Zr基大块非晶合金在纳米压痕条件下的变形及力学性能。Zr基大块非晶合金在纳米压头作用下以弹性-塑性方式变形，载荷-位移曲线及压痕周边多重剪切带(堆起或波纹状)的特征证明了塑性变形的存在。冷却速度、第二相及退火等因素影响非晶合金的压痕硬度HV和弹性模量E，冷却速度小的试样或部位(如试样中心)的HV，E值略高；离第二相(W丝)越近，HV，E值越高；退火处理提高非晶的HV，E值，同时退火与第二相还明显改变压痕周边的变形状态及塑性变形量的大小，退火显著减小塑性变形量，使压痕周边凹陷，而第二相使压痕堆起消失。对塑性变形机理进行了初步分析。     

Cast bulk glassy alloys:fabrication,alloy development and properties

Metallic glasses represent an interesting group of materials as they possess outstanding physical, chemical and mechanical properties compared to their crystalline counterparts.Currently, with well designed compositions it is possible to cast liquid alloys into the glassy state at low critical cooling rates from 100 K·s-1 to 1 K·s-1 and in large critical sample sizes up to several centimeters, which significantly enhances the promise for possible applications as advanced engineering materials.This paper reviews the development of (ZrCu)-based bulk metallic glasses with large sizes by copper mold casting and their unique properties.Additionally, the ex-situ and in-situ second phases reinforced BMG composites with large plasticity are also presented.     

富铁Fe-Nd-Al系大块非晶合金的制备及其性能

利用普通的铜模铸造制备了一系列富Fe的Fe-Nd-Al块状非晶合金,采用X射线衍射仪、差示量热扫描仪、振动样品磁场仪和Instron万能材料试验机研究了Fe-Nd-Al块状非晶合金的热稳定性、室温磁性和力学性能。结果表明：Fe50Nd35Al15、Fe45Nd40Al15和Fe42.5Nd42.5Al15块状非晶合金的△Tm（△Tm=Tm-Tx）和晶化开始温度（Tx）与熔点（Tm）的比值分别为106、90和64K及0.88、0.90和0.93;其临界尺寸分别为1.5、3和4mm。此外,随Fe含量的减少,大块非晶的非晶形成能力和硬磁性能提高,但其力学性能有所下降。     

Effects of non-isothermal annealing on microstructure and mechanical properties of severely deformed 2024 aluminum alloy

Microstructure and mechanical properties of AA2024 after severe plastic deformation (SPD) and non-isothermal annealing were investigated. The non-isothermal treatment was carried out on the severely deformed AA2024, and the interaction between restoration and precipitation phenomena was investigated. Differential scanning calorimetry, hardness and shear punch tests illustrate that static recovery and dissolution of GPB zones/Cu–Mg co-clusters occur concurrently through non-isothermal annealing. Scanning electron microscope and electron backscatter diffraction illustrate that non-isothermal annealing of deformed AA2024 up to 250 °C promotes the particle-free regions and also particle stimulated nucleation. Results show that through heating with the rate of 10 °C/min up to 250 °C, the ultimate shear strength and the hardness are maximum due to the presence of S'/S phases which have been detected during non-isothermal differential scanning calorimetry experiment. Also, recrystallization phenomenon occurs in temperature range which includes the dissolution of S'/S phases. The concurrent recrystallization and dissolution of S'/S phase at 380 °C have been verified by differential scanning calorimetry, mechanical properties, and optical microscope.     

模压形变对纯铜组织和性能的影响

采用交叉模压形变法对纯铜进行不同道次的形变处理,研究交叉模压形变对纯铜显微组织和力学性能的影响。研究结果表明:交叉模压形变可以较有效细化纯铜晶粒尺寸,交叉模压10道次后,平均晶粒尺寸减小63%;材料在塑性变形初期(2道次)细化效果最明显,经相同道次交叉模压形变后,晶粒细化效果逐渐减低;交叉模压变形后纯铜试样的显微硬度和抗拉强度均得到显著提高,但是伸长率下降,硬度值和抗拉强度分别提高了96.4%和31.9%,伸长率由66.67%下降至12.25%。     

AgSnO2触头材料的反应合成制备与大塑性变形加工

研究了银氧化锡电触头材料的反应合成制备以及制备的银氧化锡电触头材料在大塑性变形加工条件下的组织均匀化过程。XRD、SEM、TEM和能谱分析结果表明,反应合成制备的银氧化锡电触头材料的显微组织为纳米氧化锡团聚颗粒生长在银基体颗粒的周围形成大基体、小颗粒的环状。通过对反应合成银氧化锡电触头材料在真应变为4和12大塑性变形条件下显微组织的研究,发现经过大塑性变形加工技术能够对银氧化锡电触头材料显微组织起到均匀化和弥散化作用,且真应变为12的AgSnO2触头材料的组织均匀化程度与抗拉强度都好于真应变为4的AgSnO2触头材料的。     

AZ31镁合金晶粒细化方法及机制研究现状

系统介绍了AZ31镁合金晶粒细化方法及机制,综述了6种制备细晶镁合金大塑性变形方法的工艺特点和应用,展示了大塑性变形方法在AZ31镁合金加工中的应用前景。