四元锆基块体金属玻璃

在最近十几年来开发了为数众多的新型多元块体非晶合金，这些合金都具有低的临界冷却速度（～10K／s）和直径大至70mm左右的完全非晶态棒材。新近开发的Zr56Cu22Fe8Al12四元锆基合金具有很好的玻璃形成能力和压缩变形塑性，是一种很有发展前景的非晶态合金，因此日本国立材料科学研究所新近进一步研究了这一非晶态合金的改良效果，通过添加微餐Co和Ag对其性能的影响。研究用的合金是采用高纯度金属锆、铜、银、钴、铁和铝配成的原料，     

定向凝固制备内生晶体增塑的锆基非晶复合材料

通过Bridgman定向凝固成功制备了成分为Zr58.8Ti14.3Nb5.2Cu6.1Ni4.9Be1.0的内生枝晶增塑的非晶复合材料.内生枝晶的尺寸和体积分数可以经抽拉速度的改变得以控制,进而实现了对其力学性能的调节.研究表明,枝晶的大小与抽拉速度呈线性关系,体现出定向凝同在制备非晶复合材料方面可调控析出相的优势.通过对实验参数抽拉速度的优化得出,当抽拉速度为1.0 mm/s时,最高压缩强度达到了1930 MPa,断裂塑性达到11.3%.     

回火Zr-Al-Ni-Cu-Ag块体金属玻璃中的准晶及纳米准晶

通过系统的透射电子显微镜观察,在回火的Zr-Al-Ni-Cu-Ag块体金属玻璃中发现了准晶相和纳米准晶相。具有五次对称性,三次对称性及二次对称性的选区电子衍射谱及微束电子衍射谱证明初始晶化过程中析出的相为二十面体准晶。定量观察表明高的形核率是纳米准晶形成的原因。添加银有助于纳米准晶的形成。二十面体准晶相在初始晶化过程中的析出暗示着块体金属玻璃和二十面体结构之间存在着本征的相关性。     

Sc提高锆基块体非晶合金玻璃形成能力的机理

以Zr52.5Cu17.9Ni14.6Al10Ti5五元锆基非晶合金为研究对象，在以工业级海绵锆为原料制备的合金中加入元素Sc，制备出楔形试样，从微观角度分析了元素Sc提高非晶合金玻璃形成能力的机理。结果表明，元素Sc的加入可显著改变Zr52.5Cu17.9Ni14.6Al10Ti5五元锆基块体非晶态合金在非晶态-晶态过渡区中先析相的相结构及组织形态。元素Sc强烈的脱氧作用可减少合金中锆氧化物／锆氧团簇，从而消除了过冷液体中异质形核的核心，提高了Zr52.5Cu17.9Ni14.6Al10Ti5五元锆基块体非晶态合金的玻璃形成能力。     

含B2-CuZr相CuZr基块体金属玻璃复合材料应变速率敏感性的变化

通过应变速率跳跃模式下的单轴压缩试验,研究了含有不同体积分数B2-CuZr相的CuZr基块体金属玻璃复合材料的应变速率敏感性。研究结果发现,随着B2-CuZr相体积分数的增加,在3.7×10?5 s?1至3.7×10?3 s?1的应变速率范围中,该复合材料的应变速率敏感指数可由负值变化为正值。但是,对于B2-CuZr相体积分数高达约80%的复合材料,其应变速率敏感指数的正值仍然是反常的低。这一现象与B2-CuZr相自身力学行为所呈现的有限应变速率依赖性有关,是由于变形过程中B2-CuZr相的马氏体相变效应所致。研究结果显示,CuZr基块体金属玻璃复合材料的极限应变速率敏感性受制于B2-CuZr相。     

钨丝增强ZrAlNiCuSi块体非晶复合材料及其塑性行为

采用渗流铸造法制备出了钨丝增强ZrAlNiCuSi块体非晶复合材料，在压缩条件下复合材料表现出弹性-完全塑性的应力-应变行为，和未复合的大块非晶相比，总应变量提高600%以上，非晶复合材料塑性提高的原因是钨丝阻碍了非晶基体剪切带的滑移，诱发多个剪切带的产生，同时滑移的面积增大的结果，复合材料的破坏方式与钨丝体积分数有关，在体积分数小于40%时一般为剪切破坏，大于60%时为纵向劈裂破坏，介于（40-60）%之间时，在钨丝与界面结合良好的情况下，趋于剪切破坏，否则为劈裂的破坏方式。     

内生枝晶相体积分数可控的钛基非晶复合材料

采用直接调控增塑相摩尔分数的方法成功制备了系列含有bcc枝晶相的(Ti32.8zr30.2Ni5 3Cu9Be22 7)100-s(Ti61 5-Zr36 4Cu2.1)x(x=10—95)非晶复合材料.采用xRD,SEM和DSC等方法研究了不同x值下枝晶相的体积分数以及形貌的变化规律,并利用TEM研究了内生枝晶相的结构和两相界面结构.结果表明,在Ti32 8Zr30 2Ni5 3Cu9Be22 7合金中直接添加不同量的Ti61 5Zr36.4Cu2.1合金能够有效地控制内生枝晶相的析出量,获得界面结合良好的非晶复合材料,且枝晶相的尺寸及体积分数与x值成正比.室温压缩实验结果表明,当x>30时,复合材料的塑性变形能力可得到明显改善.x值越大,枝晶相体积分数越高,复合材料屈服强度越低,塑性改善效果越明显.不同体积分数的复合材料均表现出明显的加工硬化现象.当x=90时,复合材料的塑性变形量达到14.4%,断裂极限强度达1917 MPa.     

超高强度及塑性的钨丝增强ZrTiCuNiBeNb金属玻璃复合材料

采用渗流铸造工艺制备了钨丝增强ZrTiCuNiBeNb金属玻璃复合材料,利用X射线衍射、扫描电镜、压缩力学试验机研究了复合材料的相组成、界面结构及室温力学性能。结果表明,钨丝增强ZrTiCuNiBeNb金属玻璃复合材料界面非常清晰光洁,证明了微量Nb元素的加入能够有效地抑制界面反应的发生;含钨丝体积分数60%的复合材料具有超高的强度(断裂强度3695MPa)和室温塑性(塑性应变25.3%)。优化的界面结构和钨丝体积分数是产生这种现象的原因。     

氢对锆基块体非晶合金形变和开裂的影响

通过充氢和未充氢缺口拉伸试样和三点弯曲试样在SEM下的原位加载,研究了氢对Zr65Al7．5Ni10Cu17．5块体非晶合金形变和开裂过程的影响,结果表明,无论是否有氢,块体非晶的剪切带发展到临界尺寸,剪切裂纹就沿剪切带形核、扩展,它一旦张开就导致快速的断裂,断口边缘观察到的无特征区是剪切带,而不是剪切裂纹断口;剪切断口形貌和拉伸断口形貌没有本质区别,只有当长时间充氢才能形成氢鼓泡,如鼓泡很小或尚未形成,则氢对剪切带以及裂纹的形核、扩展没有明显影响;如存在较大的氢鼓泡,则当剪切带尚未充分发展时微裂纹就形核,导致低应力脆断。     

合金微结构的调整对铁基块体金属玻璃室温塑性的影响(英文)

报道一种新奇的现象,即随着Fe75Mo5P10C8.3B1.7块体金属玻璃的直径从1.5mm增加到2.0mm,其室温压缩塑性反而从0.5%增加到1.8%。这主要归因于随着铁基块体金属玻璃样品直径的增加,原位形成了零星的α-Fe枝晶相,这种在边缘化的块体金属玻璃中出现的异质结构是提高当前铁基块体金属玻璃室温塑性的主要原因。     

Effect of minor Nb addition on mechanical properties of in-situ Cu-based bulk metallic glass composite

In-situ formed (Cu_0.6Zr_0.3Ti_0.1)₉₅Nb₅ bulk metallic glass (BMG) composite with Nb-rich dendrite randomly dispersed in hard glassy matrix was prepared by casting into a water-cooled copper mold. The dendrite has much smaller hardness and elastic modulus than glassy matrix, and the stress concentration at interface provides a channel for the initiating and branching of shear bands upon loading, thus leading to a high compressive fracture strain of 6.08% and fracture strength about 2200 MPa. Comparing with other Cu-based BMG composite, the fracture strength of present (Cu_0.6Zr_0.3Ti_0.1)₉₅Nb₅ composite is not significantly reduced, indicating that the addition of Nb in the current work is an effective and effortless way to fabricate new practical BMG composites with enhanced strength and good plasticity.     

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。     

Temperature effects on mechanical properties,deformation behavior and formability of Zr−Ti−Cu−Ni−Be−Nb bulk metallic glass composite

The deformation behavior and macroscopic formability of a Zr-based bulk metallic glass composite (BMGC) has been investigated in this study by performing a series of compression and laboratory-scale extrusion tests under various deformation rates within the supercooled liquid temperature region. The morphology of Zr−Ti−Nb-rich dendrite precipitates after warm deformation was first examined by using optical microscopy (OM) and a field emission scanning electron microscope (FE-SEM). The extrusion of this BMGC alloy within the supercooled liquid temperature region was found more difficult than the extrusion of other Zr-based monolithic BMG alloys, possibly due to the existence of dendrite phases hindering the characteristic viscous flow generated in the amorphous phase. A FEM simulation has also been carried out by utilizing the stress-strain behaviors obtained from high temperature compression tests, and the results have been compared with the experimental extrusion test results. The FEM simulation results for the extrusion process as well as a processing map based on a dynamic materials model (DMM) were found to agree relatively well with the actual macroscopic extrusion formability.     

Formation and mechanical properties of bulk Cu-Ti-Zr-Ni metallic glasses with high glass forming ability

Bulk amorphous Cu52.5Ti30Zr11.5Ni6 and Cu53.1Ti31.4Zr9.5Ni6 alloys with a high glass forming ability can be quenched into single amorphous rods with a diameter of 5 mm, and exhibit a high fracture strength of 2 212 MPa and 2 184 MPa under compressive condition, respectively. The stress—strain curves show nearly 2% elastic strain limit, yet display no appreciable macroscopic plastic deformation prior to the catastrophic fracture due to highly localized shear bands. The present work shows clearly evidence of molten droplets besides well-developed vein patterns typical of bulk metallic glasses on the fracture surface, suggesting that localized melting induced by adiabatic heating may occur during the final failure event.     

Zr基块体非晶合金的微塑性成形性能

采用自行研制的微成形系统进行热压缩实验,分别研究成形温度、成形时间和冲头速度等对尺寸为d1 mm×1.5 mm的Zr41.2Ti13.8Cu12.5Ni10Be22.5块体非晶合金(Vit.1)在过冷液相区微塑性成形性能的影响规律。进一步研究了不同坯料尺寸对Vit.1块体非晶合金在过冷液相区超塑性成形性能的影响程度,结果表明流动应力随坯料尺寸的减小而降低。在此基础上,利用闭式模锻方法成形了分度圆直径为d1 mm的微型齿轮,采用SEM观察成形件的表面形貌,结果表明采用微成形方法可以获得尺寸精度较高的Vit.1块体非晶合金微型齿轮。     

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.     

块体非晶合金Zr45Cu48Al7激光焊接过程中晶化行为的研究

非晶合金作为一种异于晶态合金的金属材料,其受焊行为与晶态材料突出的区别在于非晶材料的晶化问题。采用了激光焊接技术连接块体非晶合金Zr45 Cu48Al7,研究了焊接过程中焊缝和热影响区的晶化行为。基于DSC实验结果,推导了块体非晶合金Zr45Cy48Al7晶化转变温度与加热速率立方根的正比关系,并将此结果应用于激光焊接加热过程中,进行了热影响区(HAZ)晶化体积的研究,分析了焊缝凝固后没有形成枝状晶的原因。     

新型铜合金/非晶复合材料的挤压成形特性

基于大块非晶在过冷液相区间具有较好的热塑性成形特点,选择铜基非晶Cu40Zr44Ag8Al8和铜合金,通过挤压成形工艺,制备出一种新型的铜合金/非晶复合材料;在703 K和挤压速度为0.4 mm/min下对该复合材料进行挤压,获得铜合金、非晶复合材料棒材.通过光学金相(OM)、X射线衍射(XRD)、示差扫描量热分析(DSC)和维氏硬度测试(HV)对挤压变形前、后芯部非晶进行形貌观察和结构分析.结果表明:芯部非晶在挤压前期呈不均匀分布,而后分布非常均匀;结合XRD、DSC和硬度的结果分析,在703 K下挤压后,芯部非晶没有发生晶化.