Nano structure of rapidly quenched Cu–(Zr or Hf) – Ti alloys and their devitrification process

The structure and primary devitrification process of the melt-spun Cu₆₀(Zr or Hf)₃₀Ti₁₀ alloys were investigated. It was confirmed that the compositional segregation in the diameter range of 5–10 nm exists in the as-quenched state. The nanocrystalline particles with cubic structure are observed in the glassy matrix in thehigh-resolution transmission electron microscopy images, of which size is corresponding to the scale of compositional segregation. Small-angle X-ray scattering measurement also indicates the development of nanoscale inhomogeneity with the same size as that of nanocrystalline particles. The nanocrystalline region has high Cu content. In contrast, Zr or Hf and Ti elements are enriched in the glassy region. These results are recognized as the formation of novel structure consisting of the glassy and nanocrystalline phases. It is suggested that the precipitation of bcc CuZr phase as a primary crystallization phase proceeds in the glassy phase remaining the nanocrystalline phase in the Cu–Zr–Ti alloy. Meanwhile, the glassy and nanocrystalline phases are transformed to an orthorhombic Cu₈Hf₃ phase at the initial crystallization stage in the Cu–Hf–Ti alloy. These differences of crystallization process are consistent with the results of thermodynamic and kinetic analyses of the transformation mode.     

Fabrication of Cu rich bulk metallic glass composites via solidification method

Abstract

Cu based bulk metallic glasses and composites with tiny crystalline phases embedded in metallic glass matrix have been successfully fabricated by solidification technique in the present work. The formation of crystalline phases and structure inhomogeneity in bulk metallic glasses was characterised. Al is used as the minor alloying element to partly substitute Cu element in 61Cu–34Zr–5Ti. The results show that quarternary 60Cu–34Zr–5Ti–1Al alloy exhibits monoamorphous feature, and 56Cu–34Zr–5Ti–5Al alloy has a few crystalline peaks superimposed on a broad diffraction peak, suggesting that a composite structure forms in certain solidification conditions. To further identify the microstructure of the as cast rod, all samples were characterised by scanning electron microscopy (SEM). Small size phases are found in 2 mm diameter 56Cu–34Zr–5Ti–5Al rod, which has larger plastic deformation. The composition of those crystalline phases is also investigated. All results indicate that the presence of certain phases in metallic matrix benefits the mechanical properties of the as cast bulk metallic glasses.     

Microstructure formation and electrical resistivity behavior of rapidly solidified Cu-Fe-Zr immiscible alloys

The immiscible Cu-Fe alloy was characterized by a metastable miscibility gap. With the addition element Zr, the miscibility gap can be extended into the Cu-Fe-Zr ternary system. The effect of the atomic ratio of Cu to Fe and Zr content on the behavior of liquid-liquid phase separation was studied. The results show that liquid-liquid phase separation into Cu-rich and Fe-rich liquids took place in the as-quenched Cu-Fe-Zr alloy. A glassy structure with nanoscale phase separation was obtained in the as-quenched(Cu_(0.5) Fe_(0.5))40Zr_(60) alloy sample, exhibiting a homogeneous distribution of glassy Cu-rich nanoparticles in glassy Fe-rich matrix. The microstructural evolution and the competitive mechanism of phase formation in the rapidly solidified Cu-Fe-Zr system were discussed in detail. Moreover, the electrical property of the as-quenched Cu-Fe-Zr alloy samples was examined. It displays an abnormal change of electrical resistivity upon temperature in the nanoscale-phase-separation metallic glass. The crystallization behavior of such metallic glass has been discussed.     

具有大过冷液相温度区间的Cu基大块非晶合金的制备和机械性能

利用铜模铸造方法制备了具有大过冷液相温度区间的Cu-Zr-Ti-Ni系高强度Cu基大块非晶合金,对于Cu55Zr55Ti15Ni5合金,最大直径达5mm.过冷液相区温度范围ΔTx达45.48～70.98 K.Cu基玻璃合金棒表现出非常高的机械性能和明显的塑性,对于Cu50Zr25Ti15Ni10、Cu55Zr25Ti15Ni5和Cu54Zr22Ti18Ni6合金,压缩断裂强度分别达2155MPa、2026MPa和1904MPa,维氏硬度分别达674、678和685.加入Co元素扩大了CuZr-Ti-Ni系合金的ΔTx,Cu50Zr22Ti18Ni6Co4合金的ΔTx高达74.5K.     

Ti-Zr-Be-Cu-Co块体非晶合金在NaCl溶液中的冲刷腐蚀行为

为评价Ti基块体非晶合金的耐蚀性,以期今后在工业生产中的应用,采用失重法研究了Ti35Zr30Be2 4Cu7.5Co3.5块体非晶合金及其对应晶体成分在质量分数6%Na Cl溶液中0.2、0.4、0.6 m/s流速下的冲刷腐蚀行为.利用X射线分析(XRD)、扫描电镜(SEM)研究了Ti35Zr30Be2 4Cu7.5Co3.5块体非晶合金及其对应晶体成分的相结构、微观腐蚀形貌,并利用电化学极化试验测试2种合金冲刷腐蚀后的耐蚀性.结果表明:随着流速的增加,2种合金的腐蚀速度均升高,其中非晶合金出现最大腐蚀速度峰值的时间由无冲刷状态的32 h缩短到流速为0.6 m/s下的10 h,Ti35Zr30Be2 4Cu7.5Co3.5块体非晶合金腐蚀速度较对应晶体成分小;Ti35Zr30Be2 4Cu7.5Co3.5块体非晶合金较对应晶体成分在质量分数6%NaCl溶液中具有更好的耐蚀性.     

Crystalline Precipitate in a Bulk Glass Forming Zr-Based Alloy and Its Effect on Mechanical Properties

Cylindrical and sheet samples of bulk metallic glass with a nominal composition of Zr52.sNi14.6AI10Cu17.9Ti5 (at. pct) were prepared by melt injection casting. The crystalline precipitates formed during the casting were studied by metallographic observations and selected-area electron diffractions. The effect of crystalline precipitates on the mechanical properties were investigatedby tensile and compressive tests at room temperature. Oxygen contents and the sample sizes(or cooling rates) strongly affect the formation of the crystalline precipitates. Overheating thealloy melt up to 200 K above its melting temperature can effectively prevent the formation ofthe crystalline precipitates to get fully glass samples with diameters up to 2 mm for cylindersand thickness uo to 1 mm for sheets even the oxv~ren content is as hi~rher as 0.08 wt Dct.     

Preparation of Cu-based Bulk Metallic Glass Matrix Composites

Cu47Ti34Zr11Ni8 bulk metallic glass （BMG） matrix composites containing in situ formed TiC particles and 5-TiCu dendrite phase were developed by copper mold cast. The thermal stability and microstructure of the composites are investigated. Room temperature compression tests reveal that the composite samples exhibit higher fracture strength and distinct plastic strain of 0.2%-0.5%, comparing with that of the corresponding Cu47Ti34Zr11Ni8 monolithic BMG.     

Formation of nanocrystalline structure during electron irradiation induced crystallization in amorphous Fe-Zr-B alloys

Effect of electron irradiation on the crystallization and phase stability of Fe₈₈Zr₉B₃ and Fe₇₁Zr₉B₂₀ amorphous alloys was examined. Electron irradiation at an accelerated voltage of 2000 kV was performed at room temperature. The Fe₇₁Zr₉B₂₀ alloy showed a wide supercooled liquid region and the ΔT_x value was 71 K, while no glass transition was observed in Fe₈₈Zr₉B₃ alloy. The amorphous phase in Fe–Zr–B alloys was not stable under irradiation and crystallization from the amorphous phase was accelerated by the irradiation. Nanocrystalline structure composed of α-Fe and cubic-Fe₂Zr was formed in Fe₈₈Zr₉B₃ alloy by irradiation induced crystallization, while no nanoscale precipitates of intermetallic compounds were formed during annealing. In Fe₇₁Zr₉B₂₀ alloy, the formation of nanocrystalline precipitates was also confirmed by irradiation induced crystallization, although the formation of nanocrystalline structure had not been realized in high B concentration Fe–Zr–B alloys by annealing. These new results show that electron irradiation is effective in producing a new nanocrystalline structure.     

Nanostructured Composite Materials with Improved Deformation Behavior

The recent progress in the development of nanostructured composites is described for Zr‐base multicomponent alloys as a typical example for such materials. These advanced composite materials are attractive candidates for structural as well as functional applications. The combination of high strength with high elastic strain of fully nanocrystalline and glassy alloys renders them quite unique in comparison to conventional (micro‐)crystalline materials. However, one major drawback for their use in engineering applications is the often limited macroscopic plastic deformability, despite the fact that some of these alloys show perfectly elastic‐plastic deformation behavior. To improve the room temperature ductility of either fully nanocrystalline or amorphous alloys, the concept of developing a heterogeneous microstructure combining a glassy or nanostructured matrix with second‐phase particles with a different length‐scale, has recently been employed. This review describes the composition dependent metastable phase formation in the Zr‐(Ti/Nb)‐Cu‐Ni‐Al alloy system, which in turn alters the mechanical properties of the alloys. We emphasize the possibilities to manipulate such composite microstructures in favor of either strength or ductility, or a combination of both, and also discuss the acquired ability to synthesize such in‐situ high‐strength composite microstructures in bulk form through inexpensive processing routes.     

Investigation of mechanical properties and devitrification of Cu-based bulk glass formers alloyed with noble metals

The mechanical properties, glass-forming ability, supercooled liquid region and devitrification behaviour of the Cu–Zr–Ti–(Pd, Ag, Pt and Au) bulk glass formers were studied by using a mechanical testing machine, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. The bulk glassy alloys of diameter 2 mm were formed in the Cu₅₅Zr₃₀Ti₁₀Pd₅ and Cu₅₅Zr₃₀Ti₁₀Ag₅ alloys while Cu₅₅Zr₃₀Ti₁₀Au₅ bulk alloy showed mixed glassy and crystalline structure. No glassy phase was formed in the Cu₅₅Zr₃₀Ti₁₀Pt₅ bulk alloy whereas the glassy phase was formed in all of the ribbon samples prepared by rapid solidification. The studied alloys except for the Pt-bearing one have slightly increased compressive fracture or yield strength values compared to ternary Cu₆₀Zr₃₀Ti₁₀ glassy alloy. At the same time Pd and Au addition significantly expand the supercooled liquid region of Cu–Zr–Ti glassy alloy and increase Young's modulus. A nanoicosahedral phase is primarily formed in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ glassy alloys in the initial stage of the devitrification process by nucleation and three-dimensional diffusion-controlled growth. Nearly the same quasilattice constant obtained in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ alloys illustrates the same type of the icosahedral phase in these alloys. However, no icosahedral phase was found in the Cu₅₅Zr₃₀Ti₁₀(Ag,Pt)₅ alloys.     

Investigation of mechanical properties and devitrification of Cu-based bulk glass formers alloyed with noble metals

The mechanical properties, glass-forming ability, supercooled liquid region and devitrification behaviour of the Cu–Zr–Ti–(Pd, Ag, Pt and Au) bulk glass formers were studied by using a mechanical testing machine, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. The bulk glassy alloys of diameter 2 mm were formed in the Cu₅₅Zr₃₀Ti₁₀Pd₅ and Cu₅₅Zr₃₀Ti₁₀Ag₅ alloys while Cu₅₅Zr₃₀Ti₁₀Au₅ bulk alloy showed mixed glassy and crystalline structure. No glassy phase was formed in the Cu₅₅Zr₃₀Ti₁₀Pt₅ bulk alloy whereas the glassy phase was formed in all of the ribbon samples prepared by rapid solidification. The studied alloys except for the Pt-bearing one have slightly increased compressive fracture or yield strength values compared to ternary Cu₆₀Zr₃₀Ti₁₀ glassy alloy. At the same time Pd and Au addition significantly expand the supercooled liquid region of Cu–Zr–Ti glassy alloy and increase Young’s modulus. A nanoicosahedral phase is primarily formed in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ glassy alloys in the initial stage of the devitrification process by nucleation and three-dimensional diffusion-controlled growth. Nearly the same quasilattice constant obtained in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ alloys illustrates the same type of the icosahedral phase in these alloys. However, no icosahedral phase was found in the Cu₅₅Zr₃₀Ti₁₀(Ag,Pt)₅ alloys.     

TiC颗粒增强非晶钛合金基复合材料的热稳定性

用单辊铜轮旋注法制备了TiC颗粒增强Ti45Zr5Cu25Ni20Sn5非晶合金基复合材料.发现在Ti45Zr5Cu25Ni20Sn5非晶合金中加入TiC颗粒可以提高合金的热稳定性.     

Ti基金属玻璃复合材料的腐蚀行为

采用水冷铜坩埚悬浮熔炼-铜模吸铸法制备了直径为3mm的(Ti0.5Ni0.5)80Cu20金属玻璃复合材料试样,对合金的组织结构进行表征,用电化学工作站三电极体系测试了不同腐蚀介质中的动电位极化曲线,并分析表征电化学腐蚀后的形貌和腐蚀产物。结果表明:合金组织由非晶基体+形状记忆晶体相组成,在铸造过程的温度梯度下呈现梯度组织,边缘为快冷形成的无序密堆非晶结构,心部主要析出相为过冷奥氏体相。在人工海水和模拟人体的PBS溶液中,合金均表现出良好的耐蚀性。与晶态TC4合金相比,自腐蚀电位高,腐蚀的热力学倾向小;自腐蚀电流密度低,极化电阻高,腐蚀的动力学速率低。合金在PBS溶液中由于介质中活性阴离子浓度低,比在人工海水中表现出更优异的抗蚀性。在腐蚀形貌中未发现点蚀坑,边缘区的氧化膜较心部区域更为致密均匀。     

Effect of SEM electron beam on the hydrogen desorption of pre-charged amorphous Cu33Ti67 alloys

The crystallization and hydrogen desorption of pre-charged amorphous Cu₃₃Ti₆₇ alloy have been studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and scanning electron microscopy (SEM). The effect of the SEM electron beam on the desorption process was analyzed. It was found that small amounts of absorbed hydrogen do not influence on the thermal stability of the glass, but significantly reduce its crystallization enthalpy. At higher hydrogen concentrations the thermal stability of the glass was strongly reduced (with about 250 K), as the low-temperature crystallization product was mainly extremely fine nanocrystalline Cu₂Ti, formed as a result of the Cu enrichment of the amorphous phase after hydriding. Combining DSC, TG and SEM it was proved that during the electron beam exposure the weaker bonded hydrogen, which desorbs thermally at 430–500 K, releases. Annealing at higher temperatures (> 500 K) showed clearly the existence of nanocrystalline Cu₂Ti and TiH₂ phases. Only after the TiH₂ decomposition (at ~ 680 K) the equilibrium crystalline phase (Ti₂Cu) was formed, but with finer microstructure.     

晶体形态对金属涂层阻尼特性的影响

研究了金属涂层阻尼性能的微观机理。采用磁控溅射技术在不锈钢表面制备了Al、Ti、TiAl合金涂层,利用X射线衍射仪、扫描电子显微镜和能谱分析仪研究了金属涂层的物相、微观结构和元素组成;利用动态热机械分析仪(DMA)分析了涂层的阻尼性能。结果表明:单靶磁控溅射制备Al涂层为典型的片状晶体结构,而Ti涂层为柱状微晶结构;双靶共溅射制备的TiAl合金涂层为Al晶体为核心包裹微晶Ti的合金微团结构。在金属涂层和基体结构阻尼性能测试实验中,频率为31~35 Hz区间Al、Ti、TiAl合金和不锈钢基体四种试样均出现阻尼品质因子倒数(Q^-1)峰;然而在频率为57 Hz时, Al、Ti及TiAl合金涂层的试件出现明显Q^-1峰,其峰值约为0.016,未镀膜的不锈钢基体试样未出现峰值;在57 Hz频率下的应变幅与Q^-1关系曲线中,微团状晶态TiAl合金涂层阻尼性能最强,柱状晶态Ti涂层阻尼性次之、相对而言片状晶态Al涂层最弱。由此可见,晶体结构对金属涂层的阻尼性能的影响存在直接相关性,乱序晶体结构弛豫和晶界纳米缝隙的内摩擦是金属涂层产生阻尼的主要原因。     

W丝增强块状非晶基复合材料单轴压缩形变的研究

利用扫描电子显微镜和透射电子显微镜，研究了室温单轴压缩下W丝增强块状非晶基复合材料的形变特征，结果表明：非晶基体内产生了大量的剪切带，剪切带分布特征与W丝密切相关；非晶基体的微观结构发生了改变，局域内自由体积显著增加。     

含Be多元合金非晶形成能力的替代效应研究

利用晶胞平移和分子动力学模拟建立了Zr4lTil3.8Be22.5Ni17.5Cu5．2晶态和非晶合金的原子结构模型，利用递归方法研究了Zr4lTi13.8Be22．5Ni17．5Cu5．2晶态及非晶态合金中元素的替代效应．Be与B、Al、Si状态密度形状相似表明Be与B、Al、Si具有相似的性质，可以用Al、B、Si代替Be；非晶态相对于晶态的结构能差表明，用Al、B、Si代替Be后均使合金的非晶形成能力下降，只是Al、B下降的幅度较小；用Al、B替代Be，再用其它过渡金属替代Cu、Ni或zr、Ti可使非晶形成能力达到含Be合金的水平．     

Cu-10Cr-0.4Zr原位复合材料的微观组织与性能

制备了Cu-10Cr和Cu-10Cr-0.4Zr合金,并经冷变形形成了原位复合材料,观察了Zr的添加对合金铸态组织、复合材料的纤维形貌,研究了Zr的添加和冷变形率对拉伸强度以及导电率的影响.研究表明,在Cu-10Cr合金中添加的0.4%Zr,Cr析出相的直径由15～80μm细化到10～20μm;在相同的冷拔应变下,Cu-10Cr-0.4Zr复合材料较Cu-10Cr材料具有了更高的基体晶格阻力、更加细小均匀的纤维相以及纤维间距,使得Cu-10Cr-0.4Zr复合材料的强度更高.当冷拔应变达到6.2时,Cu-10Cr-0.4Zr原位复合材料抗拉强度高达1089MPa,而Cu-10Cr材料的抗拉强度仅为887MPa.在相同冷拔应变下,Cu-10Cr材料的导电率比Cu-10Cr-0.4Zr材料中的导电率略高.随着材料冷拔应变的增加,决定复合材料电阻率的基体材料内位错散射电阻转变成界面散射电阻,复合材料的电导率逐渐下降.     

三相(Ti, Zr)N复合陶瓷的物相分析

通过对高纯TiZr合金的高温氮化和高温退火制取了三相(Ti,Zr)N复合陶瓷。此结果不同于TiN与ZrN仅形成单相FCC结构无限固溶体的早期研究。应用X射线衍射(XRD)、X射线能量散射(EDS)及高分辨电子显微术(HRTEM)等技术手段分析研究了该(Ti,Zr)N复合陶瓷的晶体结构和化学成份。X射线衍射分析研究确定了材料的相组成(三相,FCC结构)及三相的晶格常数。微区化学成份分析给出各相中Ti与Zr的相对原子百分含量以及它们的金属元素含量的近似化学表达式。结合高分辨像的研究,最终确定出晶格常数最大的相富Zr,晶格常数居中的相Ti与Zr含量近似相等,而晶格常数最小的相富Ti.     

Zr含量对铸造AlSi7Mg0.4合金力学性能的影响

研究了添加Zr元素的重力铸造AlSi7Mg0.4合金的微观组织和力学性能.结果 表明,在含Zr的铸态合金中生成了(Al,Si)3(Zr,Ti)和π-Fe相,Zr的添加使合金的晶粒尺寸减小;经过T6热处理后富Fe相中的Mg和少量粗大的(Al,Si)3(Zr,Ti)相重溶到基体中,减小了金属间化合物的尺寸,生成了与基体有共...