过冷液态Zr_(48)Cu_(36)Ag_8Al_8块体非晶合金的相分离及组织演变（英文）

通过X射线衍射(XRD)、差示扫描量热法(DSC)和透射电子显微镜(TEM)研究了退火温度对Zr_(48)Cu_(36)Ag_8Al_8金属玻璃微观结构演化的影响。结果表明,快速凝固获得的样品为典型的非晶态结构。当样品在703 K保温20 min时,均一的非晶基体相分离成2种非晶合金,即,发生相分离。由于相分离结构与非晶基体在等温退火过程是竞争的关系,这个结构很容易向晶化态进行转变,形成AlZr_2和AlAg_3相。Zr_(48)Cu_(36)Ag_8Al_8金属玻璃的微观结构在过冷液相区等温退火过程中经历了局部结构转变,相分离以及纳米晶转变,这个过程意味着Zr_(48)Cu_(36)Ag_8Al_8金属玻璃的微观结构对退火温度十分敏感。此外,相分离的形成可以加速纳米晶的形成。     

Hf对Zr-Al-Ni-Cu金属玻璃弛豫行为的影响

通过测定快淬态和退火态比热与温度的关系,研究了Hf元素对Zr₇₀Al_7.5Ni₈Cu_14.5（70Zr）、Zr₅₅Al₁₀Ni₅Cu₃₀（55Zr）和(Zr_0.75Hf_0.25)₆₅Al_7.5Ni₁₀Cu_17.5（65Zr_0.75Hf_0.25）厘米级金属玻璃焓和硬度弛豫的影响。结果显示：70Zr和55Zr合金的结构弛豫表现为单峰现象,在退火温度（T_a）接近玻璃转变温度（T_g）时出现弛豫峰;而65Zr_0.75Hf_0.25合金的结构弛豫表现为双峰现象,分别在523和648 K（接近T_g）时出现焓弛豫峰。70Zr和55Zr合金在T_g温度附近出现明显的单峰弛豫行为,表明合金在T_g之前的整个温度范围内具有较高的抵抗退火诱导结构弛豫的能力;另一方面,65Zr_0.75Hf_0.25合金在523 K附近出现一个弛豫子峰,可能是由于Zr-Hf原子对的键合性较弱,混合焓接近于零,随后在T_g附近出现明显的主弛豫。65Zr_0.75Hf_0.25和(Zr_0.5Hf_0.5)₆₅Al_7.5Ni₁₀Cu_17.5（65Zr_0.5Hf_0.5）合金的硬度也表现出类似的双峰现象,导致第一峰的T_a与焓弛豫峰的T_a一致。结果表明,满足非晶形成三原则的Zr、Al、Ni和Cu组成的类二十面体中程有序结构在低T_a温度下保持稳定;只有背离非晶形成三原则的65Zr_0.75Hf_0.25和65Zr_0.5Hf_0.5金属玻璃焓弛豫和硬度弛豫出现了双峰,表明形成大块金属玻璃非必要组元的增加将导致合金结构在低温退火过程中的不稳定性。     

EFFECT OF Gd ADDITION ON THE GLASS FORMING ABILITY AND MECHANICAL PROPERTIES IN A Zr–BASED BULK AMORPHOUS ALLOY

适量的Gd掺杂可提高Zr_50.7Cu₂₈Ni₉Al_12.3块体非晶合金的玻璃形成能力, 当Gd元素掺杂量 (原子分数) 为1%时, 即(Zr_50.7Cu₂₈Ni₉Al_12.3)₉₉Gd₁, 柱状非晶合金直径可达16 mm (不掺杂时为14 mm). 稀土Gd掺杂降低了锆基块体非晶合金的断裂强度与塑性 变形能力. 随着Gd含量的增加, 其断裂方式由单一的剪切断裂转变为剪切断裂与破碎断裂的复合形式, 且含Gd元素掺杂的非晶合金断口呈现了脉状纹络与纳米周期性条纹共存的特征.     

多组元替换Zr-Al-Ni-Cu-Ag金属玻璃的热稳定性和晶化行为

为提高金属玻璃的热稳定性并获得大过冷液相区,研究了成分为Zr_65-x(Al_0.21Ni_0.29Cu_0.04Ag_0.46)_35+x（x=0,7.5,15.0,22.5）的金属玻璃,重点分析了组分浓度对合金热稳定性、热诱导沉淀相以及力学性能的影响。结果表明,随着合金组分浓度的增加,非晶漫散射峰的峰位向更高角度偏移,出现了玻璃转变现象。随着玻璃转变温度（T_g）和晶化温度（T_x）增加,液相线温度（T_l）降低,导致T_x和T_g之间的温度差（ΔT_x）减小,约化玻璃转变温度（T_rg）增大。此外,形核激活能（E_x）和长大激活能（E_p1）随着溶质浓度的增加而增加。初晶从四方Zr₂Ni、Zr₂(Cu, Ag)、ZrAg和六方Zr₅Al₃相的组合转变为单一四方ZrAg相,维氏硬度呈现出增加的趋势。通过研究,发现了具有141 K过冷液相区（ΔT_x）和高热稳定性的新型金属玻璃Zr_65-x(Al_0.21Ni_0.29Cu_0.04Ag_0.46)_35+x（x=7.5）,且具有较强的抵抗晶化的特性。本研究采用的多组元替换策略对提高金属玻璃的热稳定性具有重要意义。     

具有高非晶形成能力的高熵合金Cu29Zr32Ti15Al5Ni19

用铜模吸铸法成功地合成了由两个固溶体相构成的高熵合金(HEA) Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉和相同成分的非晶态合金(HE-BMG)。实验结果表明该成分的高熵合金具有高的非晶形成能力。铸态高熵合金Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉的抗压强度为1127MPa。在750℃保温2小时后的Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉高熵合金的硬度仍高达826HV。     

(Zr55All0Ni5Cu30)0.97Ce0.03非晶合金在含Cl-介质中的腐蚀电化学行为研究

  用电化学技术方法研究了Zr₅₅Al_l0Ni₅Cu₃₀和(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金在含Cl^-介质中的腐蚀电化学行为及添加稀土Ce的影响.结果表明：随Cl^-浓度增加,两种非晶合金的腐蚀速度加快;添加稀土Ce后提高合金耐蚀性;随极化电位的提高,两种非晶合金在0.05 mol/L Na₂SO₄及含Cl^-介质中均出现钝化特征,维钝电流密度随Cl^-浓度增加而减小;Zr₅₅Al_l0Ni₅Cu₃₀非晶合金的电化学阻抗谱由单容抗弧组成(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金的交流阻抗谱在Cl^-浓度较低时呈单容抗弧特征,而随Cl^-浓度的增加,单容抗弧变为双容抗弧.     

FRICTION WELDING OF Zr55Al10Ni5Cu30 BULK METALLIC GLASS

采用摩擦焊对Zr₅₅Al₁₀Ni₅Cu₃₀块体金属玻璃进行了焊接, 当焊机主轴转速为4.0×10³---5.0×10³ r/min, 摩擦压力为80---100 MPa, 摩擦时间为0.2---0.4 s, 顶锻压力和保压时间分别为200 MPa和2 s时, 能够成功实施Zr₅₅Al₁₀Ni₅Cu₃₀金属玻璃的焊接. 用SEM, XRD和TEM观察分析未检测到晶化相, 焊缝处金属仍保持非晶状态. 金属玻璃的塑性在玻璃转变点T_g附近随温度变化很大, 在T_g以上具有良好的塑性变形能力, 这是实施摩擦焊焊接的重要基础.     

Ti48Zr20Nb12Cu5Be15 非晶复合材料的内耗行为

对Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅非晶复合材料的室温力学性能以及随温度变化的动态力学性能进行了研究。结果表明,该非晶复合材料的室温拉伸强度约为1350 MPa,断裂应变约为0.13。随着温度的升高,该非晶复合材料的整体状态由弹性转变为粘弹性。在准点缺陷模型框架下,引入了诸如损耗因子、相关系数等相关物理参数,全面分析了该非晶复合材料动态力学行为,并且模型的理论曲线与实验数据拟合程度较好。因此,准点缺陷模型可以很好地描述不同温度下的Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅非晶复合材料的动态力学行为。     

Zr41Ti14Cu12.5Ni10Be22.5非晶棒料摩擦焊接

设计了一种非晶合金摩擦焊装置,以Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5非晶棒料为研究对象,进行了摩擦焊试验.焊接样品经SEM,XRD,维氏硬度、TEM等检测,结果显示焊接界面无明显未熔合,样品仍然保持非晶态,接头硬度总体增大,接头处出现了纳米晶.采用ANSYS软件对非晶合金摩擦焊的温度场进行仿真.结果表明,在摩擦时间t=0.25s时摩擦界面中心温度超过非晶棒料玻璃转变温度,接触面全部进入过冷液相区,应进行顶锻.仿真结果与摩擦焊试验结果基本吻合,有利于指导焊接试验.     

铜基块体非晶合金纳米压痕研究

本文利用三种不同的纳米压痕模式研究了两种铜基大块金属玻璃Cu₅₉Zr₃₆Ti₅和Cu₆₁Zr₃₄Ti₅。分别采用了加载速率控制模式、载荷控制模式和循环加载模式。当加载速率不超过5mN/S时,试样的杨氏模量随加载速率而变。Cu₅₉Zr₃₆Ti₅和Cu₆₁Zr₃₄Ti₅的弹性模量均随峰值载荷和加载速率的增加而降低。但峰值载荷和加载速率对硬度影响不大。循环加载使Cu₅₉Zr₃₆Ti₅产生轻微加工硬化,而Cu₆₁Zr₃₄Ti₅则不显示这样的结果。而且,Cu₆₁Zr₃₄Ti₅的硬度和模量都明显高于Cu₅₉Zr₃₆Ti₅。     

Electron irradiation induced phase transformation in Zr66.7Cu33.3 and Zr66.7Pd33.3 metallic glass

Crystallization and phase selection in Zr_66.7Cu_33.3 and Zr_66.7Pd_33.3 metallic glass during thermal annealing and electron irradiation were examined. During thermal annealing an equilibrium C11_b–Zr₂Cu phase directly precipitated in the amorphous phase of Zr_66.7Cu_33.3 metallic glass while a thermal equilibrium C11_b–Zr₂Pd phase formed after icosahedral quasi-crystalline phase precipitation in Zr_66.7Pd_33.3 metallic glass. The amorphous phase was not stable under electron irradiation and metastable crystalline phases with face-centered cubic-based structure formed in both kinds of metallic glass by electron irradiation induced crystallization. The unique phase selection in electron irradiation induced crystallization is due to a change in the phase stability of crystal, quasi-crystal and amorphous phase under electron irradiation.     

Thermal stability and crystallization kinetics of Cu-Zr-Al-Ag BMGs investigated with isothermal electrical resistance measurement

The thermal stability and crystallization kinetics of the Cu _x Zr_84-x Al₈Ag₈ (x = 42, 40, 38, and 36) bulk metallic glasses (BMGs) were studied by measurement of isothermal electrical-resistance. As the composition becomes richer in Zr, the longer incubation time at the same relative annealing temperature, and the larger local activation energy needed to achieve the same crystallized volume-fraction, indicate improved thermal stability, which resists crystallization. The improved thermal stability is attributed to a denser atomic random-stacking structure and larger negative heat-of-mixing. During isothermal annealing processes, the four BMGs exhibited the same nucleation mechanism, which is a decreasing rate of nucleation over time. However, the crystal growth mechanisms of the four BMGs are different. The crystallization of the Cu₃₆Zr₄₈Al₈Ag₈ and Cu₃₈Zr₄₆Al₈Ag₈ BMGs is interface-controlled growth, contrasting with diffusion-controlled growth for the Cu₄₀Zr₄₄Al₈Ag₈ and Cu₄₂Zr₄₂Al₈Ag₈ alloys. The different growth modes may be caused by fluctuations in composition due to changes in the quantity and distribution of Cu-rich and Ag-rich regions.     

Approach of the spark plasma sintering mechanism in Zr57Cu20Al10Ni8Ti5 metallic glass

Spark plasma sintering (SPS) was used to sinter gas-atomized Zr₅₇Cu₂₀Al₁₀Ni₈Ti₅ amorphous powder. Systematic analyses were performed to study particle size and annealing time effects on the parts structure and properties. Partial devitrification and particles welding were observed and correlated to particle size and thermal conditions. Mechanical testing, through compression and micro-hardness, reveals that the sintered parts show strength similar to a quenched bulk metallic glass and damaging before failure. However, the pulsed current input does not seem the most relevant way to sinter amorphous powders: during the sintering initial stages (when necks are small), excessive over-heating is generated in the vicinity of particles necks, and is responsible for partial devitrification; further current input at large necks leads to complete densification. Effects of the stress, the thermo- and electro-transports on the sintering are evaluated to provide a better understanding of the SPS mechanisms of densification of metallic glasses.     

Influence of Superheat on Microstructure and Mechanical Properties of Ductile Cu47.5Zr47.5Al5 Bulk Metallic Glass-Matrix Composite

Generally bulk metallic glasses (BMGs) posses very less ductility and toughness at room temperature. Over the recent past years to improve up on these properties in many alloy system BMG composites have been developed. It was also reported that Cu_47.5Zr_47.5Al₅ BMG composite shows a very high strength together with an extensive work hardening-like behavior of large ductility around 18%. In this study, the influence of superheat on microstructure and the resulting mechanical properties in Cu_47.5Zr_47.5Al₅ bulk metallic glass-matrix composite alloy has been studied. The Cu_47.5Zr_47.5Al₅ melt solidifies into a composite microstructure consisting of crystalline precipitates embedded in an amorphous matrix. The crystalline phase consists of B2 CuZr (cubic primitive with CsCl structure) with a small amount of monoclinic CuZr martensitic structure embedded in an amorphous matrix. The volume fraction of crystalline phases varies with melting current as well as position along the length of the as-cast rod, depending on the local cooling condition. The volume fraction and the distribution of the crystalline precipitates are heterogeneous in the amorphous matrix. Room temperature uniaxial compression tests revealed high yield strength ranging from 796 to 1900 MPa depending upon the volume fraction of the crystalline phases present. The presence of the dendritic B2 CuZr significantly improved the ductility. The BMG composites show a pronounced plastic strain up to 14% for the higher volume fraction of crystalline phase.     

Fabrication of a Cu36Zr48Al8Ag8 bulk metallic glass sheet by atmosphere-controlled vertical twin roll strip casting

Large-scale fabrication of Cu₃₆Zr₄₈Al₈Ag₈ amorphous alloy sheets having with lengths above 250 mm was performed using atmosphere-controlled twin roll strip casting. By constructing a continuous cooling transformation diagram, the critical cooling rate was determined to be 212.6 K/s. The size and morphology of the crystalline phases within the amorphous matrix, which was Al-rich and Ag-depleted, were confirmed by scanning electron microscopy. The presence of a small volume fraction fine dendritic crystalline phase was necessary for the improved plasticity of the amorphous strip under tensile deformation mode.     

Glass formation and mechanical properties of (Cu50Zr50)100−xAlx (x = 0, 4, 5, 7) bulk metallic glasses

The effect of Al content on the glass formation and mechanical properties was studied for (Cu₅₀Zr₅₀)_100−xAl_x (x = 0, 4, 5, 7) bulk metallic glasses. The crystallization temperatures of fully amorphous Cu₅₀Zr₅₀, Cu₄₈Zr₄₈Al₄, Cu_47.5Zr_47.5Al₅ and Cu_46.5Zr_46.5Al₇ as-cast rods are 724 K, 753 K, 758 K and 782 K, respectively. The mechanical properties were investigated under compression at room temperature. As-cast Cu_46.5Zr_46.5Al₇ shows the highest yield strength (1867 MPa), whereas Cu_47.5Zr_47.5Al₅ shows the largest fracture strain of 11.2%. The fracture surfaces of the compressed samples were investigated by scanning electron microscopy and their morphology has been correlated with the compressive plasticity.     

Laser welding of annealed Zr55Cu30Ni5Al10 bulk metallic glass

Laser welding is one of the promising ways for manufacturing metallic glass products with complicated shape and geometry. In this work we focus on the effect of annealing treatment and welding parameters on laser welding of annealed Zr₅₅Cu₃₀Ni₅Al₁₀ bulk metallic glass as intended and unintended heat treatment occurs in the process. We find that laser welding can produce well welded specimen plates with no obvious welding defects in the joints and high welding speed may lead to better joints. Although higher annealing temperature or longer annealing time leads crystallization, bulk metallic glass material still remains largely amorphous in the heat affected zone. Compared with the welded joint without annealing, the micro-hardness and bending strength are enhanced due to the presence of the nanocrystals occurred in annealed welding joint. Therefore, appropriate annealing treatment with the annealing temperature near the glass transition temperature and annealing time as long as that in hot embossing of BMG parts may play a beneficial role in laser welding of metallic glasses.     

Plasticity improvement of (Cu43Zr48Al9)98Y2 bulk metallic glass composites by dispersed Ta particles

(Cu₄₃Zr₄₈Al₉)₉₈Y₂-based bulk metallic glass composites (BMGCs) with dispersed Ta particles (3vol.%, 6vol.%, 9vol.%) were successfully fabricated through suction casting. The thermal properties, microstructure, and mechanical properties of the BMGCs were systematically investigated. Ta particles are homogeneously dispersed in the amorphous matrix. Ta particle reinforced BMGCs exhibit similar thermal properties and glass-forming ability with the (Cu₄₃Zr₄₈Al₉)₉₈Y₂ base BMG. Compression test results show that the BMGC with 9vol.% Ta particles has superior mechanical performance with up to 15.7% compressive plastic strain, 2,216 MPa yield strength, and 2,260 MPa fracture strength at room temperature. These homogeneously distributed Ta particles act as discrete obstacles in the amorphous matrix, restricting the highly localized shear band. This results in the formation of multiple shear bands around the Ta-rich particles, which lowers the stress concentration, allowing the shear band to propagate further and improve plasticity.