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。     

Tm对锆基块体非晶合金力学性能和腐蚀性能的影响

采用铜模负压吸铸工艺制备了(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_100-xTm_x（x=0~5,原子分数）块体金属玻璃（BMG）合金,研究了Tm对合金力学性能和抗腐蚀性能的影响。结果表明,当Tm含量增加到3%时,其玻璃形成能力（GFA）和压缩塑性显著提高,但过量Tm会降低GFA。x=3时合金的最大过冷液相区宽度为100 K,抗压强度为1669 MPa,塑性应变为21.01%,远高于Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12 BMG的各项性能（67 K、1439 MPa和5.90%）。然而,电化学测试结果表明,x=3时的合金在3.5%（质量分数）NaCl溶液中的耐腐蚀性不佳,且其耐腐蚀性和力学性能随Tm含量的变化趋势与预期不同。可能是由于过量添加稀土元素Tm,容易形成更多的氧化物,导致点蚀加剧。进一步添加Tm可以提高Zr基BMG钝化膜的完整性和耐点蚀性能,但力学性能不理想。     

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.     

玻璃形成能力及稳定性三角形判定准则

根据降温过程的玻璃形成能力（GFA）和升温过程的玻璃稳定性（GS）,构建了以伪四特征参数组合为顶点的判定玻璃形成能力和稳定性的三角形（Tri-FAS）,从而推导出判定GFA&GS的准则：G-FAS=T_g/T_l+T_x/T_l+T_x/T_g（T_x为起始结晶温度;T_l为液体温度;T_g为玻璃化转变温度）,并从降温过程非晶化与晶化之间的竞争关系和准则各组成项对准则的均衡贡献两个方面进行了修订：G-FAS_m=T_g/(1.5T_x)+T_x/T_l+T_x/T_g和G-FAS_m′=T_g/T_l+T_x/T_l+(T_x/T_g)^a (a≈1.5±0.2)。讨论了G-FAS与临界冷却速率R_c、G-FAS与T_xg（T_xg反映了玻璃的过冷液区,T_xg=T_x/T_g）的相关性,分别能够反映GFA和GS。通过大量金属玻璃和其他玻璃形成体从GFA和GS两方面对判定准则的有效性进行了评估,结果显示：该判定准则无论是GFA方面还是GS方面,在不同玻璃形成体系中均可靠有效,具有广泛应用性。提出的Tri-FAS和G-FAS判定准则在玻璃的生产和实际应用过程中具有指导作用。     

过冷液态Zr48Cu36Ag8Al8块体非晶合金的相分离及组织演变

本文通过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Zr₄₈Cu₃₆Ag₈Al₈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703K保温20分钟时,均一的非晶基体相分离成两种非晶合金,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AlZr₂ AlAg₃相。Zr₄₈Cu₃₆Ag₈Al₈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的局部结构转变,相分离以及纳米晶转变,这个过程意味着Zr₄₈Cu₃₆Ag₈Al₈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。     

内生型(Ti0.474Zr0.34Cu0.06Be0.126)100 - x Fe x (x=0, 2)金属玻璃基复合材料的动态力学行为

为了解内生β-Ti相的Zr/Ti基金属玻璃复合材料的动态力学性能和热力学稳定性,采用力学弛豫谱研究了(Ti_0.474Zr_0.34- Cu_0.06Be_0.126)_100-xFe_x（x=0,2）金属玻璃复合材料。通过引入Fe元素,提高了β-Ti相的稳定性。此外,还发现了一个异常的内耗峰,这是由于在亚稳的β-Ti相中析出ω-Ti所引起的。在玻璃化转变温度T_g以下,由于相变和非晶基体部分结晶的耦合效应,2种金属玻璃复合材料的储能模量均表现出异常过冲行为。所得结果为更好地理解内生亚稳β-Ti型金属玻璃复合材料的复杂动态力学弛豫行为提供了借鉴。     

铒元素对锆基合金的非晶形成能力及力学性能的影响

以海绵锆为原料,采用水冷铜坩埚熔炼和铜模吸铸法制备了直径为3 mm、成分为(Zr_0.55Cu_0.3Al_0.1Ni_0.05)_100-xEr_x (x=0,0.5,1,2,3,4,5)的锆基块体合金,通过对比不同铒含量海绵锆基合金的组织结构与性能,研究了铒元素对其非晶形成能力、热稳定性和力学性能的影响。结果表明：以海绵锆为原料时,锆基合金的非晶形成能力和力学性能明显下降。x=0时,无法制备成锆基非晶合金;添加Er元素后,海绵锆基合金的非晶形成能力和力学性能显著提高,具有非晶态结构;x=2时,海绵锆基非晶合金的力学性能最优,抗压强度σ_bc为2142.5 MPa,室温下塑性应变ε_p为10.01%。与高纯锆制备的同直径(Zr_0.55Cu_0.3Al_0.1Ni_0.05)₉₈Er₂非晶合金相比,其抗压强度恢复97.63%,室温塑性恢复69.95%。添加铒元素有利于改善和提高海绵锆基合金的非晶形成能力和力学性能,为低成本制备锆基非晶合金提供一种新思路。     

(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.     

Si元素对Ti-Cu-Zr-Ni基非晶钎料微观组织和性能的影响

采用电弧熔炼和快冷甩带工艺制备了(Ti_0.46Cu_0.14Zr_0.27Ni_0.13)_1-xSi_x非晶钎料,研究了添加一定量的Si对钎料非晶形成能力的影响。结果表明,当Si的含量达到0.5%时钎料的非晶形成能力最强,钎料的润湿面积为3.06 cm₂,过冷液相区宽度(?T_x)?T_x=56 ℃,约化玻璃转变温度(T_rg)T_rg=0.5387,液相线温度为949 ℃。以此非晶合金作为钎料对SiC和TC4进行真空钎焊,所得钎焊接头剪切强度为80 MPa。Si元素的加入显著提高了钎料的非晶形成能力。     

Ti-Cu基合金玻璃形成能力与力学性能

本文基于“二元共晶混合”法设计Ti-Cu-Ni-Zr合金成分,通过水冷铜模铸造法制备出不同直径Ti-Cu-Ni-Zr合金棒。利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、万能试验机和扫描电镜(SEM)研究了Ti-Cu-Ni-Zr合金玻璃形成能力和力学性能。结果表明,Ti-Cu-Ni-Zr合金具有较高的玻璃形成能力,其临界直径可达4 mm;Ti-Cu-Ni-Zr合金玻璃形成能力近似相等,而表征玻璃形成能力的热力学参数过冷液相区ΔT_x,参数γ,约化玻璃转变温度T_rg也近似相等。通过对合金力学性能进行研究,结果表明,Ti_32.3Cu_47.6Ni_7.9Zr_12.2和Ti_31.6Cu_48.2Ni_7.7Zr_12.5大块非晶合金分别具有0.7%和0.2%的塑性,而Ti₃₀Cu_49.5Ni_7.2Zr_13.3和Ti_28.55Cu_50.7Ni_6.75Zr₁₄大块非晶合金断裂机制近似为脆性断裂。Ti-Cu-Ni-Zr大块非晶合金塑性越大,其剪切带数量越多且扩展深度越大,反之亦然。另外,对于塑性材料,当锯齿流变振幅越大时,对应样品表面剪切带扩展深度越明显,当锯齿流变振幅越小时,对应样品表面剪切带扩展深度较浅;近似脆性断裂的锯齿流变对应次剪切带萌生,而对于完全脆性大块非晶合金,在应力-应变曲线上并未发现锯齿流变现象,相应的在样品外表面也并未发现次剪切带。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。