Sn-Bi-In低温无铅钎料的组织和性能

研究了Sn-Bi-In钎料的微观组织、热学特性、润湿性能以及力学性能随合金成分的变化特点。结果表明:Sn-Bi-In钎料的显微组织含有β-Sn相、Bi相以及InBi中间相,Bi含量的减少会导致Bi相和InBi相所占比例降低;钎料DSC曲线中存在3个不同大小的吸热峰,所有合金熔化开始温度在101.3~103.4℃之间,随着Sn含量的增加,钎料的熔程先减小后增大,铺展面积先增大后减小;钎料的显微硬度随着Bi含量的增加而增大,且In的添加使钎料的硬度明显高于Sn-Bi共晶合金;钎料的抗拉强度和断后伸长率随着Bi含量的增大而降低。     

Ag,Cu对Sn-40Bi钎料合金钎焊性能和显微组织的影响

利用DSC,显微硬度仪以及SEM研究了合金元素Ag,Cu对Sn-40Bi钎料合金熔化特性、润湿铺展性、显微硬度以及焊点显微组织的影响。试验结果表明,在试验参数内随着Ag,Cu含量的增加,钎料的熔程减少,润湿铺展面积和维氏硬度增加,焊点中的Bi相得以细化。     

Bi-Sn-In控温易熔合金的设计与性能

在Bi-Sn、Bi-In、Sn-In二元相图的基础上,设计出系列Bi-Sn-In控温易熔合金,并对合金的熔点、相组成和钎焊接头的力学性能进行了研究。结果表明:低铟含量的Bi-Sn-In合金由Bi、-βSn和InBi相组成;随Sn、In含量的增加,易熔合金的相组成向BiIn、BiIn2和γ(InSn4)转化;合金的固相线、液相线随Bi含量或Bi/In的增大而提高,且当Sn含量(质量分数)为17%时合金的液相线最低;易熔合金的硬度随Bi含量或Bi/In的增加而线性增大,但随Sn含量、In含量的增加而降低;提高合金的Sn含量和Bi/In,可使合金钎焊接头的剪切和抗拉强度得到明显的改善;42.6Bi-17.0Sn-40.4In合金的熔点、熔程和钎焊接头的力学性能与50.0Bi-25.0Pb-2.5Sn-12.5Cd伍德合金相当,符合72℃自动灭火洒水喷头感温元件的要求。     

Bi元素对SAC305钎料合金组织和性能的影响

利用金相显微镜和微型拉伸试验机对SAC305-Bi钎料合金的润湿性、组织和力学性能进行了研究。结果表明:SAC305-Bi钎料合金的润湿性随着Bi元素含量的提高而逐渐提高;当Bi元素含量低于0.5wt%时钎料合金的组织几乎不变化,当Bi元素的含量高于0.5wt%时钎料合金的组织粗化,当Bi元素的含量达到4wt%时形成了一种新的共晶相;SAC305-Bi的抗拉强度随着Bi元素含量的提高而逐渐提高,其延伸长度则逐渐降低。     

Ni含量和烧结压力对SPS法制备NiTi合金显微组织及摩擦学性能的影响

采用高能球磨和放电等离子烧结法(SPS)在1000℃制备了NiTi合金,研究了镍含量和烧结压力对NiTi合金致密度、显微组织、显微硬度和摩擦学性能的影响。结果表明：通过高能球磨后,粉末颗粒尺寸减小,随着镍含量增加,Ni相衍射峰向高角度偏移。NiTi合金致密度随着烧结压力增大而增大,在低烧结压力下,合金致密度随着镍含量增加从94.7%降低到84.6%;在高烧结压力下,合金致密度随着镍含量增加表现出先增加后减小的趋势,在镍含量为45%(质量分数,下同)时,合金致密度最低。NiTi合金中主要由NiTi相、NiTi₂相和Ni₃Ti相组成,Ni₃Ti相含量随着镍含量和烧结压力增大而增大,并且镍含量和烧结压力增大会引起Ni₃Ti相晶格畸变。随着镍含量从0%增加到65%时,合金显微硬度先增大后减小,在镍含量为50%时,显微硬度最大。在相同化学成分下,合金显微硬度随着烧结压力增大而增大。增大镍含量和烧结压力会降低NiTi合金磨损率,显著提高合金耐磨性。室温下NiTi合金的磨损机制是磨粒磨损和黏着磨损。     

Co含量对Sn-0.7Cu合金组织演化及力学性能的影响

采用真空感应熔炼工艺制备了Sn-0.7Cu-x Co(x=0.5,1.0,1.5,2.0wt%)合金,分析了Co含量对钎料合金微观组织和力学性能的影响。结果表明,Co的添加增加了Sn-0.7Cu的熔化温度,合金熔点随着Co含量的增加而增大;Co的添加使Sn-0.7Cu合金组织中出现了短棒状或块状的Co Sn2金属间化合物相,其体积分数随着Co含量的增加而增多。随着Co含量的增加,Sn-0.7Cu-x Co合金的显微硬度和抗拉强度增大,但合金的延展性逐渐降低。     

元素Bi及稀土La、Nd对Zn-10Al-5Cu钎料性能的影响

研究了Bi及稀土添加对Zn-10Al-5Cu(mass%)基体合金的润湿性能、显微组织、力学性能的影响。结果表明:钎料合金铺展面积随Bi添加量的增加而增大;铜铝接头抗剪强度随Bi添加量的增加而先增加后降低,得到的Zn-10Al-5Cu-2Bi(mass%)是性能较为优良的钎料。在Zn-10Al-5Cu-2Bi(mass%)钎料中添加稀土La、Nd,钎料的润湿性得到改善,当稀土元素添加量为0.15%时,钎料的润湿性能最佳。随着稀土元素的添加,钎料中大块的黑色共析组织逐渐变小,基体组织得到细化;当稀土元素含量为0.1%时,基体组织最为均匀、细密,晶粒也达到最大程度的细化,铜铝钎焊接头的抗剪强度达到最大。因此稀土La、Nd元素在Zn-10Al-5Cu-2Bi(mass%)中的最佳添加量为0.1%左右。     

Sn对Cu-Sn-Ti钎料显微组织与性能的影响

为揭示Sn调控Cu-Sn-Ti钎料显微组织与力学性能的规律,采用真空非自耗熔炼法制备Cu-Sn-Ti钎料,利用扫描电镜、X射线衍射仪、能谱仪、万能材料试验机等,研究了Sn对Cu-Sn-Ti钎料的显微组织、显微硬度、剪切强度及断口形貌的影响.结果表明,钎料显微组织随Sn含量增加而演变的规律为：枝晶状初生α-Cu基体相+共晶组织+晶间组织→初生α-Cu基体相+共晶组织→共晶组织→初生CuSn₃Ti₅相+粗化共晶组织+α-Cu基体相(富Sn)+Cu₄₁Sn₁₁相+SnTi₃相,其中晶间组织为α-Cu相和CuSn₃Ti₅相的混合组织+少量的(SnTi₃+CuTi相+Cu₃Ti相).随着Sn含量的增加,钎料显微硬度呈先增大后减小的趋势,钎料剪切强度呈逐渐减小的趋势,断口形貌由准解理断裂向解理断裂+准解理断裂的混合形态转变.增加Sn含量促使钎料形成粗化的CuSn₃Ti_5<...     

合金元素对AgCuZn系钎料合金组织与性能的影响

通过向AgCuZn系钎料合金中添加适量的合金元素Sn,Ni,P,研究了不同元素含量的Sn,Ni,P对AgCuZn系无镉钎料组织性能的影响.结果表明,随着Sn元素含量的增加,钎料的润湿铺展性能整体呈上升趋势;P元素的加入可以降低液态钎料与试件间的表面张力,改善钎料的润湿性和流动性.显微组织分析表明,AgCuZn系钎料合金微观组织主要由富Cu相、CuZn化合物相、Cu5.6Sn化合物相、Cu40.5 Sn11化合物相和Ag的析出相组成,AgCuZn钎料合金中加入Sn元素后生成粗大的树枝晶,使钎料脆性增大;钎料合金中加入Ni元素,生成灰黑色的Ni3P化合物相,微观组织细化;P元素的加入生成灰色的Cu3P化合物相.     

自然时效时间对ZnAl15钎料显微组织与力学性能的影响

对自然时效1、3、5、7个月的ZnAl15钎料进行了显微组织和力学性能分析,结果发现,未经时效的ZnAl15钎料组织主要是过饱和α-Al相和过饱和β-Zn相,随时效时间的延长,钎料中过饱和α-Al相和过饱和β-Zn相发生脱溶分解,引起富Al的α相的体积分数增加,而Zn含量较高的β相和α相组成的共析组织的体积分数减少;另外,钎料组织中O含量逐渐增多,钎料晶界产生氧化物,导致晶界模糊、弱化。钎料组织形貌、相组成等随时效时间的增加而发生改变,导致钎料抗拉强度和延伸率下降、显微硬度升高。时效7个月的钎料其抗拉强度降低33%、延伸率降低65%,而显微硬度增加15%。     

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.     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

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.     

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.     

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。     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

Secondary Recrystallization Behaviors of Grain-Oriented 6.5 wt% Silicon Steel Sheets Produced by Rolling and Nitriding Processes

By rolling and nitriding processes, 0.23- to 0.3-mm-thick grain-oriented 6.5 wt% silicon steel sheets were produced. The core losses of grain-oriented 6.5 wt% silicon steel at frequencies ranging from 400 Hz to 20 k Hz were lower than that of the grain-oriented 3 wt% silicon steel with the same thickness by 16.6–35.8%. The secondary recrystallization behavior was investigated by scanning electron microscopy, energy-dispersive spectroscopy, and electron backscattered diffraction. The results show that the secondary recrystallization in high-silicon steel sheets develops more completely as the nitrogen content increases after nitriding, secondary recrystallized grain sizes become larger, and the sharpness of Goss texture increases. Because more {110}116 grains in the subsurface and the central layer of the sheets have a lot of 20°–45° high-energy boundaries in addition to Goss grains, {110}116 can be the main component through selective growth during secondary recrystallization when the inhibitor quantity is not enough and inhibitor intensity is weaker. The increases in nitrogen content can increase the inhibitor intensity and hinder abnormal growth of a mount of {110}116 grains and therefore enhance the sharpness of Goss texture.