SP700/TC4钛合金蜂窝夹层结构钎焊工艺分析

采用非晶态Ti-Zr-Cu-Ni箔带钎料对SP700/TC4钛合金蜂窝结构进行钎焊工艺研究,分析了钎焊温度和保温时间对钎焊接头组织和力学性能的影响. 结果表明,当钎焊温度在875～890 ℃之间变化时,随温度升高,钎焊接头中元素扩散更为充分,接头拉脱强度持续增长;在890 ℃下保温2～4 h不同时长进行钎焊,接头的拉脱强度先逐渐增加,在保温时间为3.5 h时达到最大值,随后逐渐降低. 获得SP700/TC4钛合金蜂窝结构的较优钎焊工艺为890 ℃/3.5 h,该工艺下钎焊接头的室温拉脱强度、三点弯曲强度、平面压缩强度、L及W方向抗剪强度分别达到14.64,224.05,11.21,4.43及3.76 MPa,破坏部位均为TC4蜂窝芯.     

Cr对Ni-P系钎料钎焊不锈钢接头性能的影响

研究了钎焊温度对Ni-P系钎料铺展件能及其真空钎焊OCr13不锈钢接头力学性能的影响.结果表明,Ni-P系钎料铺展面积随钎焊温度的升高而增大,并且相同温度下不含Cr的Ni-P钎料铺展面积大于Ni-Cr-P的铺展面积;钎焊温度从925℃升高到1000℃过程中,Ni-P、Ni-Cr-P钎料钎焊不锈钢接头的室温剪切强度均增大,并且在相同钎焊工艺下,不含Cr的Ni-P钎料钎焊不锈钢接头室温剪切强度优于Ni-Cr-P钎焊接头强度30～40MPa;Ni-P系钎料钎焊接头高温强度随温度升高而下降,测试温度超过500℃时,相同温度下含Cr的钎料能够提高钎焊接头强度0～30 MPa.     

铝蜂窝板的自反应钎焊工艺与性能

在不添加钎料的情况下,使用添加4%ZnCl_2和4%SnCl_2(质量分数)的中温CsF-AlF_3自反应钎剂,对成型法制备的铝蜂窝芯及面板进行自反应钎焊连接。通过调整钎焊温度、保温时间等参数,确定铝蜂窝板的自反应钎焊工艺。使用光学显微镜和扫描电子显微镜及能谱仪对钎焊接头进行组织观察和成分与缺陷分析,测试钎焊接头在不同试验温度下的拉剪强度以及蜂窝板的平压强度。结果表明:钎焊温度为570℃、保温时间30 min时,可制备出整体的铝蜂窝板,且钎焊接头连接良好,未出现溶蚀缺陷;蜂窝芯接头的拉剪强度为46~52 MPa,在25~150℃范围内,拉剪强度无明显下降,自反应钎焊制备的铝蜂窝板平压强度可达1.75 MPa。     

采用BNi7钎料钎焊不锈钢接头的组织和性能

研究了BNi7钎料真空钎焊OCr13不锈钢过程中,钎焊温度和时间对钎焊接头组织和室温及高温性能的影响.结果表明:接头组织由钎缝近母材区的Ni-Fe基固溶体和钎缝中间连续的Ni(Cr,Fe)-P化合物组成.随钎焊温度和时间的增加,钎缝中Nj(Cr,Fe)-P化合物含量逐渐减少,Ni-Fe基固溶体含量相应增多,钎缝强度随之而提高.钎缝高温强度在600℃以下随测试温度的升高而逐渐降低,当测试温度高于600℃时,钎缝强度明显下降.     

TC4钛合金蜂窝板钎焊接头组织性能分析

研究了TC4钛合金蜂窝板的钎焊工艺,试验采用Ti-Zr-Ni-Cu钎料,真空度不低于2×10-3 Pa,钎焊温度为930℃,保温时间为30 min.对焊后试件的钎焊界面组织进行超声无损检测,检测结果表明面板与蜂窝芯钎焊效果极好,未发现有脱焊、虚焊等现象.采用扫描电镜（SEM）和能谱分析（EDS）法进行了试验分析.结果表明,母材和钎料发生相互扩散渗透反应,并出现有新的析出相.该工艺下蜂窝板的界面平均拉脱强度为12.8 MPa,抗剪强度为9.01 MPa,钎焊接头属于脆性断裂.     

TC4钛合金消音蜂窝结构钎焊工艺

采用Ti基钎料真空钎焊方法进行了TC4钛合金消音蜂窝钎焊试验,对不同钎料添加厚度钎焊后消音蜂窝堵孔、钎焊界面焊合率、钎焊界面组织和力学性能进行了对比分析,确定了TC4钛合金消音蜂窝钎料添加厚度和钎焊工艺参数.结果表明,随着钎料添加厚度的增加,消音蜂窝带孔面板堵孔率增加,同时钎料元素对钎焊界面原始组织溶解加剧,蜂窝的拉伸力学性能下降明显.增加钎料添加厚度能够显著提高钎焊界面焊合率,当钎料添加厚度增加至30 μm以上时,能够获得焊合率良好的消音蜂窝结构.钎料添加厚度为30 μm,钎焊温度920℃,保温时间90 min时,钎焊后的钛合金消音蜂窝力学性能良好,且消音蜂窝声学性能试验测试结果和理论模型计算结果一致.     

TC4钛合金/304不锈钢异种材料蜂窝结构钎焊工艺

采用Ti-37.5Zr-15Cu-10Ni和Ag-28Cu两种钎料分别对TC4钛合金面板/304不锈钢蜂窝芯异种材料蜂窝结构进行了钎焊,对钎焊界面组织和蜂窝结构的力学性能进行了对比分析. 结果表明,Ti基钎料与304不锈钢蜂窝芯箔材界面润湿反应性能较差且Ti基钎料钎缝显微硬度较高,导致钎焊界面强度低,蜂窝拉伸力学性能差. Ag基钎料与304不锈钢蜂窝芯箔材和TC4面板均发生显著的界面反应,钎焊温度830 ℃,保温时间10 min时,蜂窝抗拉强度为10.35 MPa,呈蜂窝芯破坏特征. Ag基钎料蜂窝抗拉强度明显优于Ti基钎料结果,适用于TC4钛合金面板/304不锈钢蜂窝芯异种材料蜂窝钎焊.     

TC21钛合金动态力学性能和抗弹性能的研究

采用分离式霍普金森压杆和终点弹道实验装置,研究了α+β区和β区锻造的TC21钛合金的动态力学性能和抗弹性能。结果表明:在动态压缩试验条件下,α+β区锻造的TC21钛合金较之β区锻造的TC21钛合金具有更高的动态强度,而β区锻造的TC21钛合金的临界断裂应变更大,具有更好的动态塑性变形能力;在12.7 mm穿甲弹侵彻条件下,无论是α+β区还是β区锻造的TC21钛合金靶板的抗弹性能均与TC4钛合金靶板的抗弹性能相近,这可能是由于TC21钛合金和TC4钛合金靶板都易于发生绝热剪切破坏所导致。α+β区锻造的双态组织靶板的损伤模式为塑性扩孔导致的背部崩落破坏模式,β区锻造的片层组织靶板的损伤模式为脆性破碎模式;2种组织靶板的失效破坏均为绝热剪切带和其诱发的裂纹所导致。     

AZ31镁合金板材弯曲行为的研究

对AZ31镁合金轧制过后的中厚板进行弯曲行为研究,以探究温度对镁合金板材的弯曲的影响以及弯曲过程中镁合金板材组织变化。结果发现,弯曲断裂应力随温度升高而大幅下降,其主要原因是温度升高导致非基面滑移和孪生被激活使得板材的变形抗力下降。通过模拟弯曲过程得到镁板内侧主要受压应力,外侧主要受拉应力,实际卷取过程中断裂应变大于弯曲断裂应变。在100℃弯曲过程中镁板的拉伸区产生孪晶数量远少于压缩区,拉伸区再结晶晶粒占比为2.10%,变形晶粒占比高,大部分晶界为小角度晶界,位错密度大,（0001）极密度点在轧制接触面法向（ND）方向聚集,晶粒c轴取向向ND方向转动,导致拉伸区变形程度大、协调性差,更易发生断裂。     

一种新型锆钛合金的动态力学行为研究

通过对一种新型锆钛合金在室温下的准静态压缩和不同温度下的动态压缩实验,发现该合金在准静态和动态压缩条件下均具有良好的强度和塑性,且随着应变速率的增加和温度的降低,合金强度升高,塑性下降.基于Johnson-Cook模型,建立了该锆钛合金动态压缩下的本构关系.     

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).     

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.     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.