Ti（C，N）基金属陶瓷与45钢的真空钎焊

以AgCuZn合金为钎料,采用真空钎焊方法实现了Ti(C,N)基金属陶瓷与45钢的牢固连接.研究了连接温度、保温时间和钎料厚度对钎缝接头抗剪强度的影响,并对连接界面区域的微观结构及焊料反应产物进行了SEM, EDS及XRD分析.在本试验中,当连接温度为850 ℃、保温时间为15 min、钎料厚度为 0.4 mm时,得到的接头界面抗剪强度最高,为145.2 Mpa.微观结构结果表明:钎料与两侧母材润湿良好,分别在两侧形成了界面扩散互溶过渡层,良好的界面扩散互溶过渡层是获得较高界面连接强度的主要原因.     

SiCp/Cu复合材料的真空钎焊

对冷压烧结结合热挤压工艺制备的SiC/Cu复合材料,选用Ti和AgCuTi为钎料,采用不同的工艺进行真空钎焊试验.用金相显微镜和扫描电镜对母材和钎焊接头的剪切断口形貌进行分析,利用电子万能试验机对钎焊接头进行抗剪强度测试,将接头抗剪强度与母材抗剪强度进行对比以评判钎缝质量.结果表明,用Ti为钎料连接SiCp/Cu复合材料的连接状况要优于AgCuTi钎料,且连接温度850℃,保温时间为20 min时,抗剪强度最大为70.5 MPa,与母材抗剪强度相当;随着铜基复合材料中SiCp含量不断增加,钎焊接头室温抗剪强度不断下降,当SiCp含量超过10%时,抗剪强度快速下降.     

TiC金属陶瓷/钢钎焊接头的界面结构和连接强度

采用BAg45CuZn钎料对自蔓延高温合成的TiC金属陶瓷与中碳钢进行了真空钎焊连接,利用扫描电镜、电子探针、X射线衍射等分析手段对接头的界面结构和室温抗剪强度进行了研究.结果表明,利用BAg45CuZn钎料可实现TiC金属陶瓷与中碳钢的连接;接头的界面结构为TiC金属陶瓷/(Cu,Ni)固溶体/Ag基固溶体 Cu基固溶体/(Cu,Ni)固溶体/(Cu,Ni) (Fe,Ni)/中碳钢;在连接温度为850℃保温10min的钎焊条件下,接头的抗剪强度可达121MPa.     

Ti-Zr-Cu-Ni-Fe-Co-Mo钎料合金钎焊γ-TiAl/GH536接头的显微组织与剪切强度（英文）

采用Ti-Zr-Cu-Ni-Fe-Co-Mo作为钎料,在钎焊温度1090～1170℃、钎焊时间0～20 min的工艺参数下,实现γ-TiAl和GH536合金的钎焊连接,利用SEM、EDS、XRD和万能试验机研究钎焊温度和钎焊时间对钎焊接头显微组织和剪切强度的影响。结果表明:不同工艺参数下获得的γ-TiAl/GH536钎焊接头均包括4个界面反应层。随着钎焊温度的升高和钎焊时间的延长,钎缝宽度和钎焊接头的平均抗剪强度均是先增大后减小。钎焊温度1150℃、钎焊时间10 min时获得的钎焊接头的剪切强度最大,达262 MPa。Al₃NiTi₂和TiNi₃脆性金属间化合物是产生裂纹和降低接头强度的主控因素,Al₃NiTi₂脆性金属间化合物几乎占据整个呈典型解理断裂特征的剪切断口表面。     

奥氏体不锈钢与纯铜的真空钎焊工艺研究

采用BAg72Cu共晶钎料对奥氏体不锈钢与纯铜的真空钎焊工艺进行研究.通过剪切试验、光学显微镜观察、扫描电镜及能谱分析等手段研究了钎焊温度和保温时间对钎焊接头组织和性能的影响.试验表明,钎缝中心区为AgCu共晶组织,两侧界面反应区为铜基固溶体,钎焊温度对钎焊接头的组织和性能影响明显,而保温时间对其影响不明显.当钎焊温度865℃、保温时间10min时,剪切强度最高,达到160 MPa.钎焊温度过低时,冶金作用较弱,接头强度较低;钎焊温度过高时,钎料流淌较多,接头强度也较低.以865℃为钎焊温度,改变保温时间,在10～45 min保温时间内接头的剪切强度变化不大.     

钎焊工艺参数对TC4钛合金钎焊接头组织及性能的影响

在钎焊温度为780～900℃,钎焊时间为2～30 min的条件下,采用Ag-28Cu钎料对TC4钛合金进行了真空钎焊试验。利用金相显微镜、扫描电镜及能谱仪对接头微观组织进行了研究。结果表明,接头形成3个反应区:扩散区Ti_2Cu+Ti(s.s)、界面反应区Ti_2Cu/TiCu化合物以及钎缝中心区的Ag(s.s)+Cu(s.s)。随着钎焊温度的提高和保温时间的延长,扩散区及界面层的厚度增加,但过高的工艺参数会导致钎料流失从而使钎缝宽度降低。在钎焊温度为820℃,保温时间为10 min时,钎焊接头的抗剪强度最高,为121 MPa。     

采用Ni-Cr-P-Cu钎料钎焊不锈钢接头组织及抗剪强度研究

采用Ni-Cr-P-Cu钎料对316L不锈钢进行真空钎焊连接,分析了不同钎焊温度(930~980℃)和保温时间(5~30 min)对接头组织及抗剪强度的影响。结果表明,不锈钢与钎料的界面组织为镍基固溶体(固溶原子为Cu,Fe和Cr),而钎缝中心的组织为镍基固溶体-Cr Ni P共晶相以及Ni3P-镍基固溶体共晶相,其中共晶相中的镍基固溶体属于韧性相,弥散分布于钎缝中。升高钎焊温度或延长保温时间都会增加不锈钢和钎料界面的镍基固溶体的厚度,同时会增加钎缝中心韧性相的数量。当钎焊温度为980℃,保温时间30min时,接头的抗剪强度最大,为95 MPa。     

Ti(C,N)基金属陶瓷与低碳钢真空钎焊的界面结构及接头强度

本文采用CuMnNiCrSi钎料实现了对Ti(C,N)基金属陶瓷与低碳钢的真空钎焊连接。研究了钎焊温度和保温时间对钎焊接头剪切强度的影响,通过XRD、SEM和EDS对接头的物相、显微组织、元素分布及断口形貌进行分析。研究表明:在钎焊温度为1030℃,保温时间为20 min的工艺条件下,钎焊接头的结合强度达到最大,其剪切强度为301.5 MPa。Ti(C,N)基金属陶瓷/低碳钢焊缝由α-Ti基固溶体和Cr基固溶体构成。在金属陶瓷一侧的界面处形成Cu基固溶体,在钢一侧形成(Cu,Ni)固溶体和(Fe,Ni)固溶体。Ti(C,N)基金属陶瓷/低碳钢接头断裂发生在Cu基钎料处,其断裂方式为韧性断裂。     

AgCuNiLi钎焊TiC金属陶瓷与GH3128界面结构及接头性能

采用AgCuNiLi钎料对TiC金属陶瓷与GH3128镍基高温合金进行钎焊。结果表明:当钎焊温度为840℃,保温10min时,接头典型界面结构可以表示为:TiC金属陶瓷/(Cu,Ni)/Ag(s.s)+Cu(s.s)/(Cu,Ni)/GH3128。随着钎焊温度的升高或保温时间的延长,TiC金属陶瓷附近的(Cu,Ni)固溶体层厚度增大,且向钎料内部呈树枝状长大,钎料内部的Ag-Cu共晶组织逐渐减少。界面机理分析表明:钎料中Li的加入能促进界面上(Cu,Ni)固溶体的形成;但(Cu,Ni)固溶体的继续长大则受钎料中Cu元素的扩散程度控制。当加热温度由810℃升高到960℃,接头抗剪强度呈现先增大,然后缓慢减小的变化趋势。当加热温度为880℃、保温时间为10min时,接头抗剪强度达到最大值204MPa。     

YSZ陶瓷与Kovar合金的银基钎焊研究

用BAg72Cu钎料对氧化钇稳定氧化锆(YSZ)陶瓷与Kovar合金进行真空钎焊封接,用SEM、EDS和氦质谱检漏仪考察了钎焊温度和钎焊厚度对钎焊封接件的抗剪强度和气密性的影响,并分析了钎焊界面微观结合情况。结果表明,YSZ陶瓷与Kovar合金在850℃保温5 min钎焊封接时,获得的封接件能够承受最大的抗剪强度为75 MPa;钎缝氦漏率优于6.0×10^-11 Pa.m³/s,钎缝无气孔、裂纹现象,钎缝中间区域主要为银基钎料凝固组织,Kovar合金侧界面反应区富集铜合金,铂金属化层侧为富银相。     

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.     

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.