Al-Si-Ge-Zn钎料钎焊6061铝合金接头组织与性能分析

采用新型Al-Si-Ge-Zn钎料钎焊6061铝合金,对钎料及钎焊接头的组织和性能进行了分析,并与Al-Si-Zn和Al-Si-Ge钎料进行了对比. 结果表明,Al-Si-Ge钎料熔点较低,但高的Ge元素含量促使钎缝中形成粗大的脆性初生GeSi相,恶化了钎焊接头组织和性能;Al-Si-Zn钎料由于Zn元素含量较高,引起钎缝中Si元素偏析聚集为大片状,严重影响钎焊接头的力学性能;向Al-Si共晶中添加适量的Ge和Zn元素,维持了较低的钎料熔化温度,同时细化了钎料合金的显微组织,脆性初生GeSi相和片状硅相消失,细小分散的锗,硅固溶体相均匀分布在α-Al基体中. 采用Al-Si-Ge-Zn钎料钎焊6061铝合金,钎焊接头抗剪强度最大.     

Study on Microstructure of 6061 Aluminum Alloy Brazed with Al-Si-Zn Filler Metals Bearing Sr and Ti

制备了Sr及Ti变质的Al-Si-Zn钎料,并将其应用于6061铝合金的钎焊,研究Sr及Ti对Al-Si-Zn钎料6061铝合金钎焊性能的影响。结果表明：锌的加入使得钎料熔点由铝硅共晶温度下降至520 ℃左右。添加少量改性元素Sr及细化晶粒元素Ti,极大优化了钎料中Al-Si共晶的形态与分布,同时也细化了钎料中的α-Al固溶体。向钎料中添加0.08%Ti元素,使得原来Al-Si-Zn-Sr-0.04Ti钎料钎缝中大块团簇状的铝硅共晶均匀分布于α-Al固溶体之间。在6061铝合金钎的焊界面处可以发现较为明显的过渡层,由于钎焊过程中母材元素发生了向钎料中扩散,母材中的锰元素与钎料中的铁杂质生成块状锰铁相避免了针状β-Fe的生成     

P元素对Al-Si-Zn钎料显微组织及性能的影响

研究了P元素对Al-Si-Zn钎料的铺展性能、显微组织以及3003铝合金钎缝力学性能的影响.结果表明,在Al-Si-Zn钎料中添加P元素,能够改善钎料的铺展性能；P元素的加入不仅能有效细化钎料组织中粗大的块状初晶硅,也能使长针状的共晶硅“钝化”成短杆状.经拉伸试验发现,搭接和对接接头的断裂位置分别在母材和焊缝上；对于对接接头来说,钎焊接头的抗拉强度随Al-Si-Zn钎料中P元素含量的增加呈现先增大后减小的趋势,当P元素含量为0.06％(质量分数)时,钎料的综合性能最好.     

Al-12Si自钎剂钎料环的制备及3003铝合金的钎焊

采用热压烧结法制备了Al-12Si自钎剂钎料环,对自钎剂钎料的显微组织、润湿性以及钎焊3003铝合金接头显微组织进行了研究。结果表明,自钎剂钎料显微组织由块状初晶硅,α-Al固溶体以及颗粒状KAlF_4钎剂组成;钎料环在3003铝合金上润湿性能良好,钎焊的3003铝合金接头组织主要由α-Al固溶体和针状Si相组成,接头抗拉强度达到70 MPa。     

Sr元素对Al-Si-Zn-xSr钎料组织和性能的影响

研究了Zn,Sr元素对Al-Si-Zn钎料的铺展性能、显微组织、力学性能以及气密性的影响.结果表明,随着Zn元素含量降低,钎料的铺展面积可增大51%,6061铝合金钎焊接头的强度逐渐升高,达到120.5 MPa.当加入Sr元素后,钎料的铺展性能得到了显著提升,且随着Sr含量的增加,块状初生硅不断减少,共晶硅由针状转变为点状,并呈网状分布.当Sr元素质量分数为0.09%时,6061铝合金接头强度最高,为137.1 MPa.钎焊管路气密性测试结果表明,Al-0.2Si-77.8Zn及Al-2Si-62Zn两种钎料的气密性均逊色于Al-6.5Si-42Zn钎料.全浸试验后,Al-6.5Si-42Zn钎料的强度降低4.6%,而加入0.09%的Sr元素后钎料的强度降低3.6%.     

铝/铁复合板与铝合金超声波辅助钎焊

利用超声波辅助钎焊的方法,在大气环境、中温、无钎剂条件下,实现了铝合金与薄膜铝/铁复合板的高强、可靠连接.研究了采用Zn-Al,Al-Si钎料得到的焊缝组织及其性能.结果表明,采用Zn-Al钎料钎焊5A06铝合金和复合板,超声波能有效破除氧化膜,铝膜溶解扩散易于控制,焊缝没有金属间化合物,在铝层未完全溶解时,抗剪强度均大于70 MPa,焊缝由α-Al,η-Zn,共晶和共析组织构成;采用Al-Si钎料钎焊1100纯铝和复合板,复合板铝膜短时间内完全溶解,焊缝存在复杂的Fe-Al-Si三元化合物,并发现明显的裂纹,抗剪强度约为20 MPa.     

烧结时间对自钎剂钎料显微组织和力学性能的影响

采用热压烧结法制备了Al88Si自钎剂钎料环,研究了不同烧结时间条件下自钎剂钎料的显微组织和3003铝合金钎焊接头显微组织及力学性能.结果表明,钎料显微组织为AlSi基体、块状初晶硅相和颗粒状KAlF₄;随着烧结时间的增长,钎料中钎剂活性降低.3003铝合金钎焊接头钎缝组织由αAl固溶体和针状共晶硅相组成;随着烧结时间的增长,钎料的流铺性能越来越差,钎焊接头中裂纹、固体夹杂、未钎满、孔穴等缺陷逐渐增多,钎焊接头强度降低.     

6061铝合金中温钎焊接头组织与性能

采用自行研制的AlZnSi中温钎料,对6061铝合金进行了火焰钎焊试验,并对其接头组织及性能进行了研究.结果表明,改进的无腐蚀KCsAlF4钎剂能很好的去除铝合金表面的氧化膜,促进钎料在铝材表面铺展.Si元素在钎料中以片状或者针状相存在,在钎缝中也呈现这两种状态,并且当Si元素含量较高时,针状相明显.钎料中Si元素含量及Al元素含量较高时,钎缝中形成的针状相受力时会产生应力集中;而较高的Si元素含量及Al元素含量同时也有利于钎缝中晶粒细化.6061铝合金火焰钎焊对接接头气密性及强度均满足要求,并且两种钎料的焊接接头断口都呈现出明显的沿晶断裂特征.     

Si相形貌对4012铝合金钎料钎焊性能的影响

利用金相显微镜(OM)、扫描电子显微镜(SEM)等观测方法,研究不同Al-20Si中间合金制备的4012铝合金钎料钎焊性能.结果表明,初晶硅形貌为片状的中间合金能提高4012铝合金钎料钎焊温度,并且重熔后钎料的微观组织保留着熔化前的组织特征,证明了 Si相形貌的遗传性.     

熔体快淬铜磷合金对ZL109变质效果的影响

采用金属熔融铸造法,用熔体快淬Cu-P中间合金对ZL109活塞合金进行了变质处理,随后对变质后的合金试样进行了金相组织观察和性能检测,并对晶粒细化的机理进行了研究。结果表明:与加入传统Cu-P变质剂相比,在ZL109合金中加入熔体快淬Cu-P变质剂,使组织中的初晶硅和共晶硅得到了更好的细化,增加了界面能,减少了铸造缺陷,使其综合性能得到了进一步的提高。因此,熔体快淬处理是提高Cu-P变质剂变质效果的一种有效方法。     

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.