电解加钛铝合金的晶粒细化及其制备铝-硅合金的组织和性能

研究了电解加钛的晶粒细化作用,与AlTi和AlTiB细化剂对纯铝的晶粒细化效果进行了比较;对用电解低钛铝合金制备的A356合金和由纯铝制备并用AlTi或AlTiB细化处理的A356合金的组织与性能进行了对比研究;进行了利用工业铝电解槽生产的电解低钛铝合金熔体直接生产A356合金的工业试验。结果表明：电解加钛具有显著的晶粒细化作用,其细化能力与AlTiB的相当,明显优于AlTi中间合金的。在试验室条件下,用电解低钛铝合金制备的A356合金与纯铝制备并用中间合金细化处理的A356合金的拉伸性能相当;将电解低钛铝合金熔体直接用于铝．硅合金的生产是可行的,并具有节约能源,细化处理工艺简单,产品质量良好的特点。     

硼对电解低钛铝基合金微观组织的影响

研究了Al-B中间合金对工业纯铝和电解低钛铝基合金微观组织的影响.结果表明,硼对纯铝晶粒细化作用较弱;对于电解低钛铝基合金而言,由于在电解过程加入的微量钛的作用,其晶粒已经得到明显细化,且随着钛含量的增加,晶粒细化效果不断加强.向电解低钛铝基合金按Ti:B=5:1的重量比再熔配加入Al-B中间合金,可明显改善电解加钛的晶粒细化作用,特别是在钛含量较低时作用更加明显,随着Al-B中间合金添加量的增加,硼的作用逐渐减弱,最终与不加硼的电解低钛铝基合金的细化效果相当.     

Ti与含Ti或B中间合金对铝晶粒细化效果及抗高温衰退能力的影响

对比研究了电解加钛和含钛或硼中间合金对铝的晶粒细化效果及抗高温衰退能力的影响.结果表明,电解加钛和Al-5Ti中间合金在熔体温度较低时具有较好的晶粒细化效果,但随着熔体温度的升高,细化效果均迅速衰退;电解加钛再熔配加Al-4B中间合金可在熔体温度为720℃时获得最佳的细化效果,随着熔体温度的升高细化效果有所衰退,但衰退速度较慢;在加入Al-5Ti的同时加入Al-4B中间合金可明显提高Al-5Ti的晶粒细化效果和抗高温衰退能力,但效果不如电解加钛加Al-4B中间合金;Al-5Ti-1B中间合金具有最强的抗高温衰退能力,随着熔体温度的升高,晶粒不但不粗化反而有所下降,当熔体温度高于900℃时,才出现衰退现象.对试验结果及晶粒细化机制进行了分析.     

不同加钛方法对6063合金细化的研究

加钛方式不同，钛含量不同，对铝及其合金的晶粒细化效果不同。对比研究了用电解低钛铝合金、加Al—5Ti中间合金、Al—5Ti—1B中间合金及电解低钛铝合金加Al—B中间合金4种加钛方式及不同钛含量对6063合金的晶粒细化效果。研究结果表明：不同的加钛方式对6063合金均有明显的细化效果，随着钛含量增加，晶粒逐渐变细；钛含量相同时，电解加钛的细化效果优于Al—5Ti中间合金的细化效果；当合金中含有硼时，钛含量相同时，电解加钛加Al—B中间合金的细化效果优于加Al—5Ti—1B的细化效果。     

B对电解低钛铝制备的6009铝合金微观组织的影响

研究了Al-B中间合金对工业纯铝和电解低钛铝制备的6009铝合金微观组织的影响.结果表明,Al-B中间合金对纯铝制备的6009合金的晶粒细化作用很弱,而对电解低钛铝制备的6009合金有明显的细化作用.对电解低钛铝制备的6009合金而言,当Ti含量为0.05%时,晶粒细化效果在w(B)/w(Ti)＝1∶5时最好;而在w(B)/w(Ti)＝1∶2.22时晶粒明显粗化,之后合金的晶粒尺寸又随着B含量的增加而有所下降.     

钛、硼对铝及铝合金晶粒细化的研究与发展

一、钛、硼对铝合金晶粒细化的研究状况 在工业铝合金中加入微量的钛或钛和硼,会使其最终凝固组织显著细化。文献指出,使铸锭和铸件的凝固组织细化,具有明显提高合金的力学性能,不易产生裂纹和冷隔,减少偏析,改善压延性能等优点。 1.晶粒细化剂的添加方法 铝合金中添加晶粒细化剂有两种方法: ①中间合金加入法 通常采用的中间合金有Al-Ti、Al-B、Al-Ti-B、Al-Ta等,但Al-Ti和Al-Ti-B中间合金使用最广泛。在Al-Ti中间合金中含3～5%Ti,而Al-Ti-B中间合金通常含5%Ti和0.5～2.5%B。配制中间合金增加了操作工序和中间合金自身的偏析,是这种方法的     

加钛和加硼方式对铝合金的晶粒细化及其衰退行为的影响

通过对比实验,研究了电解加钛与经Al-Ti、Al-Ti-B中间合金向工业纯铝熔配加钛的晶粒细化效果及其衰退行为,以及Al-B中间合金对电解低钛铝合金的晶粒细化效果及衰退行为的影响,还分析了硼对电解低钛铝合金的晶粒细化和抗衰退行为的影响.结果表明,在钛含量为0.10%和0.15%的条件下,电解加钛晶粒细化作用的衰退速度比熔配加Al-Ti中间合金要慢;熔配加Al-Ti-B中间合金细化晶粒作用的抗衰退能力则明显高于电解加钛和熔配加Al-Ti中间合金;加Al-B中间合金可有效提高电解低钛铝合金的细化效果和抗衰退能力,并使其明显高于电解加钛和熔配加Al-Ti或Al-Ti-B中间合金.     

用氟化物和金属粉制取铝-钛-硼中间合金

用 Al-Ti 中间合金处理铝熔体的传统方法已有30余年的历史。此法至今仍为某些冶金工作者在某些场合所使用。进一步研究查明,钛与硼结合使用,在加钛浓度低得多的情况下可以大大促进成核过程。例如,最近证明,采用 Al5TilB 中间合金对99.7%纯铝加入0.005%Ti,能使铸锭晶粒达到200微米以下,而用 Al5Ti 中间合金达到同等的细化晶粒效果则需要加入0.06%Ti,     

电解低钛铝合金在变形合金6063中的应用研究

研究了电解低钛铝合金的细化效果，结果表明，通过电解加低含量的钛可以使工业纯铝晶粒明显细化，由粗大的柱状晶变成等轴晶。用电解低钛铝合金直接配制6063合金时，得到的也是细小均匀的等轴晶粒。钛含量相同时，电解低钛铝合金的细化效果优于铝-钛中间合金的细化效果。     

电解加钛与熔配加钛对工业纯铝晶粒细化的作用

对比研究了电解加钛,以Al-Ti和Al-Ti-B中间合金方式向工业纯铝熔配加钛以及向电解低钛铝合金中再熔配加Al-B中间合金的细化效果.结果表明,不同加钛方式对纯铝都有较强的细化作用; 在钛含量相同的条件下,电解加钛的晶粒细化能力明显高于熔配加Al-Ti中间合金的; 钛含量较低时,熔配加Al-Ti-B中间合金的细化效果略好于电解加钛的,钛含量较高时,二者的细化能力相当.向电解生产的低钛铝合金中再熔配加入Al-B中间合金,可明显改善晶粒细化效果,尤其在较低的钛含量时表现得非常明显.     

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.