熔体复合净化处理对砂型铸造Mg-10Gd-3Y-0.5Zr镁合金显微组织和力学性能的影响（英文）

采用金相分析、SEM和拉伸试验等试验方法分析和测试砂型铸造Mg-10Gd-3Y-0.5Zr镁合金熔体复合净化处理(旋转喷吹氩气结合熔剂净化)后的显微组织和室温力学性能,讨论复合处理方法净化机理。结果表明,该复合处理可以显著提高熔体质量,大幅度提高合金力学性能。熔体经过复合净化处理后,合金夹杂物体积分数从0.47%降低到0.28%,抗拉强度和伸长率从245 MPa和0.7%分别提高至312 MPa和4.5%。1%熔剂复合旋转喷吹气体净化效果甚至更优于传统的2%熔剂净化效果,熔剂的使用量减少了50%,显著提高了净化效率,并缓和了熔剂净化带来的环境污染问题。     

复合精炼对Al-Si合金净化效果的试验研究

研究了复合精炼对铝硅合金熔体的净化效果，并介绍了铝硅合金熔体中主要氧化夹杂物与气体的存在形态及其相互作用。试验结果表明：在铝熔体较少的情况下，复合精炼法是精炼铝硅合金，降低含气量最有效的办法．其净化效果优于试验中常用的吹气法和熔剂法。     

JDN-I熔剂对Al-Si合金的影响

采用根据铝熔体覆盖保护和原子净化原理研制的JDN I熔剂 ,对ZL10 1A和ZL114A两种重要的Al Si合金进行净化处理试验发现 ,JDN I熔剂能够大大提高上述两种合金的综合性能 ,从而可以很好地满足这两种合金铸件的性能要求 ;而熔剂A对上述两种合金的作用效果不明显 ,常常不能满足合金的使用要求。试验结果还表明 ,采用JDN I熔剂净化处理ZL10 1A合金熔体 ,熔损仅为 0 75 % ,是C2 Cl6的 12 % ,为熔剂B的 65 2 %。     

稀土熔剂对A00熔体作用时间的研究

在730℃温度下,用JDN-I稀土熔剂对A00纯铝进行净化处理,结果表明,净化后的铝熔体氢含量随着保温时间的延长增加很小,纯铝的力学性能在保温100min后急剧降低,纯铝熔体的熔损在保温100min后,随着保温时间的增加也急剧升高,但远低于市售熔剂A,熔体熔损基本都保持在1%以下;该种熔剂对纯铝熔体最适宜的处理时间是小于100min.     

镁熔体净化技术的研究进展

镁作为新兴轻质材料在汽车、3C和航空航天领域的应用逐渐普及,伴随行业节能减排的要求提升以及材料行业的迭代更新,镁及其合金所涉及的产业领域将会进一步扩大。而镁及其合金在铸造与变形加工前,镁熔体纯净度会对其性能产生巨大影响,如熔体纯净度低会显著降低合金的抗拉强度、伸长率等力学性能,导致合金出现炸裂、破损现象。为此,镁熔体的高效除气除杂净化技术成为研究热点。镁熔体净化作为镁熔炼过程中的重要环节,一直是科研工作者不断改进优化的研究课题。本文在简要介绍镁熔体中夹杂物来源的基础上,归纳了适用于镁熔体的熔剂净化、无熔剂净化、复合净化法及其净化效果,且对真空蒸馏法净化镁熔体的相关研究进行了探讨,系统综述了镁熔体净化技术研究进展,展望了该技术的未来研究方向。     

铝熔体熔剂的应用与研究

分析铝熔体熔剂分类和作用特点,指出现有熔剂应用和研究的不足,提出铝熔体熔剂的发展方向.还介绍了铝熔体覆盖保护和化学净化的原理以及基于该理论研制的新型净化熔剂和净化效果.     

电工铝杆用高效排杂净化熔剂及其处理效果

探讨了电工铝杆用高效排杂净化熔剂及其处理效果。结果表明:熔剂组成对其净化效果具有重要影响;DJ-1熔剂是电工铝杆的一种高效排杂净化熔剂,当其与特定的过滤工艺配合时,净化效果显著,除杂率及气孔降低率分别可达83.6％和91.2％,并有效改善了杂、气存在形态,从而直接影响到材料的微观断裂过程,显著提高了铝材的力学性能,尤其是塑性。采用该熔剂净化后进行晶粒细化处理,可充分发挥细化处理效果,明显提高了电工铝杆性能,尤其在σb>120 MPa时,伸长率仍达12.2％(与常规处理相比,提高幅度达62.7％),电阻率也降低了0.93％。     

电热法生产过共晶Al-Si合金的组织与性能研究

对电热法生产铝硅合金配制的Al-20Si合金进行了P-RE复合变质处理,对变质后的微观组织和力学性能进行了分析.结果表明,合金经复合变质后,合金的初晶硅尺寸得到明显细化,共晶硅由长针状变为短杆状或者细小的颗粒状;其抗拉强度由182MPa提高到205MPa,提高12.6%了,其伸长率由0.22%提高到0.26%,提高了18.2%.然而与纯铝配制的过共晶铝硅合金相比,其抗拉强度和伸长率都相对较低,原因在于电热法生产铝硅合金配制的过共晶铝硅合金中Fe含量较高.     

精炼工艺对铸造Al-2Li-2Cu-0.2Zr合金夹杂物和力学性能的影响（英文）

研究不同精炼工艺对铸造Al-2Li-2Cu-0.2Zr合金夹杂物和力学性能的影响,包括双级C_2Cl_6精炼工艺,双级氩气旋转喷吹精炼工艺和双级复合精炼工艺。结果表明,结合C_2Cl_6和氩气旋转喷吹的双级复合精炼工艺可以显著提高铸造Al-2Li-2Cu-0.2Zr合金的熔体纯净度和力学性能。与未精炼的合金相比,通过双级复合精炼工艺得到的合金气孔缺陷和夹杂物的体积分数从1.47%下降到0.12%,固溶处理后合金的屈服强度、抗拉强度和伸长率分别从113 MPa、179 MPa和3.9%提高至142 MPa、293 MPa和18.1%。合金熔炼过程中,在加入锂之前首先使用C_2Cl_6精炼进行除气以及除掉熔体中较大尺寸的夹杂物,在加入锂之后使用氩气旋转喷吹进一步除气以及除掉熔体中细小的悬浮夹杂物。双级复合精炼工艺不仅可以有效去除熔体中的气体和夹杂物,还可以大幅度降低锂元素的氧化烧损,结合两种精炼方法的各自优势,取得显著的精炼效果。     

搅拌时间对P变质的Al-20%Si合金初生硅尺寸与力学性能的影响

对Cu-9%P中间合金变质的Al-20%Si合金熔体进行了搅拌处理,研究了搅拌时间对P变质的Al-20%Si合金初生硅尺寸与力学性能的影响。研究表明:机械搅拌使Cu-P合金周围形成的Al P细小,同时使其弥散地分布于Al-Si合金熔体中,作为初生硅的结晶核心。随着搅拌时间的增加,初生硅由棱角尖锐、粗大的块状变为尖角钝化的颗粒状,搅拌时间从8 min增加到28 min时,初生硅尺寸由56.56μm减小到21.74μm,试样的抗拉强度由96.2 MPa增加到164.3 MPa,提高了70.8%,伸长率由1.5%提高到2.5%,提高了66.7%。     

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.