细晶铝锭熔炼的6063铝合金组织与性能研究

细晶铝锭是采用纯铝的电解设备,通过向铝电解槽中添加TiO2,直接电解生产的晶粒细化的铝锭.采用细晶铝锭熔炼6063铝合金,并对其组织性能进行研究,结果表明:细晶铝锭熔炼6063铝合金,由于其电解加钛方式,生产成本低廉;细晶铝锭熔炼的6063铝合金型材,晶粒细小均匀,表面性能及力学性能完全满足GB/T 5237的要求;细晶铝锭、RE(富铈混合稀土)元素联合细化,细晶铝锭、RE、B元素联合细化熔炼的6063铝合金,抗拉强度与添加Al-5Ti-1B熔炼的6063铝合金相当,而伸长率提高20%,并可获得更优异的表面性能.     

细晶铝锭熔炼的6063铝合金铸态组织与性能研究

细晶铝锭是采用纯铝的电解设备,通过向铝电解槽中添加TiO2,直接电解生产的晶粒细化的铝锭。采用细晶铝锭熔的6063铝合金与AlTi5B1、AlTi5中间合金细化的6063铝合金铸态组织性能进行对比研究。结果表明:AlTi5B1中间合金细化效果最好,AlTi5中间合金细化效果最差,细晶铝锭的细化效果居中;6063铝合金铸态组织硬度,在钛含量低于0.05%时,主要由Mg2Si含量决定,晶粒大小对硬度的影响较小。     

电解掺钛对纯铝晶粒细化作用效果的分析

向铝电解槽添加一定量的二氧化钛可使生产的铝锭中含有少量的钛。分析了用这种掺钛方式生产的低钛铝合金的微观组织，对比研究了电解掺钛与通过铝钛中间合金掺钛的晶粒化效果。结果表明。电解掺钛具有更优良的晶粒细化作用。随着电解掺钛量的增加，晶粒尺寸下降。电解掺钛量在0．20％～0．30％之问既可得到满意的细化效果。还分析了电解掺钛的晶粒细化作用的机理，对电解掺钛新工艺的可用性进行了评价。     

细化及变质方法对A356铝合金微观组织的影响

在对比研究细晶铝锭和铝钛中间合金2种不同加钛细化方法的基础上,研究锶、稀土、锶 稀土不同变质方法处理后A356铝合金的铸态微观组织变化。结果表明:细晶铝锭细化效果较铝钛中间合金好,经细晶铝锭 锶 稀土联合处理的A356铝合金,晶粒细小,变质充分,针孔较少,组织均匀,是一种优良的细化变质方法。     

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。     

细晶铝锭熔炼的A356铝合金组织与性能的研究

研究了不同细化和变质方法对细晶铝锭熔炼的A356铝合金组织与性能的影响。结果表明,钛(由细晶铝锭加入)、硼及稀土联合细化,晶粒细化效果最好;0.04%的锶、0.01%的钛、0.03%的硼及0.3%的稀土联合细化及变质的A356铝合金晶粒细小,硅颗粒细碎,气孔较少,具有较高的力学性能。     

不同加钛方式对Zn-Al合金组织及耐磨性的影响

采用了工业上常用的3种加钛方式(电解低钛铝基合金、氟盐、铝钛中间合金)细化高铝锌合金,对比了不同加钛方式对合金组织及耐磨性的影响。研究结果表明,Ti作为一种晶粒细化剂能够有效地细化合金的晶粒,其中电解加钛的细化效果最明显。其原因可归因于强大电磁场的搅拌作用下Ti原子的均匀分布以及原位析出的异质形核质点的形核作用。由于晶粒的细化,增加了晶界面积,更有效地抑制了位错的产生,从而增强了基体的结合力,因而电解加钛合金的耐磨性最高。     

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。     

RE对细晶铝锭细化效果的影响

利用光学显微镜、扫描电镜、能谱分析等方法研究分析了不同RE添加量对细晶铝锭细化效果的影响。试验结果表明，混合RE对细晶铝锭有明显的晶粒细化作用。随着RE含量的增加，晶粒平均直径减小。当RE的质量分数达到0．30％时，可得到最好的晶粒细化效果；当RE的质量分数超过0．30％后，细化效果开始下降。并分析了添加RE后细晶铝锭细化晶粒作用的机理。     

电解低钛汽车轮毂材料的研究

本文应用原位钛合金化、细晶化的电解低钛铝基合金为母材生产汽车轮毂材料——A356合金，对其微观组织及性能进行了研究。研究发现：电解低钛A356合金较传统的熔配加钛A356合金组织细化，一次枝晶细小，二次枝晶臂间距短；经过T5短时处理，硅相球化良好，颗粒细小，强化元素Si、Mg在基体中均匀、弥散析出。电解低钛A356合金具有高强度和高韧性的良好力学性能匹配，σь≥300MPa和δ≥8％的性能比传统熔配加钛的A356合金强度和塑性均可提高20％以上。     

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.