盐类反应制备TiB2／Al—4.5Cu复合材料的研究

采用Ｋ２ＴｉＦ６和ＫＢＦ４混合盐反应法制备ＴｉＢ２／Ａｌ－４．５Ｃｕ复合材料，通过ＳＥＭ，ＸＲＤ及ＭＴＳ等仪器研究了复合材料的凝固组织和力学性能。增强相ＴｉＢ２颗粒细小（＜２μｍ），呈近球形，均匀分布于基体之中，起强化和细化基体作用，ＴｉＢ２颗粒与基体结合好。当Ｋ２ＴｉＦ６和ＫＢＦ４混合物加入质量为基体的２０％时，复合材料的综合性能最好。ＵＴＳ达３５２ＭＰａ，ＥＬ达４．４％，ＨＢ达１４６。     

颗粒增强铝基复合材料的组织与性能

用熔铸法制备了ＴｉＢ２和ＳｉＣ颗粒增强铝基复合材料,评价了ＴｉＢ２／Ａｌ和ＳｉＣ／Ａｌ复合材料的硬度,研究了增强剂的加入方式和体积分数对ＴｉＢ２／Ａｌ复合材料拉伸性能的影响;并用扫描电镜分析了复合材料的显微组织。结果表明,ＴｉＢ２颗粒对Ａｌ基体的增强效果比ＳｉＣ颗粒好,Ｔｉ,Ｂ化合物的增强效果优于ＴｉＢ２粉末,复合材料的力学性能随ＴｉＢ２体积分数增加而提高;用含Ｔｉ,Ｂ化合物的混合物增强的１．５％ＴｉＢ２／Ａｌ（体积分数）复合材料的热轧退火态性能为σｂ１６０．４ＭＰａ,δ１３．１％,铸态ＨＢ４５１ＭＰａ。ＳＥＭ观察结果表明,在铝基体中添加Ｔｉ、Ｂ化合物的混合物能在基体中原位生成ＴｉＢ２颗粒。     

工艺参数对铝晶粒细化剂中间合金中铝化合物形态的影响

本文就工艺参数对Ａ１－Ｔｉ和Ａｌ－Ｚｒ合金（制备时用铝还原Ｋ２ＴｉＦ６和Ｋ２ＺｒＦ６）显微组织的影响进行了研究。当还原发生在液＋固两相区时生成块状铝化物（分别为ＴｉＡｌ３和ＺｒＡｌ６）。当还原发生在液相单相区时则生在片状铝化物。对合金组织而言，使用Ｎａ２ＴｉＦ６比使用Ｋ２ＴｉＦ６有更好的影响。随后的冷却速度进一步影响合金的微组织和块或片状铝化物的尺寸。Ａｌ－５Ｔｉ－０．２Ｂ（重量百分比）合金...     

自生复合材料（Al－TiB_2－TiC）的燃烧合成研究

本文研究了Ａｌ－Ｔｉ－Ｂ４Ｃ体系的燃烧合成过程，用粉末（Ａｌ、Ｔｉ、Ｂ４Ｃ）通过燃烧方法，来制备复合材料（Ａｌ－ＴｉＢ２－ＴｉＣ）．采用ＤＴＡ、ＸＲＤ和ＳＥＭ技术对复合材料的形成和结果进行了分析研究，得到如下结果：分别用８０％Ａｌ＋２０％（３Ｔｉ＋Ｂ４Ｃ），９０％Ａｌ＋１０％＋１０％（３Ｔｉ＋Ｂ４Ｃ）原料粉末，通过快速加热可得到Ａｌ－ＴｉＢ２－ＴｉＣ，在制备过程中会产生少量的ＴｉＡｌ３．     

自生复合材料（Al—TiB2—TiC）的燃烧合成研究

本文研究了Ａｌ－Ｔｉ－Ｂ４Ｃ体系的燃烧合成过程，用粉末（Ａｌ，Ｔｉ，Ｂ４Ｃ）通过燃烧方法，来制备复合材料（Ａｌ－ＴｉＢ２－ＴｉＣ）。采用ＤＴＡ、ＸＲＤ和ＳＥＭ译复合材料的形成和结果进行了分析研究，得到如下结果：分别用８０％Ａｌ＋２０％（３Ｔｉ＋Ｂ４Ｃ），９０％Ａｌ＋１０％（３Ｔｉ＋Ｂ４Ｃ）原料粉末，通过忆热可得到Ａｌ－ＴｉＢ２－ＴｉＣ，在制备过程中会产生少量的ＴｉＡｌ３．     

Ti形态对原位生长陶瓷粒子增强Al复合材料微观结构的影响

采用Ｔｉ－Ａｌ－Ｂ和ＴｉＯ２－Ａｌ－Ｂ两个体系利用反应热压方法制备了原位ＴｉＢ两粒子增强Ａｌ（ＴｉＢ２／Ａｌ）和原位Ａｌ２ＯＥ，ＴｉＢ２粒子复合增强Ａｌ（Ａｌ２Ｏ３．ＴｉＢ２）／Ａｌ两种复合材料。研究表明，对于Ｔｉ－Ａｌ－Ｂ体系，除ＴｉＢ２外还有一定量的尺寸可达几十微米的Ａｌ３Ｔｉ生成，原位形成的ＴｉＢ２大部分为０．１－０．５μｍ的块状粒子，此外还有少量长宽比在于４的棒状ＴｉＢ２对于ＴｉＯ－ＡｌＯ     

反应物形态对原位生长陶瓷粒子增强铝基复合材料微观结构和拉伸性能的影响

对Ｔｉ－Ａｌ－Ｂ,ＴｉＯ２－Ａｌ－Ｂ和ＴｉＯ２－Ａｌ－Ｂ２Ｏ３三个体系利用反应热压方法制备了原位ＴｉＢ２粒子增强Ａｌ（ＴｉＢ２／Ａｌ）和原位Ａｌ２Ｏ３,ＴｉＢ２粒子增强Ａｌ（Ａｌ２Ｏ３·ＴｉＢ２／Ａｌ）复合材料．Ｔｉ－Ａｌ－Ｂ体系中形成的ＴｉＢ２为最大尺寸可达５μｍ的具有一定长宽比的块状或棒状粒子,此外还有一定量尺寸可达几十微米的不规则块状Ａｌ３Ｔｉ生成．ＴｉＯ２－Ａｌ－Ｂ体系中形成小于２μｍ等轴的Ａｌ２Ｏ３和ＴｉＢ２粒子,基本没有Ａｌ３Ｔｉ生成．ＴｉＯ２－Ａｌ－Ｂ２Ｏ３体系中除细小等轴状的Ａｌ２Ｏ３和ＴｉＢ２粒子外,还生成尺寸为几十微米的条状Ａｌ３Ｔｉ．拉伸试验表明,由ＴｉＯ２－Ａｌ－Ｂ体系制备的复合材料具有最高的强度和塑性．对三个体系所制备复合材料差异的微观结构和性能做出了解释．     

Ti形态对原位生长陶瓷粒子增强Al复合材料微观结构的影响

采用Ｔｉ－Ａｌ－Ｂ和ＴｉＯ２－Ａｌ－Ｂ两个体系利用反应热压方法制备了原位ＴｉＢ２粒子增强Ａｌ（ＴｉＢ２／Ａｌ）和原位Ａｌ２Ｏ３，ＴｉＢ２粒子复合增强Ａｌ（Ａｌ２Ｏ３．ＴｉＢ２／Ａｌ）两种复合材料，研究表明，对于Ｔｉ－Ａｌ－Ｂ体系，除ＴｉＢ２外还有一定量的尺寸可达几十微米的Ａｌ３Ｔｉ生成，原位形成的ＴｉＢ２大部分为０．１－５０μｍ的块状粒子，此外还有少量长宽比大于４的棒状ＴｉＢ２．对于ＴｉＯ２－Ａｌ－Ｂ体系，基本上没有Ａｌ３Ｔｉ生成，原位形成的Ａｌ２Ｏ３和ＴｉＢ２为００５－２０μｍ的近似等轴状的粒子．对两种复合材料差异的微观结构给出了解释．     

内生TiB2颗粒增强TiB2/Al-7%Si-0.5%Mg复合材料的组织和力学性能

了氟盐反应法（ＬＳＭ）制备ＴｉＢ２颗粒增强Ａｌ－７％Ｓｉ－０．５Ｍｇ复合材料的物相组成和力学性能。结果表明,当含５％ＴｉＢ２时,复全材料中可以生成稳定且均匀分布的ＴｉＢ２颗粒,未发现ＴｉＡｌ３等相。除δ５外,复合材料的各项力学性能均有不同程序提高,弹性模量有较大幅度提高。     

用热化学处理改善（α＋β）型钛合金的组织和力学性能

研究了以氢为临时合金元素的热化学处理（ＴＣＰ）对（α＋β）型钛合金的组织、拉伸性能和断裂韧性的影响。结果表明，几种ＴＣＰ工艺对Ｔｉ－６Ａｌ－４Ｖ合金的魏氏组织和Ｔｉ－５Ａｌ－２．５Ｆｅ合金的锻造组织均有显著的细化作用，明显提高合金的屈服强度。作者提出的新工艺可提高Ｔｉ－５Ａｌ－２．５Ｆｅ合金的延伸率。ＴＣＰ降低Ｔｉ－６Ａｌ－４Ｖ合金的断裂韧性（Ｊ＿１ｃ），但明显改善Ｔｉ－５Ａｌ－２．５Ｆｅ合金的断裂韧性。     

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.