快速凝固Al—TiC自生复合材料的显微组织和力学性能

将常规熔铸工艺与快速凝固技术相结合，成功地制备出Ａｌ－ＴｉＣ自生复合材料．常规熔铸Ａｌ－ＴｉＣ自生复合材料中ＴｉＣ的体积分数为１４．５％，颗粒尺寸为０．２－１．０μｍ，一般呈聚集态分布；与类似工艺条件下的人工复合材料相比，业已表现出较好的综合力学性能．快凝及热挤成型以后，ＴｉＣ的体积分数约为１３．５％，颗粒尺寸减至４０－８０ｎｍ，并弥散分布于晶粒尺寸为０．３０－０．８０μｍ的α－Ａｌ基体上，室温拉伸强度增加了约１００ＭＰａ，表现出良好的高温力学性能．     

原位TiC粒子增强Al－Si合金的组织及性能SCIEI

采用新工艺方法──熔铸直接接触反应法制取原位ＴｉＣ粒子增强铸造Ａｌ基复合材料．该方法是将Ａｌ－５．６ｗｔ－％Ｓｉ合金升温至７５０℃，再把Ａｌ－４０ｗｔ－％Ｔｉ－１０ｗｔ－％Ｃ粉末压制块压入，使Ｔｉ和Ｃ在Ａｌ－Ｓｉ合金液中直接反应生成直径为０．１－１．０μｍＴｉＣ颗粒，并均匀地分布在α－Ａｌ基体中，晶界上无明显颗粒聚集，制成品性能优异．     

原位TiC粒子增强Al－Si合金的组织及性能

采用新工艺方法──熔铸直接接触反应法制取原位ＴｉＣ粒子增强铸造Ａｌ基复合材料．该方法是将Ａｌ－５．６ｗｔ－％Ｓｉ合金升温至７５０℃，再把Ａｌ－４０ｗｔ－％Ｔｉ－１０ｗｔ－％Ｃ粉末压制块压入，使Ｔｉ和Ｃ在Ａｌ－Ｓｉ合金液中直接反应生成直径为０．１－１．０μｍＴｉＣ颗粒，并均匀地分布在α－Ａｌ基体中，晶界上无明显颗粒聚集，制成品性能优异．     

铸造法制备TiC/ZA43复合材料的试验研究

以Ｔｉ,Ａｌ,Ｃ粉末为原料,采用ＸＤ法与铸造法相结合的工艺制备了体积分数为５％的ＴｉＣ／ＺＡ４３复合材料,研究了ＴｉＣ／ＺＡ４３复合材料的铸态组织以及增强相ＴｉＣ颗粒的尺寸与分布。试验结果表明：ＴｉＣ在复合材料中具有良好的稳定性,且随着Ａｌ－ＴｉＣ预制块加入温度的提高,颗粒分布更加均匀,晶粒细化效果更为显著。     

激光熔覆原位合成TiCp/Al复合材料

利用激光熔覆技术,在ＺＬ１０４合金表面原位合成了ＴｉＣｐ／Ａｌ复合材料层。实验结果表明,经２０ｈ混制的Ａｌ－Ｔｉ－Ｃ粉末,在激光熔过程中可以充分反应合成ＴｉＣｐ;在所形成的ＴｉＣｐ／Ａｌ复合材料层中,ＴｉＣ颗粒尺寸细小,约８００ｎｍ;经激光熔覆后的ＴｉＣｐ／Ａｌ复合材料层中ＴｉＣ分布均匀,仅表层在约２００μｍ的ＴｉＣ颗粒富集区和邻近基底部分有２０μｍ的稀释区。     

Al—Ti—C晶粒细化用中间合金的最新进展

对Ａｌ－Ｔｉ－Ｃ晶粒细化用中间合金按Ｔｉ／Ｃ比值归纳成５／１,２０／１和３００／１三种类型进行了评述,认为Ｔｉ／Ｃ比值为２０／１的合金,例如Ａｌ－５％Ｔｉ－０．２５％Ｃ和Ａｌ－３％Ｔｉ－０．１５％Ｃ中间合金为显微组织纯净度与晶粒细化性能的最佳折衷选择。新一代工业用Ａｌ－Ｔｉ－Ｃ中间合金已问世,并在美国铝业公司生产铝合金连铸板材和ＤＣ铸锭时成功地使用了两年。其ＴｉＣ粒子尺寸小于１μｍ,其体积分数比５     

喷射沉积Al-5.5Cu/TiAl3自生复合材料的微观组织及界面结构

采用喷射沉积工艺制备了Ａｌ－５．５Ｃｕ／ＴｉＡｌ３自生复合材料,并对该材料的微观组织及界面结构进行了研究。观察表明ＴｉＡｌ３与α－Ａｌ基体之间存在（０２０）Ａｌ／／（００２）ＴｉＡｌ３,［００１］Ａｌ／／［＾１１０］ＴｉＡｌ３的位向关系,力学性能测试结果表明喷射沉积Ａｌ－５．５Ｃｕ／ＴｉＡｌ３自生复合材料的抗拉强度较铸态的抗拉强度提高约１２％,延伸率提高４５０％,耐磨性则提高１５０％。     

两种Al-Ti-C中间合金的组织和细化效果比较

选取美国某厂生产的Ａｌ－Ｔｉ－Ｃ中间合金与自制的Ａｌ－Ｔｉ－Ｃ中间合金做原料,通过扫描电镜和Ｘ－射线衍射分析及细化试验对Ａｌ－Ｔｉ－Ｃ中间合金的组织分布、相组成和细化效果进行了比较分析。结果表明,两种合金的组织中都有较多的细小ＴｉＣ颗粒,其晶粒平均尺寸为０．３－１．５μｍ,并且自制的Ａｌ－Ｔｉ－Ｃ中间合金的组织分布和细化效果达到国外领先水平。     

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。     

喷射沉积Al—5.5Cu／TiB2自生复合材料的显微组织及性能

研究了采用喷射沉积工艺制得的Ａｌ５．５Ｃｕ／ＴｉＢ２（２０％）自生复合材料的沉积态及挤压态显微组织：沉积态组织细小,颗粒分布均匀,颗粒与基体界面结合良好,很少出现孔洞,原铸态自生组织中呈针片状的ＴｉＡｌ３相消失而呈颗粒状分布,析出相细小弥散;挤压态组织中孔洞基本弥合,纵向组织具有一定方向性,颗粒分布有些不均匀（有一定的条带）。力学性能测试结果表明：喷射沉积后的Ａｌ５．５Ｃｕ／ＴｉＢ２自生复合材料的抗拉强度比铸态提高约５０ＭＰａ,延伸率则提高５００％左右,耐磨性能也有较大提高     

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.