TiCp／Ti复合材料的熔铸法制备及微观组织研究

用熔铸法制备了原位自生钛合金基复合材料,为减少复合材料的成分波动,熔炼前先用混合均匀的TiC粉和铝制备TiCp-Al中间合金,然后用中间合金制取复合材料,研究了复合材料中TiC的形貌。结果表明所制备的复合材料的成分易控制,波动小。对其TEM的研究表明,其TiC形态为初生树枝晶和短棒状共晶。此外还发现在0．3-0．6μm的规则块状TiC颗粒析出,多分布在晶界上,与其体界面干净,无反应层,HRTEM也证明不存在反应层。基体中存在较多位错,且位错线上有阻碍位错运动的TiC析出物。     

TiC_P/Ti复合材料的熔铸法制备及微观组织研究

用熔铸法制备了原位自生钛合金基复合材料。为减少复合材料的成分波动 ,熔炼前先用混合均匀的TiC粉和铝粉制备TiC Al中间合金 ,然后用中间合金制取复合材料。研究了复合材料中TiC的形貌。结果表明所制备的复合材料的成分易控制 ,波动小。对其TEM的研究表明 ,其TiC形态为初生树枝晶和短棒状共晶 ,此外还发现有 0 3～ 0 6 μm的规则块状TiC颗粒析出 ,多分布在晶界上 ,与基体界面干净 ,无反应层 ,HRTEM也证明不存在反应层。基体中存在较多位错 ,且位错线上有阻碍位错运动的TiC析出物 ,。     

TiC/2014复合材料的制备和力学性能研究

采用自蔓延高温合成法 (SHS)制备了 3 0 %TiC/Al中间合金 ,再以 2 0 14铝合金作为基体 ,利用搅拌铸造法加入一定量的中间合金制备 5 %TiC/ 2 0 14铝基复合材料 ,并研究了中间合金中相组成以及TiC颗粒的加入对复合材料力学性能的影响。研究表明 ,采用SHS技术制备的中间合金中只形成尺寸细小、排列紧密的TiC颗粒 ,TiC颗粒的加入可以提高TiC/ 2 0 14复合材料的力学性能 ,尤其是高温性能。     

TiC颗粒增强钛基复合材料的形变

研究了TiC颗粒增强钛基复合材料增强颗料和基体之间的不均匀形变,得出颗粒和基体之间的形变过程中产生形变摩擦阻力,通过弹塑性力学计算出的TiC/Ti界面上颗粒阻碍基体变形力为TiC强度的0．6倍,阻碍基体中滑移的进行,使基体得到强化。另一方面,当界面上的形变应力同基体的某个晶面形成位错源时,可放出位错环,使应力得到释放,同时增加基体的位错密度,位错互相缠绕形成胞状亚结构,强化基体。     

原位反应法制备Fe-Cr-Ni/TiC(p)复合材料的组织结构与抗氧化性

利用原位反应法制备了Fe-26Cr-14Ni+3 mass%TiC(p) 和Fe-26Cr-14Ni+6 mass%TiC(p)复合材料.复合材料由平均尺寸为05～5 μm的TiC颗粒与 γ基体组成，TiC中存在α/2［11〖DD(〗-〖DD)〗0］和α/2［01〖DD(〗-〖DD)〗1］型高 密度位错，TiC颗粒与γ相间界面为共格界面，二者存在下列位向关系：(2〖DD(〗-〖DD)〗 20)TiC∥(020)γ，［001］TiC‖［001］γ.1473K下的抗氧化性实验结 果表明，TiC颗粒的存在使复合材料的初始氧化阶段具有短路扩散效应，两种复合材料的氧 化动力学曲线分别符合抛物线和对数增长规律，在稳定氧化阶段，复合材料比基体合金具有 更优良的抗氧化性能，氧化膜主要由多面体状Cr2O3和FeCr2O4相构成.     

铸造Fe/TiCp复合材料的显微组织和力学性能

通过感应熔炼铸造法制备了一种Fe／TiCp复合材料，采用X-射线衍射、光镜和扫描电镜及能谱分析研究了其铸态和850℃退火态的显微组织和力学性能。结果表明：铸态复合材料的显微组织由珠光体基体和均匀分布的立方状TiC颗粒组成，TiC颗粒与基体界面洁净，抗拉强度817MPa，伸长率2．8％，硬度33．2HRC；经850℃退火后，基体转变为铁素体和珠光体，TiC颗粒形貌基本不变，强度和硬度较铸态有所降低，伸长率略有升高。     

铝热快速凝固工艺合成高强TiC/FeNiCr复合材料

采用铝热快速凝固工艺制备了FeNiCr合金及TiC／FeNiCr复合材料，利用光学显微镜、扫描电镜、X射线衍射等手段研究了该复合材料的显微组织和相结构，测量了复合材料的压缩强度。结果表明，TiC／FeNiCr复合材料由TiC陶瓷增强相和α-Fe合金基体组成。TiC／FeNiCr复合材料组织细小，TiC呈多边形均匀分布在合金基体中，晶粒尺寸约为2～3μm。TiC对FeNiCr基体具有很好的晶粒细化及强化作用，TiC／FeNiCr的压缩断裂强度及形变率分别为2760MPa及25％，远大于FeNiCr合金及部分Fe基非晶材料。     

TiC／Al-4．5Cu原位复合材料的相结构特征

采用熔体接触反应法制备了TiC／Al-4．5Cu复合材料,通过光学显微镜、透射电镜等,对TiC颗粒增强Al-4．5Cu原位复合材料的相结构进行分析。结果表明,5％TiC／Al-4．5Cu原位复合材料的主要增强相为TiC;TiC弥散分布在α-Al基体中,与基体结合良好且界面光滑。在5TiC／Al—4．5Cu原位复合材料中TiC呈球形或近球形,颗粒细小,其尺寸约为0．1～0．5μm;而在5％TiC／Al—4．5Cu—XMg原位复合材料中TiC呈规则六边形,颗粒较大,其尺寸约为0．5～0.8μm。     

TiCp／1Cr18Ni9复合材料显微组织和力学性能的研究

采用原位合成铸造法制备了TiC颗粒增强1Cr18Ni9钢基复合材料。试验结果表明：TiC颗粒在基体中分布均匀，与基体结合良好且无团聚现象，复合材料的室温、高温强度与基体相比均有提高，但塑性和冲击韧性有所下降。     

原位反应法制备Al2O3-TiC/Al复合材料

通过向含Ti的Al-Si合金熔体中通入CO2气体制备Al2O3-TiC／Al复合材料的方法．研究了Al2O3-TiC／Al复合材料特性。用X射线衍射仪（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对复合材料的组织进行了研究。研究表明，CO2与合金熔体中的Al、Ti原位反应生成Al2O3和TiC颗粒，Al2O3和TiC颗粒尺寸在0．2～1．0μm之间，均匀分布在基体中，反应生成的Al2O3和TiC颗粒数量与CO2的通入时间有关。     

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.     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.