低碳锰钢魏氏组织的形成及力学性能

研究了低碳锰钢魏氏组织形成规律。在奥氏体化温度为９００－１３００℃，以适当速度冷却，可产生魏氏组织。说明魏氏组织并非过热标志。在同一奥氏体温度下，有魏氏组织的试样韧度高于无魏氏组织的，魏氏组织的针状铁素体对强韧性有利。     

两段式冷却对C-Mn钢奥氏体中温转变的影响

采用Formastor全自动相变仪进行了两段式冷却条件下C-Mn钢的热膨胀试验,并结合组织观察和显微硬度测量,研究了冷却速度以及发生部分先共析铁素体转变对奥氏体中温转变的影响。结果表明:随着冷却速度的增大和先共析铁素体含量的增加,贝氏体相变开始温度和结束温度均降低,贝氏体转变量减少;奥氏体随冷却速度的增大,转变产物由铁素体+珠光体逐渐变为魏氏组织铁素体+珠光体、网状铁素体+魏氏组织+贝氏体、马氏体的趋势;而对已发生部分先共析铁素体转变的过冷奥氏体,随先共析铁素体含量的减少,组织由魏氏组织+贝氏体向魏氏组织+马氏体转变。     

魏氏组织在27SiMn钢管中的形成条件

研究了27SiMn钢管中魏氏组织(W)的形成条件及其对力学性能的影响.结果表明,魏氏组织(W)的形成与加热温度、冷却速度、碳含量以及奥氏体(A)晶粒的大小有关.魏氏组织(W)出现后,由于粗大的奥氏体(A)晶粒使钢的冲击韧性显著降低,因而使钢变脆.     

合金渗碳钢正火时铁素体形态的控制

选用20CrMoH钢汽车齿轮毛坯,模拟锻(轧)后产生粗大奥氏体晶粒的奥氏体化加热温度,采用不同冷却工艺,控制钢件等温处理和之前连续冷却时的铁素体转变过程,以确保产品正火质量.结果表明,20CrMoH钢锻(轧)毛坯原奥氏体晶粒虽然比较粗大,但通过控制冷却调整铁素体的形态,不仅可避免生成魏氏组织,还可以提高产品质量,实现组织均匀,力学性能稳定.     

奥氏体化温度对等温淬火球墨铸铁摩擦磨损性能的影响

奥氏体化处理是得到高性能等温淬火球墨铸铁(Austempered ductile iron, ADI)的关键步骤，通过奥氏体化处理，铸铁基体组织向奥氏体转化，为后续的等温淬火处理过程中奥氏体向奥铁体的相变提供前驱体。对奥氏体化温度进行调控，研究了ADI微观组织的相应变化及其对力学性能、摩擦磨损性能的影响。研究发现，奥氏体化温度的提高使石墨向基体的渗碳作用增强，奥氏体碳含量增加、稳定性增强，一方面导致奥氏体在冷却转变过程中铁素体的形核驱动力降低，奥铁体组织中铁素体形态更细长，另一方面导致块状残留奥氏体增多、碳含量提高，使材料强度、硬度及断后伸长率均发生下降。较高的奥氏体化温度使ADI含有大量高碳残留奥氏体，导致其在摩擦磨损过程中难以通过应力诱发相变形成马氏体来提升耐磨性。综合力学及摩擦磨损性能，ADI的奥氏体化温度应不大于950℃。     

45钢手柄轴的淬火开裂及其预防

45钢制手柄轴,由于其直径是对淬火开裂敏感的尺寸,加之有网状铁素体和魏氏组织等原材料缺陷．淬火时常常开裂。采取正火处理和适当降低奥氏体化温度及预冷淬火等措施,取得了防止手柄轴淬裂的令人满意的效果。     

固溶温度对ZG0Cr26Ni5Mo2N铸造双相不锈钢组织的影响

针对相比例控制的技术难点,以双相不锈钢OCr26Ni5Mo2N为基础,通过对铸造OCr25Ni5Mo2N双相不锈钢进行系列温度固溶处理,研究了固溶温度对铸造双相不锈钢组织的影响.研究结果表明:1)当固溶温度在980～1120℃时,随着固溶温度的提高,OCr25Ni5Mo2N钢中的铁素体相含量几乎呈直线上升.2)采用980～1120℃进行固溶处理时,铁素体基体上分布的长条状、块状和魏氏组织形态的奥氏体的原有尖角边界逐渐钝化,奥氏体本身分解、球化,弥散分布在铁素体基体上,固溶处理温度越高,奥氏体分解、球化程度越高.     

10Ni5CrMoV钢的组织遗传规律及其消除工艺研究

对10Ni5CrMoV钢奥氏体化温度对晶粒尺寸的影响及奥氏体自发再结晶的基本规律作了研究。结果表明：奥氏体化晶粒急剧粗化的临界温度为1200℃；奥氏体自发再结晶的最低温度 为850℃；900℃以下奥氏体自发再结晶以形成针状奥氏体和球状奥氏体两种方式进行；二次加热时，加热温度低于900℃时都有组织遗传发生。加热温度在900℃以上时，再结晶奥氏体为球形，无组织遗传发生。加热温度超过950℃以上，细化了的奥氏体晶粒开始粗化；620－880℃等温退火＋950℃淬火具有很好的细化效果。     

亚共析钢中α铁的魏氏组织

试验证明亚共析钢中魏氏组织的α铁系以贝茵体型相变的机构形成,相当于无碳贝茵体。奥氏体晶粒尺度、碳含量、温度以及冷却速度对魏氏组织的影响都很容易根据贝茵体形成机构的理论加以解释。     

THE MECHANISM OF FORMATION OF WIDMANST(A

试验证明亚共析钢中魏氏组织的α铁系以贝茵体型相变的机构形成,相当于无碳贝茵体。奥氏体晶粒尺度、碳含量、温度以及冷却速度对魏氏组织的影响都很容易根据贝茵体形成机构的理论加以解释。     

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.