热轧工艺对超纯Cr17铁素体不锈钢成形性能的影响

对一种铌、钛双稳定化的超纯Cr17铁素体不锈钢分别进行常规热轧和低温热轧,再依次进行相同的退火、冷轧及最终再结晶退火处理。对比研究两种热轧工艺对组织、织构演变及成形性能的影响规律。结果表明,与常规热轧相比,低温热轧能显著细化热轧组织、弱化α纤维织构并强化γ纤维织构,最终使冷轧退火板的γ纤维再结晶织构明显增强、偏离{111}<121>组分的程度显著降低,使珋r值增大、△r值减小。低温热轧是改善超纯Cr17铁素体不锈钢成形性能的有效途径。     

连轧和可逆轧工艺对B441铁素体不锈钢成形性能的影响

采用二十辊轧和四连轧两种不同的轧制工艺生产了B441铁素体不锈钢冷轧板,在相同压下率下经相同的退火、酸洗处理,比较了两种冷轧工艺的成品板力学性能,研究了不同轧制工艺下成品板的微观组织和宏观织构。研究了不同轧制方式对B441铁素体不锈钢织构演变和成形性能的影响。结果表明:四连轧在相同退火(990℃保温2 min)下再结晶更容易。四连轧经退火后B441成品板屈服强度、抗拉强度和伸长率均略小于二十辊轧制退火后的成品板。四连轧试样中心层织构主要为{111}112。     

精轧温度对含铌、硼Cr17薄板成形性及表面皱折的影响

通过光学显微镜、X射线衍射及背散射电子衍射技术,研究了精轧温度,即高温精轧和低温精轧,对含Nb、B的超纯Cr17铁素体不锈钢薄板成形性及表面皱折的影响。结果表明：低温精轧有利于得到细小及均匀的冷轧退火组织。低温精轧有利于改善冷轧退火板织构的均匀性,促使冷轧退火板得到均匀、规则的γ纤维再结晶织构并形成更少的取向晶粒簇。因此,低温精轧是显著改善冷轧退火板成形性能及抗皱折性的有效工艺。     

高纯Cr17钢板厚方向织构演变、成形性能及表面皱折

以高纯Cr17铁素体不锈钢为实验材料,对比研究了热轧不退火、退火两种工艺对其板厚方向织构演变、成形性及表面皱折的影响。采用金相显微镜、X射线衍射技术及背散射电子衍射技术观察两种工艺条件下的组织和织构演变。结果表明:成品板各层织构特征存在显著差异,这是由于低温轧制过程中沿板厚方向不同应变状态导致的热轧织构梯度遗传所致。与热轧不退火相比,热轧退火有利于成品板各层γ纤维再结晶织构增强,偏离{111}<112>组分的程度减弱,α纤维织构弱化;有利于弱化成品板的带状晶粒簇,促使晶粒簇分布均匀分散。     

Nb、Ti对铁素体不锈钢铸态及热轧态组织、织构的影响

研究了不同Nb、Ti添加情况下铁素体不锈钢的铸坯组织特征以及热轧后板材的组织和织构.研究结果表明:Nb的添加可以明显细化铸坯组织,而Nb、Ti双稳定元素的添加强烈地促进了铸坯组织晶粒的等轴化和晶粒细化.Nb、Ti元素的加入不仅可以细化铸坯组织,同时也可以细化热轧后的板材组织,单独添加的Nb、Ti元素均可以推迟板材的再结晶过程,Ti的作用更为明显,而Nb、Ti的同时加入可明显推迟板材的再结晶过程.     

超纯铁素体不锈钢织构演变与成形性能的研究

系统研究了超纯铁素体不锈钢(w(Cr)=17%)沿钢板厚度方向各层织构的演变规律和不同精轧温度对织构演变及成形性能的影响规律。采用X射线衍射仪分析了宏观织构演变。研究表明: 热轧及退火后, 钢板表层以剪切织构为主, 中心层由?和?纤维织构组成; 冷轧后, 各层均由较强的?纤维织构和较弱的?纤维织构组成; 冷轧退火后各层均形成?纤维再结晶织构。与高温精轧相比, 低温精轧有利于冷轧退火板?纤维再结晶织构的强化、偏离{111}<112>组分的程度降低, 从而显著改善冷轧退火板的成形性能。     

1Cr17铁素体不锈钢退火工艺与性能的研究

结合现场情况,研究了退火工艺对1Cr17铁素体不锈钢薄带组织、力学性能与成形性能的影响。结果表明:经过退火工艺(860℃×2 min、空冷)处理后,1Cr17铁素体不锈钢薄带再结晶充分,晶粒尺寸细小且均匀;同时提高了1Cr17铁素体不锈钢薄带成形性能的稳定性。     

再结晶退火对超纯铁素体不锈钢抗皱性的影响

为研究超纯铁素体不锈钢的再结晶退火对板材抗皱性的影响,采用拉伸试样表面粗糙度测量、X射线衍射(XRD)和电子背散射衍射(EBSD)技术对再结晶程度不同的板材表层和中心层的起皱程度、显微组织和织构进行了检测分析。结果表明,再结晶程度不同的板材具有不同的表面抗皱性;晶粒细小,尺寸均匀度好的再结晶退火组织有利于提高板材的表面抗皱性;退火钢板中心层再结晶程度较表层深,且起皱严重。分析认为:超纯铁素体不锈钢板材中心层再结晶形成的强点突出的γ纤维织构以及大范围的γ纤维取向团簇是造成板材表面起皱的重要原因;表层由于再结晶程度较弱,形成的γ纤维织构在γ取向线上分布均匀、无明显织构强点,显微组织也较为精细,因此对板材的起皱形貌具有缓解和覆盖的作用。     

中后帮机零部件材料的成形性能控制

研究了中后帮机零部件用铁素体不锈钢的成形性能,分析了Ti元素对冷轧态和退火态铁素体不锈钢的组织与性能的影响,并分析了其作用机理。结果表明,Ti元素的添加可以抑制铁素体不锈钢再结晶晶粒长大,也有利于不锈钢形成γ纤维织构;未添加Ti的不锈钢和添加Ti的不锈钢在0°,45°和90°方向上的硬化指数差别不大,添加Ti的不锈钢强度系数及在同一方向上的塑性应变比要比不添加Ti的不锈钢高;Ti元素的添加在铁素体不锈钢中形成了Ti(N,C)颗粒,可以起到抑制形核和细化再结晶晶粒的作用。     

纤维织构份额对430铁素体不锈钢表面起皱的影响

通过工艺控制得到含不同-纤维织构份额的430铁素体不锈钢样品,研究了-纤维织构份额对430不锈钢表面起皱程度的影响。结果表明：将冷轧430铁素体不锈钢在略低于再结晶温度下长时间保温,然后进行高温再结晶退火处理能够获得高份额的-纤维织构;随着显微组织中-纤维织构份额的提高,430铁素体不锈钢表面抗起皱性能增强。相比于{100}<011>和{112}<110>取向晶粒,-纤维取向晶粒平均塑性应变比高,并能在再结晶组织中较少形成取向相近的晶粒簇,减轻了铁素体不锈钢的表面起皱现象。     

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.