表面微观屈服强度与疲劳极限的关系SCIEI

本文利用X射线对不同碳含量钢的表面微观屈服强度进行了研究。试验结果表明,表面微观屈服强度σ_(ms)远低于整体材料的屈服限,是一个反映表面抵抗塑性变形能力大小的参量。材料光滑疲劳极限往往是由裂纹荫生所控制的,与表面抵抗塑性变形的能力有关。本试验表明不同材料的σ_(ms)与存活率为50％疲劳极限的关系为:σ_(ms)=(0.81—1.02)σ_(-1);40Cr不同热处理状态的σ_(ms)与存活率为99.9％疲劳极限的关系为:σ_(ms)=(0.98—1.10)σ_(-1)。σ_(ms)的测定要比疲劳极限σ_(-1)的测定省时得多,有可能在工程上获得应用。     

长时高温运行后1Cr18Ni12Ti奥氏体钢组织变化

采用金相显微镜、扫描电镜和X射线衍射仪对1Cr18Ni12Ti奥氏体不锈钢管断口和显微组织中的析出相进行了分析,研究了导致材料脆化的原因、晶界和晶内析出相的结构以及析出相对材料性能的影响.结果表明,1Cr18Ni12Ti奥氏体不锈钢脆化是由于材料发生过时效,组织结构发生劣化的结果,主要表现为晶界出现连续和封闭的碳化物析出相,晶内析出针状σ相.这种组织结构的出现一方面阻止位错的运动和破坏变形的连续性,也使晶界附近组织贫铬化,导致材料的韧性、抗氧化和腐蚀性、甚至强度和高温持久性能下降.     

加工工艺对0Cr18Ni10Ti不锈钢管高温拉伸性能的影响

文章研究了拉拔变形量、固溶温度及矫直次数对0Cr18Ni10Ti不锈钢管320℃高温拉伸性能的影响。结果表明:随着拉拔变形量的增大,0Cr18Ni10Ti不锈钢管的屈服强度和抗拉强度明显降低,延伸率显著升高;随着固溶温度的升高,0Cr18Ni10Ti不锈钢管抗拉强度先升高后降低,屈服强度升高,延伸率降低;随着矫直次数的增加,0Cr18Ni10Ti不锈钢管的高温抗拉强度先降低后变化不大,高温屈服强度略有升高,延伸率变化不大。     

变形速率对GH3625合金弹-塑性变形行为的影响

利用原位中子衍射室温压缩实验、EBSD和TEM等手段研究了变形速率对GH3625合金弹-塑性变形行为的影响。结果表明，GH3625合金宏观应力-应变曲线包括弹性变形阶段（施加应力σ≤300 MPa）、弹-塑性转变阶段（300 MPa<σ≤350 MPa）和塑性变形阶段（σ>350 MPa），这与细观晶格应变行为一致。同时，变形速率与晶体弹性和塑性各向异性密切相关。通过特定hkl反射的晶格应变、峰宽和强度的研究结果表明，变形速率对晶体弹性各向异性影响较小，而对晶体塑性各向异性影响较大。随变形速率的增加，大角度晶界逐渐向小角度晶界转变，孪晶界的比例逐渐减小，晶粒由均匀变形向不均匀变形转变。随变形速率的增加，合金的总位错密度（ρ）先减小后增加，而几何必须位错密度(ρ^GND)单调递增，统计存储位错密度(ρ^SSD)单调递减；同时，试样在变形速率为0.2 mm/min时表现出反常的加工硬化行为，这主要与均匀变形产生的统计储存位错（SSD）有关；此外，位错强化贡献和TEM观察证实了GH3625合金的塑性变形机制以位错滑移为主，其加工硬化机制是位...     

粒状组织和粒状贝氏体的残余应力与屈服强度表达式

用18Cr2Ni4WA钢研究了粒状组织和粒贝的残余应力与屈服强度表达式。结果表明,粒状组织和粒贝形成过程中造成很大的残余应力,在其屈服强度表达式中必须考虑该残余应力的影响,其表达式为: σ_(0.2)=(1-V_(M-A))(σ_(So) σ_(SS) σ_V σ_D σ_G σ_(SG)-100V_(Mσ_(M(S))) V_(M-A)(σ_(So) σ_(SS) σ_V σ_D)     

微尺度Ti-10V-2Fe-3Al单晶压缩变形行为及其微观机制

研究了尺寸为0.3~2.0μm的Ti-10V-2Fe-3Al(Ti1023)微柱沿[011]位向压缩的变形行为及微观机制.结果表明:Ti1023微柱沿[011]位向压缩的塑性变形阶段应力-应变曲线光滑,表现出持续加工硬化,无应变突发现象.微柱屈服强度(σ_(0.2))随试样尺寸(d)的减小而增加,其关系为:σ_(0.2)∝d~(-0.18).微柱塑性变形以{112}111滑移主导,应变量超过10%时产生应力诱发马氏体(a″),应力诱发马氏体相变发生时的应力(σ_(cm))亦随d的减小而增加,其关系为:σ_(cm)∝d~(-0.28).在均匀塑性变形阶段,应变硬化指数(n)随尺寸的减小而增加.采用TEM观察了变形前后微观组织形貌,表明Ti1023微柱沿[011]位向压缩时表现出来的持续应变硬化归因于晶体中纳米尺度w相和a″对位错滑移的阻碍作用.     

Fe-0.04Nb-0.02C合金的强化

Fe-0.04Nb-0.02C合金经1175—900℃轧制并随即在600℃等温处理后,获得直径为7—22微米等轴细晶粒的α-Fe。在α-Fe中保留相当数量的三维和二维位错网络,并沉淀析出细小的NbC粒子。通过细化晶粒,NbC第二相粒子和位错亚结构的综合强化,合金下屈服强度可提高到35—38公斤/毫米~2。下屈服强度σ_(1y)与晶粒的平均直径d之间的关系符合Hall-Petch公式: σ_(1y)=σ_i+k_yd~(-(1/2)) 其中k_y=2.2公斤/毫米~(3/2);对于600℃等温30秒,40分及3小时者,σ_i分别为21.5,13.5及13.5公斤/毫米~2。理论计算结果表明,σ_i值是NbC第二相粒子弥散强化,位错亚结构强化和点阵阻力对屈服强度贡献σ_p,σ_d和σ_1的叠加,即σ_i=σ_p+σ_d+σ_1 合金的位错密度随拉伸变形程度的增高而增加。平均位错密度ρ与对应的流变应力值σ_f的关系可表达成下式σ_f=σ_0+αGbρ~(1/2) 其中α=0.37;σ_0是除位错交互作用外其他因素对流变应力的贡献,对于600℃等温30秒,40分和3小时者,σ_0分别为34,30及30公斤/毫米~2。在α-Fe中沉淀析出的NbC粒子周围观察到“沉淀生长”位错圈,对其形成机理进行了分析,它们的强化作用尚需进一步探明。     

STRENGTHENING OF THE Fe-0.04Nb-0.02C ALLOY

Fe-0.04Nb-0.02C合金经1175—900℃轧制并随即在600℃等温处理后,获得直径为7—22微米等轴细晶粒的α-Fe。在α-Fe中保留相当数量的三维和二维位错网络,并沉淀析出细小的NbC粒子。通过细化晶粒,NbC第二相粒子和位错亚结构的综合强化,合金下屈服强度可提高到35—38公斤/毫米~2。下屈服强度σ_(1y)与晶粒的平均直径d之间的关系符合Hall-Petch公式: σ_(1y)=σ_i+k_yd~(-(1/2)) 其中k_y=2.2公斤/毫米~(3/2);对于600℃等温30秒,40分及3小时者,σ_i分别为21.5,13.5及13.5公斤/毫米~2。理论计算结果表明,σ_i值是NbC第二相粒子弥散强化,位错亚结构强化和点阵阻力对屈服强度贡献σ_p,σ_d和σ_1的叠加,即 σ_i=σ_p+σ_d+σ_1 合金的位错密度随拉伸变形程度的增高而增加。平均位错密度ρ与对应的流变应力值σ_f的关系可表达成下式 σ_f=σ_0+αGbρ~(1/2) 其中α=0.37;σ_0是除位错交互作用外其他因素对流变应力的贡献,对于600℃等温30秒,40分和3小时者,σ_0分别为34,30及30公斤/毫米~2。 在α-Fe中沉淀析出的NbC粒子周围观察到“沉淀生长”位错圈,对其形成机理进行了分析,它们的强化作用尚需进一步探明。     

冷变形对0Cr18Ni10Ti不锈钢管拉伸性能的影响

研究了经冷拉拔预变形后0Cr18Ni10Ti不锈钢管的室温和320 ℃拉伸性能及其断口形貌特征。结果表明,随着冷变形加工率的增大,0Cr18Ni10Ti不锈钢管室温和320 ℃抗拉强度和屈服强度增大,断后伸长率减小;钢管320 ℃拉伸性能较室温有所下降,其中断后伸长率下降明显。拉伸断口观察表明不锈钢管室温和高温拉伸断口均呈韧性断口特点,320 ℃拉伸断口较室温断口韧窝密度降低,尺寸增大。     

新型Cr18Ni9NbTiN奥氏体不锈钢的高温蠕变行为

采用RDL100型电子高温蠕变试验机测试了新型Cr18Ni9NbTiN奥氏体不锈钢在650 ℃不同应力下的蠕变性能。利用SEM、TEM及EDS等观察分析了220 MPa下不同蠕变阶段的组织形貌。结果表明,蠕变初期,晶内位错密度急剧增加,位错发生缠结,晶内有细小的NbN相弥散析出;稳态蠕变阶段,位错形成网状结构,晶内有TiN颗粒析出,链状(Cr, Fe)23C6沿晶界析出,位错网和析出的第二相共同降低了位错可动性,改善了合金抗蠕变性能;加速蠕变阶段,大量扩展位错出现,延长了蠕变寿命。Cr18Ni9NbTiN钢蠕变断裂属于沿晶脆性断裂,晶界处发现部分(Cr, Fe)23C6剥落,三叉晶界处发现楔形裂纹。     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。