20MnCrNi2MoRE钢贝氏体回火过程

针对20MnCrNi2MoRE低合金耐磨铸钢,采用洛氏硬度计、扫描电镜和透射电镜观察分析其在200~650℃范围内的回火转变过程。结果表明,20MnCrNi2MoRE钢铸态组织为粒状贝氏体,200℃回火时,贝氏体铁素体条首先发生变化,500℃回火时,在贝氏体铁素体条内、晶界及位错处观察到有碳化物析出。300℃回火时观察到(M/A)岛发生分解,650℃回火时(M/A)岛已经完全分解。低于500℃回火时,硬度变化不大,500℃以上回火时,由于位错密度降低和碳化物聚集长大,使硬度显著降低。     

稀土低合金贝氏体耐磨铸钢回火过程中的组织演变

针对添加镧铈混合稀土的20MnCrNi2Mo低合金贝氏体耐磨铸钢,将其铸态组织分别加热到200~650℃并保温1 h进行回火处理,采用扫描电镜和透射电镜观察回火过程中的显微组织,采用物理化学相分析方法对析出相进行定性与定量分析,采用X射线衍射仪对不同温度回火组织中残留奥氏体量进行定量测定,分析回火过程中的组织演变。结果表明,实验钢的铸态组织为粒状贝氏体,回火过程中析出的平衡相碳化物为合金渗碳体,且其中有微量稀土固溶;500℃回火时未观察到明显的回复现象,650℃回火时有亚晶形成,发生明显的回复;200℃回火时M/A岛基本未发生分解,随回火温度的升高,M/A岛逐渐发生分解,到450℃回火时,M/A岛大量分解。     

贝氏体组织的回火转变

研究贝氏体组织的回火转变具有重要理论意义和工程应用价值。贝氏体回火时将发生一系列的转变,贝氏体铁素体中形成碳原子偏聚区,析出碳化物,发生回复,内应力将消除。回火温度升高时,碳化物在位错线处形核-长大,发生聚集球化。在400℃以上回火时,残留奥氏体发生分解。M/A岛也发生转变。回火产物为回火托氏体。     

回火温度对15Cr2Ni3MoW钢组织与力学性能的影响

观察了15Cr2Ni3MoW钢在200～600℃区间回火处理后的力学性能和组织变化。结果表明,该钢经350℃回火后出现大量稳定化的M/A岛,在500～550℃回火后M/A岛大量分解,析出的碳化物沿晶界连续分布,出现了回火脆性。试验获得的最佳回火工艺为:350℃回火3h后空冷,该工艺可使15Cr2Ni3MoW钢的屈服强度提高37%,冲击韧性提高50%。     

回火工艺对铌钛低碳贝氏体钢组织与性能的影响

通过光学显微镜、透射电镜和力学性能检验,研究了回火温度对TMCP型铌钛微合金化低碳贝氏体钢微观组织结构、第二相析出及力学性能的影响。结果表明,回火后力学性能非单调变化,归因于铌钛微合金化钢在回火过程中,贝氏体内位错亚结构回复软化与第二相析出强化及碳的脱溶机制综合作用。400～500℃回火,Nb、Ti第二相持续析出强化,随回火温度的升高,板条贝氏体回复作用逐渐加强并逐渐达到回复稳定状态。回火温度≥500℃时,M/A岛组织发生分解,贝氏体板条合并、组织粗化,析出相聚集长大,固溶元素脱溶,组织演变为贝氏体和铁素体,强度持续降低,但韧塑性得到改善。550℃回火后钢板具有最佳综合力学性能:抗拉强度为790 MPa,屈服强度为740 MPa,伸长率为16.5%,-20℃冲击吸收能量为250 J。     

回火温度对一种Fe-Cr-Ni-Mo高强钢碳化物及其力学性能的影响

利用TEM和三维原子探针(3DAP)研究了一种Fe-Cr-Ni-Mo高强钢中碳化物随回火温度的变化及其对力学性能的影响.结果显示,回火温度较低(400℃)时,钢中析出M3C合金渗碳体及M7C3合金碳化物,M为Fe,Cr和Mn的组合,其中M3C长度约为1μm,而M7C3尺寸较小,小于200 nm;回火温度较高时(500和600℃),碳化物析出数量增加,但M3C合金渗碳体尺寸变小,数量减少甚至不出现,同时析出尺寸较小的M2C和M6C(小于200 nm);继续提高回火温度(650℃),除M2C外还出现MC型碳化物,其尺寸小于100 nm,析出数量减少.合金碳化物M2C,M6C和MC的合金元素主要以V,Cr和Mo为主.高强钢的强度随回火温度的升高而下降,但在500~600℃回火温度区间,由于V碳化物析出会引起二次硬化效果,强度下降不明显,因此实验钢在530~600℃内回火后可获得较好的强韧性配合.     

添加稀土的20MnCrNi2Mo耐磨铸钢的组织与性能

针对添加镧、铈混合稀土的20MnCrNi2Mo耐磨铸钢,采用扫描电镜、透射电镜、洛氏硬度计、电子万能试验机和电子式摆锤冲击试验机进行组织观察和和力学性能测定,并分析试验钢显微组织和力学性能的关系。结果表明：添加镧、铈混合稀土的20MnCrNi2Mo耐磨铸钢铸态组织为粒状贝氏体,且存在较高密度位错;稀土含量为0.0092%的20MnCrNi2Mo耐磨铸钢硬度达到32.11 HRC,抗拉强度为1128.48 MPa,冲击吸收能量(-40 ℃)为9.887 J。高密度位错能提高试验钢的硬度,但不利于塑性的改善;贝氏体组织中的(M/A)岛对于硬度和强度的提高有利,但会降低韧性;添加稀土元素使夹杂物变质,有助于改善韧性。     

A508-3钢回火过程的组织演变及动力学分析

回火对核电设备用A508-3钢的力学性能影响很大。采用扫描电镜和硬度测试研究了A508．3钢回火过程中组织的演变和性能的变化,并对经600～660℃回火的钢进行了基于硬度测量的动力学分析。回火过程中硬度的变化可以用残留奥氏体和奥氏体一马氏体的分解,贝氏体铁素体内碳化物的析出、粗化以及贝氏体铁素体的回复再结晶来解释。动力学分析表明,A508．3钢在600～660℃回火时的相变激活能约为101．4kJ／mol,与碳原子在铁素体中的扩散激活能相近。A508．3钢只有在较高温度回火时,才出现贝氏体铁素体内碳化物的大量析出和粗化,这说明该钢种具有较好的回火稳定性。     

18Cr2Ni4WA钢粒状贝氏体和粒状组织于高温回火过程中碳化物的析出规律

本文研究了18Cr2Ni4WA钢粒状贝氏体和粒状组织在高温回火过程中碳化物的析出及转变规律。结果表明,在485～550℃M岛已明显分解,575～800℃BF和MF亚晶界处开始析出碳化物,A岛经二次高温回火转变为α+K。最初析出的碳化物为M_6C型,后随时间的延长发生转变,其转变规律为M_2C→M_(23)C_6→M_4C。     

Mo含量及冷却工艺对低碳贝氏体钢组织与M/A岛的影响

为考察冷却工艺参数对低碳贝氏体钢组织和马氏体/奥氏体(M/A)岛的影响,利用热模拟试验机对不同Mo含量的低碳贝氏体钢进行研究。结果表明,随Mo含量增加,组织中板条贝氏体和M/A岛含量增多;增大冷速、降低终冷温度均能够细化组织,提高组织中板条贝氏体的含量及显微硬度;随着冷速的升高,M/A岛含量减少,由大颗粒的球形向细小的针状转变;终冷温度在410~350℃时,M/A岛含量和尺寸随终冷温度的降低逐渐减小,终冷温度降为330℃时,组织中短棒状M/A岛数量增多,M/A岛含量也开始增多。组织中的粒状贝氏体+板条贝氏体和其上分布的尺寸细小、形状规则的M/A岛是获得实验钢强度和韧性良好匹配的最佳组织类型。     

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.     

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。