时效温度对HSLA100钢组织与性能的影响

研究了HSLA100钢轧态及时效过程中组织与力学性能的变化.结果表明:HSLA100钢轧态组织为高密度位错的板条贝氏体,板条间分布着少量M-A岛.经450℃时效处理后,大量球状ε-Cu相沉淀析出,此时钢板屈服和抗拉强度最高,而-40℃冲击功最低.在450～720℃时效时,随时效温度升高,高密度板条贝氏体发生回复,ε-Cu相粗化成短棒状,屈服强度连续下降,但在650℃时效时仍达到760 MPa的较高水平;抗拉强度在650℃时达到最低值后小幅上升:-40℃冲击功持续升高至700℃附近达到峰值.钢质纯净度是影响HSLA100钢低温韧性的一个主要因素,虽然通过升高时效温度可在一定程度上提高钢的低温冲击韧度,但增幅有限.     

Cu的时效行为及其对0Cr14Ni5Mo2Cu2Nb钢性能的影响

研究了不同时效温度下的沉淀硬化不锈钢0Cr14Ni5Mo2Cu2Nb的TEM组织、硬度和冲击韧性.结果表明时效过程中,0Cr14Ni5Mo2Cu2N钢主要以ε-Cu相析出为主.时效温度为420℃时,Cu以细小共格ε-Cu相析出,导致0Cr14Ni5Mo2Cu2N钢的硬度达到峰值,而韧性最差,冲击断口以解理为主.随着时效温度增加,ε-Cu相逐步脱溶长大,基体再结晶,硬化程度逐步降低,韧性升高,冲击断口逐步过渡为全韧窝形貌.0Cr14Ni5Mo2Cu2Nb钢的韧性主要决定于冲击裂纹扩展功.时效组织对0Cr14Ni5Mo2Cu2Nb钢冲击裂纹形成功影响较小,对裂纹扩展功有着较大影响.     

Cu的时效行为及其对0Cr14Ni5Mo2Cu2Nb钢性能的影响

研究了不同时效温度下的沉淀硬化不锈钢0Cr14Ni5Mo2Cu2Nb的TEM组织、硬度和冲击韧性.结果表明:时效过程中,0Cr14Ni5Mo2Cu2N钢主要以ε-Cu相析出为主.时效温度为420℃时,Cu以细小共格ε-Cu相析出,导致0Cr14Ni5Mo2Cu2N钢的硬度达到峰值,而韧性最差,冲击断口以解理为主.随着时效温度增加,ε-Cu相逐步脱溶长大,基体再结晶,硬化程度逐步降低,韧性升高,冲击断口逐步过渡为全韧窝形貌.0Cr14Ni5Mo2Cu2Nb钢的韧性主要决定于冲击裂纹扩展功.时效组织对0Cr14Ni5Mo2Cu2Nb钢冲击裂纹形成功影响较小,对裂纹扩展功有着较大影响.     

AMS 6308钢中Cu的析出强化

研究了AMS 6308钢在不同温度回火过程中Cu的强化机制及其对力学性能的影响。结果表明,150~350℃回火,AMS6308钢的组织为回火马氏体,强度和硬度略有增加,韧性下降。400~450℃回火,强度和硬度逐渐增加,这是由大量细小(10 nm)的ε-Cu相在基体内和位错线上析出造成。450℃回火,ε-Cu相析出数量显著增加,导致强度和硬度达到峰值,韧性最差。450℃以上回火,随温度提高,ε-Cu相长大粗化,析出数量减少,其形态由球状转变为棒状或短杆状,沉淀强化作用减弱,M6C碳化物长大,基体发生回复再结晶,强度和硬度显著下降,韧性逐渐提高。     

17-4PH不锈钢热处理工艺

介绍了不同的热处理工艺对17-4PH马氏体沉淀硬化不锈钢力学性能及组织的影响,对其沉淀硬化机理进行了总结和探讨。17-4PH不锈钢兼有强度高、耐蚀性好的优点。传统的工艺为固溶+时效处理,普遍采用的固溶温度为1040℃,随着时效温度的提高和时效时间的延长,其强度和硬度升高,塑韧性降低。在传统工艺的基础上,增加调整处理,可以细化马氏体基体组织,提高材料的韧性及耐蚀性。对于17-4PH钢的强化机理,普遍认为与ε-Cu的析出有关,但对于其形貌的分析不尽相同。     

690MPa级海洋平台用钢的组织和性能

根据测出的CCT曲线制定了690 MPa级海洋平台用钢的轧制工艺,研究了试验钢低碳贝氏体钢回火前后组织对性能的影响.研究了Cu在650 ℃的时效行为及其时效硬化规律.结果表明,650 ℃回火1 h后试验钢的屈服强度达到780 MPa以上,伸长率达到18.5%,-60℃冲击功达到81 J;由于ε-Cu的析出在45 min时效时出现硬度峰,大量 Cu相在位错线、板条界及铁素体内析出,尺寸在40～50 nm,有强烈沉淀强化作用,随着时效时间的延长,沉淀强化作用减弱.     

S30432耐热钢650℃时效的组织和力学性能

研究了S30432耐热钢在650 ℃时效时的微观组织和力学性能,特别探讨了S30432钢时效过程中析出相的变化对力学性能的影响.结果表明,实验合金时效初期ε-Cu和M23C6大量析出,随后逐渐长大,其中M23C6尺寸较大且粗化较快,但ε-Cu长期时效后尺寸依然细小.时效初期硬度升高的主要原因是ε-Cu的析出,长期时效过程中ε-Cu尺寸保持细小是硬度稳定在较高水平的主要原因.此外,时效初期由于M23C6大量析出冲击韧性急剧下降,随后M23C6的粗化是冲击韧性继续下降的主要原因.     

时效温度对S17400不锈钢的显微组织和力学性能的影响

对S17400不锈钢进行了1 040℃、油冷的固溶处理,随后在495～650℃时效处理。检测了钢的显微组织和力学性能。结果表明:在495℃时效处理的S17400不锈钢的组织为马氏体、析出相ε-Cu和NbC,在635℃时效处理的钢有二次马氏体形成;在495～635℃时效时,随着时效温度的提高,钢的强度降低,冲击韧度提高。此外,650℃时效的钢强度性能高于冲击韧度低于635℃时效的钢。     

高韧性不锈钢FV520(B)的析出硬化行为研究

研究了350、420、470、520、560、600、630℃时效温度下沉淀硬化不锈钢FV520(B)的TEM组织、硬度和示波冲击韧度。结果表明:时效过程中,FV520(B)钢主要以富铜相-εCu析出为主。硬度在420℃时效出现峰值,而韧性最差,主要与组织中细小富铜相共格析出有关。随着时效温度增加,富铜相逐步脱溶长大,基体再结晶,硬化程度逐步降低。FV520(B)钢的韧性主要决定于冲击裂纹扩展功。时效组织对FV520(B)钢冲击裂纹萌生功影响较小,对裂纹扩展功有着较大的影响。     

时效处理对极低碳针状铁素体钢组织和力学性能的影响

利用光学显微镜、扫描电镜和透射电镜研究了变温时效对极低碳针状铁索体钢组织和性能的影响规律.结果表明:450-500℃时效处理时,第二相析出较少,组织无明显粗化,强度无明显变化;550-_650℃时效时,强度快速上升,主要是ε-CU和Nb(C,N)第二相粒子的弥散析出所致;650℃以上时效时,发生过时效现象,铁素体板条和第二相粒子粗化,导致强度迅速下降;时效温度达到750℃时进入两相区,局部富C和合金元素富集区域先奥氏体化,时效后冷却过程中形成了高碳的M/A组织,使钢的韧性迅速恶化.     

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。