铁素体含量对309L焊条焊后热处理态拉伸性能影响研究

选用2个批次不同铁素体含量的309L焊条,在不同模拟焊后消应力热处理(SPWHT)保温时间状态下进行熔敷金属拉伸试验。试验结果表明,随着SPWHT保温时间的延长,高铁素体含量焊条的断后伸长率显著下降,低铁素体含量焊条的熔敷金属始终保持较好的塑性。通过试样断口分析、金相组织观察和扫描电镜观察,韧性δ-Fe在SPWHT过程中转变为脆性σ相,是造成高铁素体含量的309L焊条断后伸长率显著下降的主要原因。本研究为新型核电工程用不锈钢堆焊材料的设计、采购和验收提供了重要依据。     

核电用EQ309L不锈钢带极埋弧堆焊材料的研制

通过合理调整EQ309L熔敷金属的铁素体含量,提高了长时间热处理后熔敷金属的断后伸长率;对EQ309L焊带进行控氮处理,解决了室温抗拉强度不能稳定大于等于520 MPa的难题;通过改变焊剂中碳酸盐、硅酸盐及氟化物的比例改善焊剂工艺性能,解决了表面压痕和粘渣问题.研制出的EQ309L不锈钢带极埋弧堆焊材料WEQ309HR...     

FM-52M镍基合金堆焊层高温拉伸性能研究

在304不锈钢钢板采用TIG堆焊了FM-52M镍基合金,并利用Gleeble热模拟试验机对FM-52M堆焊层试样在不同条件下的高温拉伸性能进行了研究。结果表明:经750℃保温30 min处理后,FM-52M合金的强度与750℃保温30 s处理的相比明显降低;在高温、应力缓慢加载的条件下,FM-52M的力学性能明显下降。热处理温度为950℃时,拉伸速率为0.01 mm/s的堆焊试样强度和断后伸长率均比拉伸速率为0.5 mm/s的小。经过1200℃的峰值温度保温后,合金的屈服强度比950℃的试样略低,但断后伸长率更好。     

核级E309L-16奥氏体不锈钢焊条的研制

核岛主设备核心部件使用的E309L-16奥氏体不锈钢焊条长期依赖进口,严重制约中国核电事业的发展.研究了焊态铁素体含量对熔敷金属经608℃×40 h热处理后断后伸长率的影响,对焊态铁素体含量大于12％的热处理态熔敷金属微观组织进行分析,并研究了热输入和热处理保温时间对熔敷金属拉伸性能的影响,试验结果表明:当铁素体含量大...     

焊后热处理对双相钢焊条电弧堆焊层组织性能的影响

双相不锈钢在室温下固溶体中奥氏体和铁素体约各占一半且兼有两相组织特征.它保留了铁素体不锈钢强度高、导热系数大、线膨胀系数小、耐点蚀,缝蚀及氯化物应力腐蚀性能的特点;又具备奥氏体钢不锈钢韧性好、脆性转变温度较低、抗晶间腐蚀、力学性能和焊接性能好的优点.通过对2209型双相钢焊条电弧堆焊层的在焊态及焊后经过690℃下不同时间的热处理态后堆焊层的组织和性能进行了试验.试验结果表明,经焊后热处理的堆焊层,铁素体含量降低、力学性能下降、硬度增高、腐蚀性能下降,这主要是由于堆焊层经热处理后,未能保持适当的相比例和σ相的析出,导致堆焊层的力学性能和耐蚀性能下降.     

热处理工艺对M390/304 CMT焊接接头微观组织及力学性能的影响

基于改善M390高碳马氏体不锈钢与304奥氏体不锈钢焊接接头的力学性能特别是提高焊接接头硬度,以达到高端刀具生产的要求,对冷金属过渡焊接M390高碳马氏体不锈钢与304奥氏体不锈钢获得的焊接接头进行不同工艺的热处理研究.采用拉伸、维氏显微硬度测试及扫描电镜(SEM)表征不同热处理工艺的焊接接头力学性能及微观组织演变,统计了不同热处理工艺下焊接接头中M390母材、M390细晶区和M390粗晶区等区域的碳化物分布,研究了不同热处理工艺下焊接接头的断裂机理.研究结果表明,在1 150℃水淬热处理工艺下焊接接头既满足刀具钢硬度的要求,又具有良好的力学性能,可以作为M390/304焊接接头的最佳热处理工艺,对应焊接接头的抗拉强度和断后伸长率为502 MPa和20.8%,抗拉强度和断后伸长率分别是焊态的98%和95%. 1 150℃水淬热处理工艺的M390母材、细晶区和粗晶区中碳化物平均尺寸最小,碳化物形貌以细小的块状均匀分布.淬火温度升高,抗拉强度和断后伸长率均呈现出先下降后升高的趋势,随着冷却速度的减小,抗拉强度和断后伸长率均呈现出下降的趋势.不同热处理工艺下焊接接头的断裂位置在M390粗晶区...     

带极埋弧堆焊EQ309L的焊接工艺和接头性能

为了研究堆焊单一E309L熔敷金属的焊接工艺和接头性能,采用埋弧焊(SAW)在14Cr1MoR基体上堆焊一层EQ309L焊带,焊接过程中严格控制焊接热输入和采用有效的消应力退火热处理制度,保证堆焊层顺利通过无损检测以及弯曲、化学、铁素体数量、硬度试验、金相组织分析和晶间腐蚀等理化性能检测。结果表明,采用埋弧焊(SAW)堆焊单层EQ309L时堆焊层的塑韧性能满足要求,晶间腐蚀试验合格,可以用在压力容器的表面堆焊中。     

热处理对添加稀土元素的AZ51镁合金组织及性能的影响

研究了热处理对添加稀土元素的AZ51镁合金强度及塑性的影响。结果表明:AZ51新型镁合金抗拉强度为315.6 MPa,断后伸长率达到23%,硬度为61.7 HV;经过T5处理后,晶粒细化,抗拉强度提高1.6%,断后伸长率下降7%,硬度提高29%;经过T6处理后,抗拉强度下降2.5%,断后伸长率下降20%,硬度下降6%。添加微量稀土元素的AZ51新型镁合金韧塑性有明显的提高,T5时效热处理后,镁合金的性能有所提高,但不明显;T6热处理后,镁合金的性能有所下降。     

W对Fe-Cr-Mo-W-V热锻模具堆焊合金组织与性能的影响

针对热锻模具工作条件及其失效形式,采用药芯焊丝气体保护堆焊方法制备Fe-Cr-Mo-W-V系热锻模具堆焊合金,采用金相组织观察、硬度测试、回火热处理、抗热疲劳裂纹和力学性能等多种试验方法,分析了W含量对堆焊合金显微组织、焊态硬度、热稳定性、热疲劳性能以及力学性能的影响。结果表明:Fe-Cr-Mo-W-V系堆焊合金的显微组织由板条马氏体+残余奥氏体组成。随着W含量的增加,堆焊合金焊态及550℃回火处理后所对应的硬度值逐渐增加,随着热处理时间的延长,堆焊层硬度逐步降低并趋于平缓。随着堆焊合金中W元素的增加,堆焊合金抗热疲劳裂纹性能逐渐降低,Fe-Cr-Mo-W-V系堆焊合金的抗拉强度略高于国外焊接材料Weld Mold 9650,断后伸长率略低于焊接材料Weld Mold 9650。     

核电安全端Inconel 690合金堆焊层界面微观组织及力学性能研究

Inconel690镍基合金因其优异的抗晶间腐蚀能力而常应用于压水堆核电蒸汽发生器的管板堆焊隔离层。采用热丝TIG堆焊的方法在核电用SA508Gr.3Cl.2低合金钢表面堆焊Inconel 690镍基合金隔离层,并在焊后进行等温热处理以消除残余应力。采用OM、SEM、XRD对堆焊层和基体金属进行了组织表征,并对堆焊层和母材进行冲击韧性、硬度及拉伸性能进行测试和分析。研究结果表明,堆焊层组织在室温下的抗拉强度达到541.4 MPa,断后伸长率达到39.89%,基体低碳钢的抗拉强度为687.3 MPa,伸长率为20.8%。通过显微硬度测试得出堆焊层奥氏体组织平均硬度为140.8 HV,低于母材的159.5 HV。Inconel690堆焊层晶界附近析出的M_(23)C_6、NbC以及Ti C等碳化物相可对晶界产生钉扎作用,其在界面上的分布状态对提升堆焊层的高温力学性能和服役安全具有重要意义。     

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.     

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.