Mg-5Zn-3Al-0.2Mn铸造合金的组织和室温力学性能

研究了砂型铸造Mg-5Zn-3Al-0．2Mn合金的显微组织，发现其主要相组成为δ-Mg基体相和τ（Mg12（Al，Zn）49）化合物相，τ相以半连续网状骨骼形态沿δ相的晶界分布。实验合金中加入少量Sr，Ti，B元素后，合金组织细化，τ相形态转变为断续的短条状或粒状，并且分布更加均匀。在本实验条件下，当炉前加入0．06％Ti、0．012％B、0．1％Sr时，合金的组织形态得到显著改善，合金的室温力学性能最佳。不同温度下对Mg-5Zn-3Al-0．2Mn合金进行的固溶处理实验发现，在335℃固溶17h淬火后，合金的室温抗拉强度和塑性得到了大幅度提高；在343℃固溶17h淬火后，合金组织完全转变为单相固溶体，合金的室温力学性能较好，巩为245MPa，δ为12％。     

Mg-xCa-5Zn-3Al-0．2Mn镁合金砂型铸造组织和力学性能研究

研究发现,Mg-5Zn-3Al-0.2Mn合金的砂型铸造组织相组成为δ-Mg基体和τ(Mg32(Al,Zn)49)化合物。在343℃固溶17h后淬火,合金组织完全转变为固溶体,力学性能最佳,σb=245MPa,δ=12%。合金中加入xCa后,组织发生变化。当x=0.43%(质量分数)时,相组成为δ-Mg+Mg-Zn-Al-Ca复杂化合物相。当x=0.95%和1.80%时,相组成为Mg-Zn-Al-Ca相+δ-Mg+Al2Ca。随着x增加,铸态合金室温力学性能呈下降趋势。加Ca合金在350℃固溶17h后淬火,室温力学性能有所提高,而σb250o和σ02.520o则随x增加而稳步提高。     

Sr+Ti+B对ZA53铸造镁合金组织和力学性能的影响

研究了砂型铸造ZA53(Mg-5%Zn-3%Al-0.2%Mn)合金的显微组织后发现,其主要相组成为δ-Mg基体相和τ(Mg32(Al,Zn)49)化合物相,τ相以半连续网状骨骼形态沿δ相的晶界分布。试验合金中加入少量Sr,Ti,B元素后,合金组织细化,τ相形态转变为断续的短条状或粒状,且分布更加均匀。当炉前Ti的加入量为0.06%、B的加入量为0.012%、Sr的加入量为0.1%时,ZA53合金的组织形态得到极大改善,合金铸态室温力学性能最佳。     

固溶时效工艺对ZA27合金组织和性能的影响

采用扫描电镜(SEM)、X射线衍射(XRD)和力学性能测试等手段研究了固溶处理对ZA27合金组织和性能的影响。在300～380℃范围,合金经不同温度固溶处理1 h,水淬后进行相同的时效(160℃×8 h)处理。分析了在不同温度固溶处理的淬火态和时效态合金的显微组织及力学性能。结果表明,在365℃固溶处理能够使溶质原子充分溶入基体,时效析出相数量多、尺寸小、分布均匀,时效强化效果最好。ZA27合金的优选固溶工艺为365℃×1 h。     

固溶处理对ZA35-0.1Ti合金组织和力学性能的影响

利用X射线衍射和金相显微镜等手段研究了不同固溶时间下ZA35-01Ti合金的组织,并测定合金的力学性能,观察了合金的断口形貌,研究固溶处理对ZA35-01Ti合金组织和力学性能的影响.结果表明:ZA35-0.1Ti合金在385℃下随固溶时间延长力学性能先提高后下降,在固溶时间为5h时,合金抗拉强度为396.0MPa,伸长率为3.71％,布氏硬度为140HBS,力学性能达到最优;合金经385℃×5h固溶处理后,合金元素Ti全部固溶于合金中,固溶强化效果显著.     

Y、Gd对ZA63镁合金组织和力学性能的影响

通过合金制备、微观分析和力学性能测试等方法研究了Y、Gd复合稀土对ZA63镁合金组织和力学性能的影响。结果表明,添加适量RE元素后,ZA63合金中的τ相由半连续网状分布转变为针状或棒状且分布较均匀,ε相由岛状变为细小颗粒状,部分RE元素固溶于τ相中形成Mg-Al-Zn-RE相。随着RE含量的增加,经T6处理后的合金在室温、150℃和175℃下的抗拉强度和伸长率基本都呈先升高后降低的趋势。当RE含量为1.5%时,合金在3个温度下的抗拉强度和伸长率都达到最大值。     

热处理对M963合金显微组织和拉伸性能的影响

研究了不同热处理工艺对M963合金显微组织和拉伸性能的影响。结果表明，经1210℃，4h空冷固溶处理后，合金的强度升高，但塑性降低，尤其是在高温(900℃)时塑性降低幅度更大：固溶处理后再进行850℃，16h炉冷时效，强度进一步提高，高温塑性获得恢复，但室温塑性进一步降低。扫描电镜观察发现：合金在l210℃，4h空冷固溶处理过程中，初生MC碳化物发生转变，并在晶界和枝晶间析出M6C碳化物；在固溶处理后的空冷过程中，从γ溶体基体中析出细小γ相；经850℃，16h低温时效后，γ充分析出并长大。断口形貌分析表明不同热处理状态的合金，其断裂机制不同。根据位错与强化相之间的相互作用理论讨论了这种热处理工艺对室温和高温拉伸性能的不同影响规律。     

均匀化对7050铝合金板材淬火敏感性的影响

通过光学显微镜、透射电镜以及力学性能测试,研究均匀化制度对7050铝合金板材组织演变的影响。将合金固溶后在不同速率淬火,研究均匀化制度对该合金淬火敏感性的影响。结果表明:固溶后慢速率淬火过程中,平衡相η主要位于再结晶晶粒中Al3Zr粒子的相界、再结晶晶界、亚晶晶界以及亚晶中与位错交互作用的少量Al3Zr粒子上形核析出;均匀化时间较短时(室温,120℃/h升温至465℃,8h),合金中析出少量Al3Zr粒子,固溶后的试样发生完全再结晶,此时合金淬火敏感性最好,但硬度较低;延长保温时间至20h(室温,120℃/h升温至465℃,20h),试样中析出大量Al3Zr粒子,但分布不均匀,从而导致轧制固溶后的试样依然明显再结晶,合金淬火敏感性较差;采用快速升温的双级均匀化制度((室温,120℃/h升温至465℃,20h)+(475℃,8h)),Al3Zr粒子有所长大,淬火敏感性最差;采用慢速随炉升温((室温,18℃/h升温至465℃)+(475℃,8h))的双级均匀化制度,合金中将弥散析出大量细小的Al3Zr粒子,固溶后的再结晶得到有效抑制,较多η相在亚晶界上的非均匀形核析出在一定程度上增加了合金的淬火敏感性,但该制度处理的合金仍优于再结晶程度较高的快速升温双级均匀化制度的。     

90 ℃时效对固溶态ZA27合金组织与性能的影响

对ZA27合金进行365℃/3 h的固溶化处理,研究90℃时效对其拉伸性能及阻尼性能的影响。结果表明,固溶态ZA27合金经过90℃、6 h时效后的组织主要由α相和η相层片组织组成,另有少量粒状组织。固溶态合金的拉伸强度和阻尼性能均较低,伸长率较高。时效使合金拉伸强度和阻尼性能先提高后下降;使延伸率先降低后提高。时效6 h后ZA27合金的拉伸强度为401 MPa,伸长率为6.6%,阻尼性能为3.0×10^-3。     

Ti-38644合金中硅化物的溶解析出及对力学性能的影响

研究了Ti-38644合金中硅化物的溶解和析出行为及其对室温拉伸性能的影响,并利用扫描电镜和透射电镜对显微组织、析出相及拉伸断口进行了观察和分析。结果表明,合金中的杂质Si导致(TiZr)_6Si_3硅化物的形成。在700~950℃之间固溶1 h后,合金中的硅化物随固溶温度升高逐渐溶解,而950℃固溶样品中未观察到硅化物。由于硅化物的溶解和β晶粒长大,800~950℃之间固溶后的合金强度随固溶温度升高而降低。合金经1100℃固溶1 h,再经750~900℃时效1 h后,硅化物在晶界处析出,而在700℃和950℃时效1 h的样品中未见硅化物的析出。800~950℃之间时效后的合金强度基本不变,晶界硅化物对合金抗拉强度影响不大,但合金塑性随晶界硅化物含量减少而提高,断裂模式由脆性断裂转变为韧性断裂。     

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。