时效温度对Zn-4Al-2Cu-0.5Mg-0.1Y锌合金组织和性能的影响

采用金属型铸造法制备了Zn-4Al-2Cu-0.5Mg-0.1Y锌合金。采用光学显微镜、扫描电镜、X射线衍射仪和显微硬度仪等研究了时效温度对其微观组织、力学性能和导电率的影响。结果表明:铸态锌合金组织主要由η(Zn)固溶体和共晶体结构η(Zn)+α(Al)组成;时效温度为140℃时,锌合金的拉伸强度达到最大,为263 MPa,时效温度为160℃时,其导电率最高,为23.28%IACS,时效温度在180℃时,其硬度最大,为148.7 HV。锌合金的磨损机制为塑性变形和粘着磨损的混合,拉伸断裂机制为解离断裂。     

高强耐蚀Ni-Co-Cr高温合金的组织稳定性

利用SEM，TEM及X射线衍射分析技术观察了高强耐蚀Ni-Co-Cr高温合金不同温度（704，750，849℃）长期时效1000h及700℃长期时效至5008h过程中的组织演变过程。结果表明，700℃即使长期时效5008h，γ‘相粗化缓慢，而且没有发现TCP相（如σ相）的析出。当温度升高到750℃，γ‘相迅速长大。晶界上碳化物析出增多，并析出片状的η相。导致合金冲击性能下降。温度达到849℃时，析出大量的η时。甚至形成魏氏组织形貌。由此可见，该合金在700℃时具有较好的组织稳定性。     

热处理工艺对锌合金组织和力学性能的影响

通过力学性能测试、扫描电镜等试验,研究锌合金经过热处理后的组织和性能。结果表明:热处理后锌合金晶粒细化,由等轴状的η(Zn)相、共晶组织以及第二相组成;200~350℃热处理3 h随炉冷却使共晶组织由片层状转变为颗粒状;较好的热处理工艺是350℃保温3 h,随炉冷却,锌合金的抗拉强度达到190 MPa,伸长率达到10%。     

新型高强2A97铝锂合金组织和性能研究

通过室温拉伸、布氏硬度试验和TEM、XRD等手段,研究了新型高强Al-Li-Cu-X合金2A97在淬火变形4%后135℃时效组织和性能的演变。结果表明：2A97合金经淬火变形后在135℃时效,随时效时间增加,抗拉强度和屈服强度先升高后降低,塑性逐渐下降,峰值时效135℃,48h的抗拉强度为577MPa,屈服强度为519MPa,伸长率为6.7%,布氏硬度值先快速升高后缓慢增加。淬火变形后时效的显微组织主要为T1（Al2CuLi）、θ′/θ″（Al2Cu）、δ′（Al3Li）和δ′/β′（Al3Zr）共生相,随时效时间增加,T1相数量和尺寸增加,δ′相数量增加,直径减小。     

高强Al-Cu-Li-X铝锂合金形变热处理

采用拉伸试验、透射电镜和扫描电镜等手段,研究了淬火后形变时效对新型高强Al-Cu—Li—X铝锂合金2A97组织和性能的影响。结果表明：淬火后立即预变形引入的位错和随后双级时效过程形成的位错环增加基体T1相和θ’相数量,并使T1相细化,分布更均匀。双级时效合金θ’相、δ’相和T1相组成的混合组织强度低于单级时效以T1相为主强化的组织,但塑性高于单级时效。淬火变形后双级时效100℃,8h＋145℃,12h处理合金的抗拉强度、屈服强度和伸长率分别为553．5MPa,494．5MPa和10．4％,形变时效处理在一定程度上改善了合金的强塑性匹配。     

喷射成形Al10.8Zn2.8Mg1.8Cu合金沉淀析出强化行为

采用喷射成形技术制备Al10.8Zn2.8Mg1.8Cu高强铝合金,利用力学性能测试、高分辨透射电镜(HREM)、选区衍射(SAED)等手段系统研究120℃下该合金的时效曲线和沉淀析出行为。研究结果表明:该合金在120℃时效4h强度即可达到800MPa以上;16h达到峰时效状态,强度可达820MPa,此阶段GPⅠ区和GPⅡ区联合强化起主导作用;44h后存在长时间的时效平台,强度在800MPa左右,此阶段η′相和η相起主导强化作用。     

预热变形对A286高温合金时效后组织和硬度的影响

对固溶后A286合金进行不同温度的热变形,并时效处理,研究不同热变形温度对合金后期时效硬度的影响。采用光学显微镜、扫描电镜、能谱仪、X射线衍射、背散射电子衍射和硬度计等仪器,分析了不同状态下合金的形貌、成分、相组成、形变特点和硬度。结果表明,A286合金时效后的外边缘析出有大量η相,其来源于热变形过程的热变形和后期时效处理的综合作用,热变形过程使合金产生层错堆叠,为η相析出的可能性提供能量基础,时效过程则提供η相析出所需原子扩散的温度环境。随着热变形温度的升高,合金再结晶程度明显,有利于之后进行时效处理时强化相的均匀细小析出和组织优化,η相的析出量减少,合金硬度升高。     

含Sc超高强Al-Zn-Mg-Cu-Zr合金的回归再时效处理制度

采用透射电镜分析、力学拉伸性能测试和电导率测试, 研究不同回归再时效(RRA)处理制度对含Sc超高强Al-Zn-Mg-Cu-Zr合金组织与性能的影响.结果表明:采用120 ℃,24 h预时效+180 ℃,30 min回归处理+120 ℃,24 h终时效的RRA处理工艺,可以使合金获得理想的力学性能和抗应力腐蚀性能;与T6态相比,该工艺获得的合金强度仅略微下降,而电导率则大大提高;含Sc超高强Al-Zn-Mg-Cu-Zr合金经RRA处理后,晶内含大量均匀细小的η'相和少量的η平衡相,合金晶界处的平衡相粗化明显,呈现断续、孤立分布;与T6态处理的合金相比,无沉淀析出带变宽;其晶内析出相与T6峰值时效态的类似,晶界组织与双级过时效态的组织类似.     

时效温度对Zn-1.5Cu-1.2Mg-0.2Zr合金组织与耐蚀性的影响

采用金属型铸造的方法制备了Zn-1.5Cu-1.2Mg-0.2Zr锌合金，利用扫描电镜、能谱仪、X射线衍射、电化学工作站和浸泡实验等研究了不同温度时效处理对其微观组织和耐蚀性的影响。结果表明：铸态锌合金的微观组织主要由η相(含Cu的Zn固溶体)、η+Mg₂Zn₁₁共晶体和少量的Zn-Zr化合物组成；随时效温度的升高，合金η相晶粒内析出的片状第二相数量先增加后减少，腐蚀速率呈先降低后增加的趋势；220℃时效处理的锌合金腐蚀速率最小，自腐蚀电流密度和模拟体液浸泡腐蚀速率分别为5.23μA·cm^-2和0.053 mm·year^-1,这可能是由于220℃时效处理后合金η相晶粒内析出的片状第二相的数量最多且分布均匀。     

双级时效对AA7050合金组织和性能的影响

研究了双级时效的预时效阶段及高温短时回归时效处理对AA7050合金组织和性能的影响。结果表明,AA7050合金时效硬化效果明显,预时效温度越高,硬化速率越快;在不高于135℃下时效,具有较好的抗过时效能力。135℃下预时效12 h后,晶内组织以GP区为主,且晶界平衡相细小连续,无明显晶界无析出带,合金强度处于亚峰值状态。170℃高温二级时效处理时,随时效时间延长,合金强度先上升后下降;时效2 h时,综合力学性能最佳,晶内主要强化相为GP区和η’相,晶界为不连续的η相,伴随10～20 nm的晶界无析出带,随二级时效时间延长,晶内η’相大量向η相转化,强度迅速下降。     

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。