热处理对7B04铝合金厚板组织与力学性能的影响

通过显微组织观察和力学性能与电导率测试,研究了热处理工艺对7B04铝合金厚板组织与性能的影响。结果表明,适宜的固溶工艺为470℃×240min。120℃×22h时效后合金可获得,抗拉强度为621MPa,但合金的电导率较低,仅为18·3MS/m;双级T74时效时,强度下降了10%～12%(与T6态相比),电导率获得了明显提高,为21·3MS/m;三级时效(RRA)处理可使合金获得高强度和高电导率相结合,强度接近T6态,电导率与T74态相当。合金经RRA处理后,基体内分布着大量的细小弥散析出相(与T6态组织相似),晶界析出相粗大且呈完全不连续分布。     

新型高强韧低淬火敏感性Al-7.5Zn-1.65Mg-1.4Cu-0.12Zr合金

利用传统技术制备新型高强韧低淬火敏感性的Al-7.5Zn-1.65Mg-1.4Cu-0.12Zr合金,研究合金在制备加工以及不同热处理状态下的微观组织和性能.结果表明:该新型合金铸态组织具有枝晶间非平衡共晶相AlZnMgCu相对较少的特点,经过(440 ℃, 12 h)+(475 ℃, 24 h)双级均匀化处理、挤压变形和(475 ℃, 50～120 min)固溶处理后,组织均匀,固溶充分,除弥散分布的Al3Zr粒子外,仅残留有少量的Al7Cu2Fe相颗粒;经过单级、双级和三级时效处理,合金可以获得比较理想的组织和性能:T6态合金的抗拉强度590 MPa,电导率20.4 MS/m;经T7双级时效处理后,合金的抗拉强度、屈服强度、断后伸长率和电导率分别达到500～550 MPa、460～520 MPa、 17.0%～17.3%和23.4～25.0 MS/m;经三级时效处理后,合金的组织和力学性能兼顾了T6和T7两种制度的优势,与T6状态相比,在抗拉强度仅降低3%的情况下,电导率显著增加至23.1 MS/m;合金具有低的淬火敏感性,室温水端淬试验测得的淬透深度可以达到120 mm以上;新型合金具有优异的室温断裂韧性,其T6态的KIC值明显高于本研究同时制备的7150合金.     

时效态Cu-Fe-P合金组织和性能的研究

利用微合金化法设计了引线框架用Cu-Fe-P合金的成分(Cu-2.5Fe-0.12Zn-0.03P-0.05Mg-0.05Cr-0.05RE),采用金相显微镜(OM)和高分辨电子显微镜(HRTEM)研究了合金的微观组织,测定了合金的抗拉强度、伸长率及电导率等性能.试验结果表明,在其他试验条件相同的情况下,冷轧后的合金板材经550 ℃×4 h时效后处于过时效状态,球形的析出相γ-Fe粗化,尺寸在50～100 nm的范围,合金的强度为482 MPa,显微硬度HV为161,电导率为39.7 MS/m;经450 ℃×4 h时效后处于欠时效状态,呈球形的γ-Fe相尺寸在20 nm以下,抗拉强度为417 MPa,显微硬度HV为139,电导率是30.4 MS/m;经550 ℃×2 h 450 ℃×2 h时效后处于峰值时效状态,球形的γ-Fe相尺寸在20～50 nm的范围,此时合金的抗拉强度为510 MPa,显微硬度HV为168,导电率为40.6 MS/m.     

新型7056铝合金双级时效的显微组织和性能

采用力学性能和电导率测试以及透射电子显微镜组织等观察分析新型7056铝合金双级时效制度下的性能和显微组织。结果表明:第二级时效处理后,合金基体沉淀析出相长大粗化,晶界析出相逐渐呈断续分布状态,无析出带随时间的延长而变宽;经第二级150℃、12 h时效后,合金由GP区和η相构成,析出相的尺寸为7~9 nm,并出现明显的无析出带;随着第二级时效时间的延长,合金电导率逐渐升高,屈服强度先增大后减小;合金经(110℃、6 h)+(150℃、14 h)双级时效处理后,屈服强度达到650 MPa,电导率为21.72 MS/m,表现出优异的综合性能。     

回归再时效处理对7050铝合金微观组织与性能的影响

采用拉伸试验、电导率测试和透射电镜分析等方法研究了7050厚板在185℃回归再时效过程中的析出行为,并与T6时效工艺进行了比较研究。结果表明,7050-T6的合金强度较高(屈服强度约为507 MPa),但其耐应力腐蚀性能较差,电导率仅为16.59 MS/m。经回归处理后,合金的力学性能呈上升后下降的趋势,电导率呈现总体上升的趋势。当回归处理1h时,7050-RRA合金的屈服强度提升至523 MPa,电导率达到20.07 MS/m,综合性能优异。TEM结果表明,T6处理后,基体强化相主要为GP(I)区和η′相;随着回归时效进行,GP(Ⅰ)区开始转变为GP(Ⅱ)区和η′相,η′相逐渐增多使强度上升至峰值;回归处理4h后,GP区基本消失,η′相开始转变成η相,合金强度下降。     

固溶-时效对01975Al-Zn-Mg-Sc合金板材组织性能的影响

采用拉伸力学性能、硬度、电导率测试、金相和电子显微分析技术,研究了固溶-时效处理对01975Al-Zn-Mg-Sc合金板材组织与性能的影响。结果表明:01975铝合金板材最佳固溶时效制度为470℃1 h固溶+120℃24 h时效。在此条件下,合金的抗拉强度、屈服强度、伸长率、硬度和电导率分别为532 N/mm2、496 N/mm2、15.07%、176.1HB和34.3%(IACS)。合金的高强度来源于Al3(Sc,Zr)粒子引起的亚晶强化和η'相引起析出强化。     

7055铝合金的非等温双级时效行为

采用硬度测试、电导率测试、室温拉伸实验、剥落腐蚀实验、DSC分析以及TEM观察,研究了非等温双级时效对7055铝合金组织及性能的影响。结果表明:在第二级时效的连续升温阶段,晶内由GP区、η′和α-Al三相共存状态逐渐演变为η′、η和α-Al三相共存态。在第二级时效的连续降温阶段,晶内二次析出GP区和η′相,合金硬度再次升高。晶界η相在时效过程中不断粗化并呈断续分布,合金电导率持续增加。非等温双级时效的第二级升温速率和最高时效温度(T_p)决定了合金的性能。在相同性能水平下,快速升温对应相对更高的T_p。以电导率22 MS/m为标准,1℃/min升温速率对应的T_p为215℃,而3℃/min升温速率下T_p则为225℃。经过105℃、24 h预时效并包含升降温的非等温二级时效,7055铝合金的抗拉强度和剥落腐蚀等级可达610MPa和EB级别,表现出比T6和T73态更加优异的综合性能,且取消等温保温阶段实现了热处理工艺的短流程操作。     

快速凝固Cu-Cr-Sa-Zn合金的时效强化研究

研究了时效温度、时效时间对快速凝固Cu-Cr-Sn-Zn合金微观组织、显微硬度和电导率的影响规律.结果表明,快速凝固状态下合金细晶强化作用显著,硬度(HV)和电导率分别为100和20.9 MS/m.合金快速凝固时效后的析出相Cr弥散、稠密,使合金强度和电导率得以提高,在500℃×15 min时效后,硬度(HV)为170,电导率达37.1 MS/m.     

新型Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr合金单级时效行为研究

通过力学性能和电导率测试以及显微组织的TEM分析,研究新型Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr合金的单级时效行为特征.结果表明:当时效温度由100 ℃升高至160 ℃时,合金时效硬化响应速度明显加快,合金进入过时效状态所需的时间缩短,合金的电导率明显提高.与通常的120 ℃,24 h峰时效态相比,合金经140 ℃, 14 h时效处理后,抗拉强度、屈服强度、断后伸长率和电导率分别达到585 MPa, 560 MPa, 16.1 %和22.6 MS/m,其抗拉强度仅降低1%,屈服强度却提高4%,电导率更是提高11%,作为单级时效制度具有较明显的优势.合金峰时效状态下的主要强化相是细小弥散分布的η'相和GP区.随着时效温度的升高,晶内和晶界的析出相粗化,140 ℃时效时出现明显的晶间无析出带.     

喷射沉积Al-Zn-Mg-Cu合金的组织及力学性能研究

利用喷射成形技术制备了高Zn含量的Al-Zn-Mg-Cu铝合金,合金经挤压后,对其进行固溶时效处理并进行力学性能测试,合金的抗拉强度为849 MPa,屈服强度为796 MPa,延伸率为3.3%;利用TEM、SEM对拉断后的试样进行显微组织结构与断口形貌的观察和分析发现合金组织为细小的等轴晶,大小为2～3 μm,沉淀析出相为GP(Ⅱ)区及少量的η'相、η相;Zn元素的偏聚析出,引起明显的晶格畸变;断口形貌主要为沿晶断裂.     

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。