30% SiCp/2024复合材料的组织和热处理特性

采用粉末冶金工艺制备了一种SiC颗粒体积分数为30%的SiCp/2024Al复合材料,利用扫描电镜(SEM)、透射电镜(TEM)、能谱(EDS)、电子拉伸和硬度等测试方法研究了不同热处理参数对材料微观组织和力学性能的影响。结果表明:当固溶处理温度达到505℃,可溶相充分回溶,仅剩下含量极少的不可溶相残留在基体中,同时复合材料获得较高的强度;人工时效时间超过100 min后,材料的布氏硬度迅速升高,4.5 h达到峰值,到10 h没有明显的过时效引起的硬度下降。棒针状纳米析出相(S'相)弥散分布于基体中提高复合材料的性能。碳化硅颗粒的加入加速了基体合金的时效动力学,但是基体合金的时效析出过程并没有改变。     

真空热压SiC_p/2024Al复合材料力学性能与显微结构

采用真空热压法制备了体积分数为30%的Si Cp/2024Al复合材料,研究了该复合材料的显微组织结构及力学性能。结果表明,复合材料组织致密,颗粒与基体界面结合状况较好,Si C颗粒在铝基体中基本上分布均匀。经490℃、2 h固溶处理和170℃、8 h人工时效后,Si Cp/2024Al复合材料的抗拉强度、屈服强度和伸长率分别为409 MPa、325 MPa和4.9%,基体中存在大量的纳米析出相为S'(Al2Cu Mg)。随Si C颗粒加入,复合材料力学性能提高,其断裂方式为基体开裂和界面处撕裂。     

热处理对30%SiCp/Al复合材料阻尼性能的影响

采用真空热压烧结法制备30%SiCp/2024Al复合材料以改善2024铝合金的阻尼性能，通过扫描电镜(SEM)、X射线衍射(XRD)、能谱仪(EDS)、高分辨透射电镜(HRTEM)等对复合材料热处理前后的微观组织进行了表征。采用动态热机械分析仪(DMA)研究其热处理前后的阻尼特性。结果表明：热压烧结制备的复合材料界面结合良好，无界面反应，存在许多粗大析出相颗粒，经热处理之后，纳米析出相弥散分布在基体中，可提高复合材料的阻尼性能。30%SiCp/Al复合材料的阻尼性能随温度和应变量的升高而增大，储能模量随温度和应变量的升高而降低。热处理态复合材料中大量弥散的纳米析出相颗粒增加了界面的数量，使界面阻尼增加。复合材料的阻尼机制为位错阻尼、晶界阻尼和界面阻尼。晶界阻尼对温度敏感，大量的界面、晶界可以明显改善复合材料的高温(大于250℃)储能模量，从而改善30%SiCp/Al复合材料的阻尼性能。     

热处理工艺对Al65Cu20Cr15准晶颗粒/Al基复合材料组织与性能的影响

采用热压方法制备了Al65Cu20Cr15准晶颗粒／Al基复合材料，对热处理前后复合材料的显微组织及硬度进行分析，结果表明：在500％高温退火过程中，准晶颗粒中的Cu和Cr原子向纯铝基体中扩散，基体中的Al原子向颗粒中扩散，从而使二十面体准晶相颗粒转变为十次准晶及其类似相，硬度有所降低；基体中，退火过程高温过饱和的Cu以Al2Cu的形式析出，而淬火过程高温过饱和的Cu来不及充分析出，产生固溶强化效应，使淬火后基体的硬度显著增加。     

SiC_p/2024Al复合材料界面的表征及评价（英文）

采用粉末冶金方法制备体积分数为35%的Si Cp/2024 Al复合材料。利用高分辨透射电镜对复合材料中Si Cp与Al基体、析出相与Al基体之间的界面微结构进行表征,采用拉伸弹性模量和布氏硬度测试对界面状况进行评估。结果表明,所得复合材料中Si C与Al的界面整体状况良好。复合材料中SiC/Al界面分为3种类型:大部分干净界面、少量轻微反应型界面以及极少量的非晶层界面。在干净界面中,Si C和Al的结合机制为紧密原子匹配形成的半共格界面,且Si C和Al无固定或择优的取向关系。在轻微反应型界面中,MgA l2O4尖晶石与Si C和Al均形成半共格界面,作为中间媒介很好地连接Si C和Al。复合材料经510°C固溶2 h再在190°C时效9 h后,许多圆盘状纳米析出相和棒针状纳米析出相弥散分布于基体中,且与基体的界面为错配度较小的半共格界面。此时,复合材料的布氏硬度达到峰值。     

热压烧结温度对SiC/Al-Zn-Mg-Cu复合材料微观结构与力学性能的影响

利用粉末冶金法制备了含15%SiC (体积分数)的SiC/Al-7.5Zn-2.8Mg-1.7Cu (质量分数,%)复合材料,采用TEM、EPMA和拉伸实验等分析测试手段,研究了热压烧结温度(500～560℃)对复合材料微观组织和力学性能的影响。结果表明,所选热压温度下均可制备致密无孔洞的复合材料坯锭。热压温度为500和520℃时,SiC/Al界面反应程度较轻,挤压棒材经T6热处理后,Zn元素均匀分布于基体中,但存在的少量富Mg微米级难溶相使复合材料的力学性能产生较大波动。当热压温度升高到540℃时,富Mg难溶相尺寸明显减小,元素分布变得更均匀,复合材料力学性能稳定性明显提升。当热压温度继续升高到560℃时,Mg元素开始向SiC颗粒周围偏聚,界面反应更加严重,而且降低了基体中MgZn_2的体积分数,使复合材料抗拉强度明显下降。对560℃热压的复合材料进行高角度环形暗场像和EDS分析,发现SiC/Al界面同时存在含Mg氧化物和粗大的MgZn_2沉淀相。     

Al-6.4Zn-2.3Mg-2.1Cu超高强铝合金厚板固溶过程的组织演变

采用金相显微分析、扫描电镜和能谱分析等手段,研究了80 mm厚超高强Al-6.4Zn-2.3Mg-2.1Cu铝合金热轧板经第一级470℃以及第二级480℃固溶处理前后的相和组织的演变。结果表明,该合金热轧板中主要存在粗大块状的Al2Cu Mg相、长棒状Al7Cu2Fe相及含Zn Mg Cu的细小析出相等,经470℃固溶处理5 min后,Zn Mg Cu析出相基本溶入基体,90 min后完全溶入基体。经470℃1.5 h+480℃5 h双级固溶处理后存在极少量未溶Al2Cu Mg相,板材组织仍为部分再结晶组织,晶粒总体轮廓与热轧态的相似;随第一级470℃及第二级480℃固溶时间的延长,该合金厚板晶粒形态变化较小,沿轧制方向伸长且部分晶粒中存在细小亚晶组织,亚晶尺寸随固溶时间延长而缓慢长大。     

铸造ZC62镁合金的时效行为

利用光学金相、X射线衍射、扫描电镜和透射电镜研究了ZC62镁合金铸态和固溶时效后的显微组织,初步确定了时效ZC62镁合金中主要合金相的种类和形态,ZC62镁合金铸态组织主要由初晶Mg基体和（Mg＋CuMgZn）共晶构成;固溶处理后,晶界大部分非平衡共晶组织溶解,固溶时效后析出相主要有三类：颗粒相CuMgZn（四方晶系）,尺寸大小约300nm;与颗粒相相连的曲线状“析出相”,长度约1μm;与颗粒相无关的平行、细针状相Mg（Zn,Cu）2（六方晶系）,长约200nm,同时与Mg基面（0001）垂直,并与基体保持某种取向关系．第二类（曲线状）“析出相”实际上是在位错线上形核的Mg（Zn,Cu）2;而第三类（细针状）析出相则是在Mg基体中均匀形核的Mg（Zn,Cu）2。     

固溶处理对消失模铸造B319合金组织及力学性能的影响

研究了固溶处理对消失模铸造B319合金析出相及力学性能的影响。结果表明,在495℃下,随着固溶时间的延长,小部分Al2Cu相会发生相断裂,并溶入Al基体中;固溶温度升高到510℃后,随着固溶时间的增加,Al2Cu相断裂及溶入Al基体中的速度明显加快;495℃或510℃下固溶处理24h,α-Fe、β-Fe相几乎没有变化;但在530℃下固溶处理16h,β相会发生断裂,且数量减少;固溶处理24h后,β-Fe相几乎消失,但α-Fe没有发生明显变化。消失模铸造慢冷条件下,B319合金采用495℃及520℃二步固溶热处理,有利于获得较佳的力学性能。     

激光重熔处理对活塞铝合金组织与性能的影响

运用OM、SEM、EDS、TEM和原位拉伸试验研究了激光重熔处理前后和人工时效处理共晶型活塞铝合金(Al-12Si-2CuNi-Mg)的基体组织、多种复杂析出相的形状和尺寸的演变及其对拉伸强度的影响。结果表明:铝活塞合金重熔前的显微组织由α(Al)、粗大的块状初晶硅、针状共晶硅以及长棒状θ相(Al2Cu)、鱼骨状M相(Mg2Si)、长针状ε相(Al3Ni Cu)、Al7Cu4Ni、Al2Cu Mg和Al9Fe Ni组成;重熔后的显微组织由均匀细小的α(Al)和颗粒状共晶硅组成,复杂的金属间化合物相均已完全溶解,并以固溶原子形式存在于α(Al)里,产生细晶强化和固溶强化作用,使重熔区的拉伸强度提高了31%;经过时效处理,从α(Al)中析出细小均匀的纳米相θ相(Al2Cu Ni)和ε相(Al3Ni Cu),使重熔区的拉伸强度提高了47%。     

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。