Mo-Nb单晶材料的加工图及热变形行为（英文）

运用Prasad失稳准则建立了Mo-Nb单晶材料的加工图,研究了材料在1100~1300℃,应变速率0.001~10s~(-1)范围内的热变形特征。结果显示,变形温度和应变速率对Mo-Nb单晶材料的流变应力有着显著的影响。材料的加工图表明,Mo-Nb单晶的最佳热变形条件为变形温度1190℃和应变速率3.16 s~–1。材料的显微组织表明,在1150℃/10s~(-1)和1100℃/0.01 s~-1变形条件下,变形后的样品内部出现了大量的裂纹,且裂纹区域面积较大;经1250℃/0.01 s-1变形的样品,内部只有局部位置出现少量裂纹;1300℃/10s~(-1)变形的样品内部未发现明显的裂纹。X射线衍射结果显示,经1300℃/10s~(-1)变形后的样品仍保持相对较好的单晶组织。表明在1300℃/10s~(-1)变形条件下,样品在变形过程中没有发生变形失稳,这与采用加工图预测的结果相符。     

Mo-Nb单晶的热变形行为及本构方程

采用Gleeble-3800热模拟试验机对Mo-Nb单晶材料的高温流变应力变化规律进行了热模拟实验研究,变形温度区间为1100~1300℃,应变速率为0.001~10 s~(-1),变形程度为50%,真应变量为0.7。结果表明,变形温度和变形速率对Mo-Nb单晶材料的流变应力有较大影响,Mo-Nb单晶材料的真应力-真应变曲线表现出峰值、应变软化和稳态流动等特征。采用修正Arrhenius双曲正弦函数建立了Q、A、n、α等材料常数与真应变的函数关系式,计算了在试验条件下的各种材料参数,推导了Mo-Nb单晶材料高温变形本构方程。     

高强GWZ1042镁合金三维热加工图及可加工性研究

Mg-Gd-Y-Zn-Zr合金是新开发的超高强韧镁合金。在变形温度350～500℃、应变速率0.001～1 s-1的条件下进行了高强度镁合金Mg-10Gd-4Y-1.5Zn-0.5Zr(GWZ1042)的等温热压缩实验,获得了不同变形条件下的应力应变曲线。基于动态材料模型和Murty失稳判据,利用MATLAB软件建立了可描述材料加工性的三维加工图。结果表明,应变速率越小,温度越高,材料的功率耗散系数越大,可加工性越好;温度越低、应变速率和应变量越大,材料越容易发生流动失稳。基于加工图的热加工窗口和失稳区并结合微观组织和缺陷分析确定,GWZ1042合金最佳成形区间为:变形温度430～500℃,应变速率0.001～0.05 s-1。     

Ti-1300合金锻造加工的热压缩模拟

采用Gleeble-1500热模拟机对Ti-1300近β钛合金进行热压缩变形,研究其在温度为800～1010℃、应变速率为0.01～10 s-1、最大变形量为60%条件下的热变形行为.对热变形后的组织进行分析可知,在低应变速率下,主要发生动态再结晶;在高应变速率下,主要发生动态回复.根据试验数据得出了该合金的加工图,结果表明,Ti-1300合金在高应变速率下变形容易发生流变失稳现象,因此其锻造工艺应宜在较低的变形速率下进行,可得较细小的等轴动态再结晶组织.     

Hot Deformation Behavior and Processing Map of SiCp/2024Al Composite

采用Gleeble-1500D热模拟试验机,对30%SiCp/2024A1复合材料在温度为350~500℃、应变速率为0.01~10 s-1条件下进行热压缩试验,研究该复合材料的热变形行为与热加工特征,建立热变形本构方程和加工图。结果表明,30%SiCp/2024A1复合材料的流变应力随温度升高而降低,随应变速率增大而升高,说明该复合材料是一个正应变速率敏感的材料,其热压缩变形时的流变应力可采用Zener-Hollomon参数的双曲正弦形式来描述,在本实验条件下平均热变形激活能Q为153.251 k J/mol。为了证实其潜在的可加工性,对加工图中的稳定区和失稳区进行标识,并通过微观组织得到验证。综合考虑热加工图和显微结构,变形温度为450℃,应变速率为1 s-1是复合材料适宜的热变形条件。     

基于Murty判据的Ti-6.5Al-3.5Mo-1.5Zr-0.3Si钛合金α β相区热变形机制及工艺优化

根据Murty失稳判据,利用原始等轴组织的TC11钛合金在780～990℃和0.001～70s-1范围内的等温恒应变速率压缩实验数据,建立了该合金的加工图.依据加工图研究了TC11钛合金的变形机制和变形缺陷与变形热力参数之间的关系.结果表明,在780～990℃和0.001～0.01 s-1范围是超塑性变形区;在780～990℃和高于0.01 s-1范围,易出现β相裂纹和空洞、局部流动以及绝热剪切等流变失稳现象.根据加工图分析,结合微观组织观察结果,并考虑变形抗力的大小,确定出了较佳的变形热力参数范围为850～940℃和0.001～0.01 s-1,最佳的变形热力参数在900℃和0.001 s-1附近.     

铸态12%Cr马氏体不锈钢的热变形行为与热加工图

利用Gleeble-3180热模拟机对铸态12%wtCr马氏体不锈钢进行了高温热压缩实验,研究了该钢在900~1200℃和0.001~10 s-1条件下的热变形行为,建立了热加工图。分析了工艺参数对铸态12%Cr钢微观组织的影响。结果表明:铸态12%Cr钢的流变应力随变形温度的提高和应变速率的降低而增大。动态再结晶晶粒尺寸与Z参数成反比关系。依据动态材料模型,建立了热加工图,流变失稳区集中在900~1050℃、应变速率大于1 s-1的区域,其微观组织表现为变形带和M/δ相界处的微孔、微裂纹。最佳的热加工工艺参数范围为:1050~1200℃和0.001~0.01 s-1,在稳定变形区,粗大的毫米级的柱状晶会被细化到10~40μm。     

基于BP神经网络和3D加工图的Ti2041合金的热变形行为研究

通过热压缩实验研究了Ti2041合金的流动行为。利用BP神经网络建立的合金本构模型,具有较高的精度,其相关系数达到0.99613,平均相对误差为4.498%,预测值偏差在10%以内的数据点达92.98%。在实验数据的基础上,研究了应变速率敏感因子、功率耗散和失稳参数。建立了加工图,通过加工图的预测和显微组织观察,失稳区主要为局部流动（650~775℃/0.056~1s-1）和机械失稳（825~900℃/0.056~1s-1）,稳定区的变形机制主要为动态再结晶。结果表明：合适的变形参数为：变形温度760~825℃/825~900℃,应变速率0.001~0.01s-1/0.0032~0.056s-1。     

β转变组织TA15钛合金塑性流动失稳行为研究

本文采用THERMECMASTOR-Z型热模拟实验机对魏氏和网篮两种β转变组织TA15钛合金在温度750℃-950℃、应变 速率0.001s-1-10s-1范围进行等温恒应变速率压缩实验。实验结果表明,两种β转变组织钛合金在低温（750℃-880℃）和高应 变速率（0.0032s-1-10s-1）范围存在较大区域的塑性流动失稳,且魏氏组织的塑性流动失稳范围更大,在温度750℃-775℃、应变 速率0.001s-1-0.0032s-1和温度880℃-950℃、应变速率0.56s-1-10s-1区域也出现了塑性流动失稳。魏氏组织的塑性流动失稳缺陷 主要有45°宏观剪切裂纹、微裂纹和局部流动带三种,网篮组织的失稳缺陷主要有45°宏观剪切裂纹和局部流动带两种。魏氏组织比网篮组织更容易发生塑性流动失稳与网篮组织组织更均匀,在变形过程中协调分散性好,不利于产生应力集中有关。     

基于加工图技术的铸态TB6钛合金锻造工艺优化

在Thermecmaster-Z型热模拟实验机上对铸态TB6钛合金在800~1150℃、0.001~10 s-1变形参数范围内进行了等温恒应变速率压缩实验,根据实验数据采用基于Murty准则的加工图技术对该合金的锻造工艺进行了优化,并结合显微组织观察研究了该合金的变形机制。结果表明,在低温区的较佳变形参数为800~950℃、0.001~0.01 s-1,其变形机制为大晶粒超塑性;在高温区的较佳变形参数为1020~1080℃、0.001~0.006 s-1,其变形机制为动态再结晶。失稳区出现在800~890℃、0.01~10 s-1的低温区和975~1120℃、3.162~10 s-1的高温区域,在流变失稳区会出现晶界裂纹。     

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。