激光沉积修复GH738合金时效热处理组织及性能

研究了双极时效热处理对激光沉积修复GH738合金显微组织及力学性能的影响。结果显示:沉积态显微组织为典型的外延柱状枝晶,枝晶间距约为10μm。经过时效处理后,修复区组织开始长大、合并。沉积态未发现γ′相,枝晶间存在立方状的MC型碳化物,枝晶干存在颗粒状M_23C_6型碳化物。经双级时效处理后,修复区析出γ′相:稳定化温度为820℃时,γ′相平均尺寸约为37 nm,碳化物在晶界处呈断续状析出。随着稳定化温度升高,γ′相及碳化物尺寸均有所增大,其中稳定化温度为840℃时,γ′相平均尺寸约为76 nm,碳化物呈项链状析出;稳定化温度为860℃时,γ′相平均尺寸无明显增大,部分γ′相发生明显粗化,尺寸达到150 nm,晶界处碳化物开始呈包膜状析出。力学性能测试结果显示:时效处理后试样抗拉强度明显提高,随着稳定化温度升高,抗拉强度先升高后降低,断后伸长率不断降低。     

激光增材制造DD98M高温合金组织及稳定性研究

采用激光增材制造技术制备了DD98M镍基高温合金管状试样,研究了其沉积态、固溶时效态和长期时效态微观组织变化,对比分析了沉积态和固溶时效态试样中γ'相尺寸分布及在1000℃长期时效时γ'相的演化规律。结果表明:沉积态组织主要由外延生长的微细柱晶组成,枝晶间无γ-γ'共晶组织析出,试样中γ'相体积分数约为70%。合金中元素微偏析造成了枝晶干和枝晶间γ'相尺寸差异,其中枝晶干处为210 nm,枝晶间为560 nm。经固溶时效处理后,γ'相(约370 nm)均匀分布在γ基体上,其尺寸分布符合LSW模型。经1000℃长期时效500 h后,合金组织中无TCP相(拓扑密排相)生成,γ'相仍保持立方形貌,其尺寸几乎保持不变。固溶时效处理后,合金显微硬度从沉积态时的4420 MPa增加至4870 MPa,长期时效能降低合金硬度,降幅约5.9%。     

热处理对一种新型增材制造镍基高温合金显微组织与拉伸性能的影响

本文研究了不同热处理工艺对一种新型增材制造镍基高温合金ZGH451组织性能的影响。结果表明,沉积态组织主要由外延生长的微细柱晶组成,枝晶间存在γ/γ＇共晶组织,合金中元素偏析造成了枝晶干与枝晶间处γ＇相尺寸差异,分别为100 nm和250 nm。不同热处理工艺合金的组织和性能存在一定差异：随着固溶温度由1180 ℃升高到1350 ℃,合金偏析程度逐渐减弱,直至1350 ℃发现初熔组织;随着一级时效温度由1050 ℃升高到1150 ℃,γ＇相的尺寸逐渐增大,形状由球状等不规则形状转变为立方状。综上,优化出适用于该合金的热处理工艺（HT2）,与沉积态合金相比,完全热处理后合金的晶粒尺寸明显增大,且消除了合金的偏析及γ/γ＇共晶,在1000 ℃拉伸变形过程中γ/γ＇界面形成致密的位错网,抗拉强度和屈服强度分别为520 MPa和269 MPa,延伸率为11%。     

激光成形修复Inconel 625合金的工艺特性和组织研究

对激光成形修复Inconel 625合金的工艺特性以及不同区域的组织进行了研究。结果表明:激光成形修复Inconed625合金的工艺范围较宽;激光功率主要影响单道修复层的宽度;扫描速度对单道修复层的尺寸影响较为显著,而送粉率的影响较小。基材的相组成包括γ(Ni-Cr)基体相、大尺寸(约10μm)块状MC型碳化物(M为Nb和Ti)、沿晶界析出的小尺寸(约0.5μm)块状MC型碳化物以及不规则形状的Laves相。修复区组织为呈外延生长的柱状枝晶,相组成为γ基体相、沿枝晶界析出的Laves相以及少量MC型碳化物。层与层界面处Laves相析出急剧增加形成层间过渡区。     

激光沉积修复DZ125合金的组织与摩擦磨损性能

在DZ125高温合金铸造基体上进行激光沉积修复实验,研究了激光沉积修复显微组织、硬度及摩擦磨损性能。结果表明:沉积区底部为宽度约8μm的平面晶、沿沉积高度方向外延生长排列紧密的柱状晶,中部为树枝晶,顶部为杂乱无章的等轴晶;沉积区层与层交界处γ'相尺寸大于层内,晶界处γ'相尺寸大于晶内;γ+γ'共晶相和MC碳化物明显沿晶界分布,沉积区中下部多为短棒状MC碳化物,沉积区顶部多现小块状以及八面体状MC碳化物。基体HV_(0.3)显微硬度为4.1～4.2 GPa,沉积区显微硬度高于基体,为4.55～4.75 GPa。沉积区磨损机理主要是轻微的磨粒磨损,耐磨性能优于基体。     

激光沉积修复DZ125组织与摩擦磨损性能

在DZ125铸造基体上进行激光沉积修复实验，研究了激光沉积修复显微组织、硬度及摩擦磨损性能。结果表明：沉积区底部为宽度约8μm的平面晶、沿沉积高度方向外延生长排列紧密的柱状晶、中部为树枝晶、顶部为杂乱无章的等轴晶；沉积区层与层交界处γ"相尺寸大于层内，晶界处γ"相尺寸大于晶内；γ+γ"共晶相和MC碳化物沿晶界分布现象明显，沉积区中下部多为短棒状MC碳化物，沉积区顶部多现小块状以及八面体状MC碳化物。基体显微硬度为410～420HV0.3，沉积区显微硬度高于基体，为455～475 HV0.3。沉积区磨损机理主要是轻微的磨粒磨损，耐磨性能优于基体。     

热处理对SLM成形的Inconel 718合金组织的影响

研究了固溶+双级时效处理对激光选区熔化(SLM)工艺制备的Inconel 718高温合金微观组织形态和析出相的影响。结果表明,SLM沉积态合金为椭圆状晶组织,其由细小柱状晶组成。沉积态合金经固溶处理后转变成等轴细晶组织,且随固溶温度升高,晶粒尺寸增大。经固溶+双级时效处理后,合金会在晶界和晶内析出多种析出相,在940~1 020℃固溶过程中晶界析出短棒状δ相(Ni3Nb),在620~720℃时效过程中晶内析出针状δ、圆盘状γ″(Ni3Nb)和黑点状γ′相(Ni3Al,Ti)。     

搅动法细晶铸造K492M合金的显微组织和拉伸性能

采用扫描电子显微镜(SEM)、电子探针(EPMA)和拉伸性能测试等手段,研究了搅动法细晶铸造K492M合金的显微组织和拉伸性能。显微组织观察表明,铸态组织主要包括γ基体、γ′相、碳化物及γ/γ′共晶;热处理后,合金枝晶干和枝晶间处的γ′相由大、小两种尺寸组成,共晶组织未完全溶于基体;碳化物沿晶界析出,呈链状分布。合金在750℃的抗拉强度和伸长率分别为(1157±12)MPa和(9.1±2)%。抗拉断口SEM观察显示,断裂机理主要为韧窝断裂。     

热处理对激光沉积DZ125合金组织与摩擦磨损性能的影响

研究了不同热处理制度对激光沉积DZ125高温合金显微组织、硬度及摩擦磨损性能的影响规律。结果表明：沉积区枝晶形貌为外沿生长的柱状枝晶，平均一次枝晶间距约为10.8μm，经单级时效（870 ℃/20h，AC）和双级时效（1100 ℃/4h，AC to 870 ℃/20h，AC）热处理后，试样的枝晶形貌与沉积态差别不大，γ"相均发生粗化现象，且双级时效热处理后的γ"相粗化程度更高、尺寸分布更为均匀；双级时效热处理制度下，不同低温时效温度γ"相的平均尺寸和含量不同，其中 1100 ℃/4h，AC to 870 ℃/20h，AC制度下，γ"相的平均尺寸和含量最大；经单级时效和双级时效热处理后，碳化物中Ti元素含量均呈下降趋势；双级时效热处理后，析出两种形貌不规则的MC碳化物，分别为富含Cr、Co元素的M23C6型碳化物和富含W、Mo元素的M6C型碳化物；单级时效和双级时效热处理试样的磨损机理均为磨粒磨损，双级时效热处理试样的显微硬度及耐磨性能均优于单级时效。     

固溶温度对一种定向凝固镍基合金中温蠕变性能的影响

通过对一种定向凝固合金进行不同温度的固溶处理、蠕变性能测试及组织形貌观察,研究了固溶温度对枝晶臂/间区域的成分偏析及持久性能的影响。结果表明:经1230℃固溶及时效处理后,合金在枝晶干/间区域存在明显的成分偏析和组织不均匀性,粗大γ'相存在于枝晶间区域,细小γ'相存在于枝晶干区域,碳化物呈条状分布在枝晶间区域。合金经1260℃固溶及时效处理后,可明显降低合金中元素的偏析程度,并消除了合金在枝晶间区域存在中的粗大γ'相,使高体积分数细小立方γ'相均匀分布在枝晶间和枝晶干区域,并有细小粒状碳化物沿晶界析出,抑制晶界滑移,因此,可大幅度改善合金的中温蠕变性能。合金在中温蠕变期间的变形特征是位错在基体中滑移和剪切γ'相,并在γ'/γ两相界面形成位错网。蠕变后期,由于沿与应力轴呈45!角的晶界承受载荷的最大剪切应力,故裂纹易于在与应力轴呈45!角的倾斜晶界处萌生与扩展。     

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。