Cr含量对Er2Fe17-xCrx合金相结构与微波吸收性能的影响

采用非自耗电弧熔炼炉制备了Er₂Fe_17-xCr_x(x=0、1、2、3、4)合金,借助X射线衍射仪（XRD）、扫描电镜（SEM）和网络矢量分析仪（VNA）研究了Cr的加入量对Er₂Fe₁₇合金相结构及微波吸波性能的影响。结果表明,x=0、1、2时,合金主要由单相Er₂Fe₁₇组成;继续增加Cr的含量,当x=3、4时,合金由Er₂Fe₁₇和Er₆Fe₂₃两相组成。当吸波涂层厚度d=2 mm时,Er₂Fe_17-xCr_x（x=0、1、2、3、4）合金的最小吸收峰值在9、13、14.5、15.8和16.8 GHz处分别达到－17.5、－20、－39.2、－17和－15 dB;吸收峰频率随着Cr含量的增加,向高频方向移动。随着吸波涂层厚度的增加,Er₂Fe₁₄Cr₃试样的吸收峰频率向低频方向移动,吸收峰值先减小后增大,最佳匹配条件出现在d=2 mm处。     

退火温度对FeMoCrVTiSix高熵合金组织及力学性能的影响

在400、600、800、1100 ℃下对FeMoCrVTiSi_x(x=0、0.3)进行退火处理,利用X射线衍射仪、扫描电镜、差热扫描分析仪、显微硬度计、万能试验机等探究了不同退火温度对合金的组织和力学性能的影响。结果表明,Si元素的添加提高了FeMoCrVTi高熵合金的热稳定性。经过退火处理,FeMoCrVTiSi_x高熵合金的微观组织仍为以BCC固溶相为主的枝晶结构,但在枝晶边缘出现黑色的细小富Ti相,其含量随着退火温度的增加而增多,在1100 ℃下富Ti相回溶。富Ti相的析出提高了合金的硬度,其中,800 ℃退火后试样的硬度达到最大值,FeMoCrVTi试样的硬度达到932 HV0.2,FeMoCrVTiSi_0.3的硬度达到998 HV0.2。     

激光熔覆AlxNbMn2FeMoTi0.5高熵合金涂层的组织与性能

使用激光熔覆技术在Q235钢基体上制备Al_xNbMn₂FeMoTi_0.5高熵合金涂层,期望借此提高干切削技术适用刀具表层的硬度和耐磨性。经过初步筛选之后,主要研究了Al_xNbMn₂FeMoTi_0.5(x=1、1.5、2)高熵合金涂层体系,并采用XRD和3D激光扫描成像等手段分析了不同Al含量的Al_xNbMn₂FeMoTi_0.5合金涂层的晶相结构、显微组织和具体元素分布。结果显示,对于Al_xNbMn₂FeMoTi_0.5高熵合金涂层,随着Al含量的增加,涂层的相结构由单一的BCC相逐渐转变为双相BCC结构,晶粒逐渐细化。当x=2时,Al_xNbMn₂FeMoTi_0.5高熵合金涂层硬度最高,平均为1089.6 HV0.3,大约为基材的5倍,且其具有最优的耐磨损性能。x=1.5时,Al_xNbMn₂FeMoTi_0.5高熵合金涂层的自腐蚀电位最高,自腐蚀电流密度最小,耐腐蚀性最好。     

硼对铸态Al0.3CoCrFeNi高熵合金组织及性能的影响

采用冷坩埚悬浮熔炼法制备了Al_0.3CoCrFeNiB_x(x=0,0.01,0.05,0.1)系列高熵合金。利用X射线衍射仪、电子背散射衍射分析、扫描电子显微镜及附带的波谱仪分析了B的添加对Al_0.3CoCrFeNi合金组织结构的影响,研究了Al_0.3CoCrFeNiB_x合金的显微硬度、室温摩擦磨损性能及室温压缩性能。结果表明:Al_0.3CoCrFeNi合金为fcc结构,随着B含量的增加,fcc相基体中晶界处Cr₂B析出相逐渐增多,且Cr₂B相由颗粒状分布逐渐转变为连续网状分布,致使合金的硬度、耐磨性和屈服强度均逐渐提高。可见,Cr₂B析出相弥散强化作用显著,Al_0.3CoCrFeNiB_0.1综合性能更佳。     

热处理对Y2O3掺杂WC-Co硬质合金显微组织及性能的影响

采用固液掺杂法和放电等离子烧结制备了WC-Co-Y₂O₃硬质合金，随后对其进行了不同温度的退火处理。采用光学显微镜、X射线衍射仪(XRD)、扫描电镜(SEM)和维氏硬度计等研究了热处理前后WC-Co-Y₂O₃硬质合金的显微组织和力学性能。结果表明：氧化钇的加入可以细化WC-Co-Y₂O₃合金中的WC晶粒，提高了合金的维氏硬度和断裂韧性；随着退火温度的升高，WC-Co-Y₂O₃合金的维氏硬度逐渐降低，断裂韧性先升高后降低；WC-Co-Y₂O₃合金在500℃退火时拥有最佳的综合性能，维氏硬度为(1377±15) HV30,断裂韧性为(13.0±0.4) MPa·m^1/2。     

预氧化处理对MP35N合金高温氧化行为的影响

目的 探索并优化合金成分、工艺以获得致密稳定的预氧化膜,提高合金抗氧化能力。方法 利用非自耗真空电弧炉熔炼合金,在真空容器中加热金属及其氧化物粉末获得平衡氧压。通过莱茵装置进行预氧化实验。通过FactSage计算Co-Ni-Cr-Mo-Al-Si体系的合金组织相图及其氧化相图,利用X射线衍射(XRD)和扫描电子显微镜对预氧化的试样进行物相分析。结果 在1000℃、10^–17atm氧压下预氧化,未含Si的MP35N合金表面出现Cr₂O₃氧化物;随着Si添加量的增加,表面氧化物变为(Al,Cr)₂O₃,以Cr₂O₃为主,内氧化物为Al₂O₃;当Si含量(质量分数)为3%时,内部形成了近乎连续的带状Al₂O₃氧化膜。在1 000℃、10^–25 atm氧压下,合金表面形成连续的Al₂O₃膜;...     

Mn含量对Zn-Al-Mg合金组织和耐腐蚀性能的影响

为了使热镀锌产品获得更好的耐腐蚀性能,通过感应熔炼制备了3种不同Mn含量的Zn-Al-Mg合金铸锭,分别为Zn1Al1Mg0.5Mn、Zn1Al1Mg1.2Mn、Zn1Al1Mg2.5Mn,并分析了其凝固组织和腐蚀行为。结果表明：通过相图计算预测了含Mn的Zn-Al-Mg合金中Al-Mn化合物类型为Al₁₁Mn₄、Al₈Mn₅、Al_0.8Mn; Zn1Al1Mg0.5Mn、Zn1Al1Mg1.2Mn合金的Al-Mn析出相分别为Al₁₁Mn₄、Al₈Mn₅,随着Mn含量的增加,Zn1Al1Mg2.5Mn合金中的Al-Mn析出相为Al₈Mn₅和Al_0.8Mn,其中Al₁₁Mn₄和Al₈Mn₅相主要在共晶组织中析出,Al_0.8     

Si含量对WMoNbCrTi高熵合金微观组织和力学性能的影响

WMoNbCrTi高熵合金是一种极具应用潜力的高温结构材料，添加Si有望提高其综合力学性能。以高能球磨粉末为原料，采用放电等离子烧结技术制备了WMoNbCrTiSi_x(x=0、0.1、0.25和0.5)高熵合金，研究Si含量对其微观组织和力学性能的影响。结果表明：加入Si后高熵合金的组织由BCC固溶体、Laves相和硅化物组成。当x=0.1时，Si主要形成Ti₅Si₃,当x=0.25时，大部分Si与Ti形成Ti₅Si₃,少部分Si与Nb形成Nb₃Si,当x=0.5时，Si主要形成Ti₅Si₃、Nb₃Si和Cr₃Si。当x从0增加到0.5时，WMoNbCrTiSi_x高熵合金的硬度由9.84 GPa增加到13.46 GPa,断裂韧性从6.68 MPa·m^1/2下降到4.72 MPa·m^1/2。WMoNbCrT...     

三元Laves相Cr-Nb-Si(Al)合金的组织演变与强韧化机理

采用真空非自耗电弧熔炼法制备了两种系列的Laves相Cr-Nb-Si(Al)合金,利用扫描电镜(SEM)、能谱仪(EDS)、Vickers硬度计及万能力学试验机研究了合金的显微组织、力学性能及强韧化机理。结果表明：随着Al含量不断增加,合金Cr-45Nb-xAl(x=0,7.5,17.5)的显微组织由初生相Cr₂Nb+共晶Cr₂Nb/Nb固溶体(Nbss)演变为全共晶Cr₂Nb/Nbss;而随着Si含量不断增加,合金Cr-57.5Nb-xSi(x=0,5,10)的显微组织由初生相Nbss+共晶Cr₂Nb/Nbss演变为海藻-树枝晶共晶,树枝晶内部为两相共晶Cr₂Nb/Nbss,树枝晶边缘为三相共晶Cr₂Nb/Nb₅Si₃/Nbss。合金Cr-45Nb-xAl(x=0,7.5,17.5)的压缩强度与断裂韧性随Al含量增加不断减小,而合金Cr-57.5Nb-xSi(x=0,5,10)的压缩强度与断裂韧性随Si含量增加...     

Tix(AlNbZr)100-x系多主元合金力学性能的第一性原理研究

通过对合金的固溶体参数以及相比例图进行计算,研究了Ti_x(AlNbZr)_100-x系多主元合金的固溶体相形成规律,运用基于密度泛函理论的第一性原理方法研究了Ti含量变化对Ti_x(AlNbZr)_100-x系多主元合金结构稳定性以及力学性能的影响。结果表明,Ti_x(AlNbZr)_100-x系多主元合金可以形成稳定的固溶体相,且合金主要由BCC相和Al₃Zr₅相组成,随Ti含量增加,合金的液相线降低,Al₃Zr₅相的相形成温度减小,直到Ti含量为60%~70%时,Al₃Zr₅相消失,合金由单一BCC相组成;Ti含量增加可以提高合金的结构稳定性,当Ti含量为25%~70%时,合金具有良好的力学稳定性,合金的体积模量、剪切模量以及杨氏模量随着Ti含量的增加呈上升趋势。Ti_x(AlNbZr)_100-x系多主元合金的基态能量和形成热随着Ti含量的增加而降低,表明增加Ti含量可以增加该合金系的热力学稳定性,使合金更易形成固溶体相。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.