磁兼容Au-25Pt合金的组织结构及综合性能

Au-Pt合金具有优异的MRI磁兼容性、良好的生物兼容性、高的耐蚀性等优点,在医用材料领域具有巨大的应用前景。采用X射线衍射仪、金相显微镜、维氏显微硬度仪和综合物性测量系统等,研究冷加工过程Au-25Pt合金丝材的组织结构演变及其对体积磁化率和维氏硬度的影响,为制备综合性能优异的Au-Pt合金探索有效途径。结果表明,固溶处理后的Au-25Pt合金为面心立方结构的单相固溶体,经30%～70%冷变形后,没有其它相产生。冷加工变形显著增加了Au-25Pt合金的维氏硬度,尤其在冷加工初期(<30%变形量),但对磁化率影响很小。冷变形Au-25Pt合金不仅具有接近人体组织的体积磁化率(-8.5×10-6),还有较高的维氏硬度(HV0.1=160)。     

热轧和退火对Au-20Sn合金箔材组织和性能的影响

采用热轧方法制备了Au-20Sn合金箔材,研究轧制和退火处理对合金箔材微观组织和硬度的影响.结果表明,铸态Au-20Sn合金组织由枝晶状Au5Sn初生相及交替生长形成的片层状共晶组织组成.铸态合金经热轧后发生了动态再结晶,粗大的片层状共晶组织转变为沿轧制方向拉长的两相组织.经退火处理,合金热轧组织逐渐转变为均匀的等轴状...     

退火处理对CoFeNiVTi高熵合金组织和性能的影响

采用真空电弧炉熔炼和铜模吸铸法制备了CoFeNiVTi高熵合金柱状试样，并对其在氩气保护条件下进行了800℃退火20 h的处理。利用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)和压缩实验等研究了铸态和退火态CoFeNiVTi合金的显微组织和力学性能。结果表明：铸态合金为单相BCC固溶体结构，显微组织呈现典型的柱状晶特征，合金元素均匀分布；退火态合金由BCC基体和金属间化合物Ni₂V₃型的σ析出相构成，σ析出相具有明显的取向特征，呈粗大板条状和细小针状。与铸态合金相比，由于σ析出相的存在，退火后合金的断裂强度有所下降，但仍高达2.5 GPa,硬度则显著提高至800 HV0.2。     

铸态和退火态Al_(0.5)CoCrFeNiTi_(0.5)高熵合金的组织与性能

采用真空电弧熔炼法熔炼出Al_(0.5)CoCrFeNiTi_(0.5)高熵合金,并在600、800和1000℃下进行真空退火热处理。利用X射线衍射仪(XRD)、光学显微镜(OM)、电子探针(EPMA)、硬度计、万能试验机以及电化学工作站对合金铸态和不同温度退火态的微观组织、硬度、压缩力学性能以及在3.5%NaCl溶液中的耐蚀性进行研究。组织分析表明:铸态和退火态的Al_(0.5)CoCrFeNiTi_(0.5)合金均由富(Cr,Fe)的FCC、富(Al,Ni,Ti)的BCC和σ三相组成,但退火处理使合金的组织形貌和各相的相对含量发生了改变,铸态下的粗大白色FCC柱状晶转变为细小的FCC+BCC+σ的混合组织;随着退火温度的升高,BCC和σ相含量增加。800℃退火态合金成分均匀性最好,1000℃退火态合金由于退火温度过高,组织粗大,元素偏析重新加剧。硬度试验和压缩试验结果表明:合金在铸态和3种温度退火态下的硬度都较高,表现出良好的抗回火软化能力;800℃退火态合金中由于BCC和σ相的增加,其硬度和屈服强度最高,但塑性最差。1000℃退火态合金由于大量σ相的析出以及组织粗大,其屈服强度、断裂强度和压缩形变率都急剧降低。600℃退火态合金具有理想的FCC、BCC和σ相的组成含量,其综合力学性能最好。电化学腐蚀试验表明:铸态和3种温度退火态的合金在3.5%NaCl溶液中都表现出良好的耐蚀性,800℃退火态合金由于其成分均匀性最好,耐蚀性最好。     

Er、Zr微合金化5083铝合金的超塑性

针对5E83合金(Er、Zr微合金化5083合金),采用超塑性拉伸试验、扫描电镜(SEM)、电子背散射衍射(EBSD)和透射电镜(TEM),探究了Er、Zr微合金元素、晶粒尺寸、变形温度、应变速率对合金超塑性的影响。通过再结晶退火、空冷和水冷的搅拌摩擦加工(FSP),分别获得了晶粒尺寸为7.4、5.2、3.4μm的完全再结晶组织,作为初始状态进行超塑性拉伸。结果表明,初始晶粒尺寸越细小,超塑性伸长率越高。当晶粒尺寸>5μm时,超塑性变形过程晶粒粗化缓慢,细化初始晶粒可显著提高超塑性;而当晶粒尺寸<5μm时,超塑性变形过程晶粒粗化严重,进一步细化初始晶粒对超塑性的提高有限。不同变形温度、应变速率的超塑性拉伸结果显示在变形温度为450～540℃、应变速率为1.67×10^-4～1.67×10^-1 s^-1,超塑性伸长率随变形温度和应变速率的提高呈现先上升后下降再上升的趋势;变形温度为520℃、应变速率为1.67×10^-3 s^-1条件下,水冷FSP态合金获得最大伸长率330%...     

Au-12Ge钎料箔材的工艺集成制备与组织演化研究

Au-12Ge共晶合金传统生产工艺操作复杂,重复性差,成品率低。本文采用一体式加工工艺,制备出厚度为20 μm的箔材钎料。采用扫描电子显微镜(SEM)研究Au-12Ge共晶合金铸态、不同轧制变形量的显微组织形貌,采用同步热分析仪(DSC)研究Au-12Ge箔材的共晶转变温度。结果表明,Au-12Ge共晶合金的铸态组织为Au相和Ge相,随着热轧变形量的增大,Au-12Ge共晶合金组织Ge相经历细化分散到粗化过程,粗大的Ge晶粒内部包裹软质的Au相;Au-12Ge共晶合金箔材的熔点为361℃。     

球化时间对AZ80镁合金组织及力学性能的影响

通过光学显微镜、场发射扫描电镜、X射线衍射(XRD)、硬度测试及拉伸试验等手段,研究了球化处理时间对AZ80析出相β-Mg17Al12及力学性能的影响。结果表明,铸态AZ80合金经退火处理后,晶间粗大的网状共晶β相消失,得到细小层片状脱溶β相均匀分布于α-Mg基体中。随球化时间延长,层片状β相开始溶断,先出现短棒状,然后向球状过渡,球化16h时镁基体上弥散分布大量细小颗粒状β相。继续延长时间,颗粒状β相出现溶解,数量减少,合金的综合性能最佳,屈服强度、抗拉强度和伸长率分别是132.5 MPa、252.4 MPa和9.56%。合金硬度随球化时间延长呈先升后降的变化规律,且均高于铸态合金。     

热处理对AZ91D镁合金显微组织的影响

研究了铸态、同溶及时效AZ91D镁合金的微观组织,分析了热处理对合金组织和显微硬度的影响.结果表明.薄片状共晶α相和粗大块状B相的热稳定性都不高,但可分别经过380和410℃同溶处理加以消除;Al-Mn相主要呈颗粒状或针状,尺寸为10～50 μm.经410℃×24 h固溶处理未发生明显改变.固溶样品经200℃×12h时效后有大量长10μm、直径1～2μm的杆状相析出.且主要垂直或斜交于基体,但当时效温度继续升高时析出相将转变为大部分平行于基体分布,使第二相的强化效果减弱.     

球化处理对AZ80镁合金析出相β-Mg_(17)Al_(12)及力学性能的影响

采用场发射扫描电镜(FESEM)、光镜(OM)、X射线衍射(XRD)、布氏硬度及拉伸实验等方法研究了球化处理对AZ80析出相β-Mg17Al12及力学性能的影响。结果表明:铸态AZ80合金经过415℃保温24 h随炉缓冷的退火处理后,晶间粗大的网状共晶β相消失,得到细小层片状脱溶β相均匀分布于α-Mg基体的平衡组织,且片层状间距致密。球化处理中,层片状β相以自身溶断方式实现球化;经300℃球化处理后镁基体上弥散分布大量细小颗粒状β相,继续升温,颗粒状β相发生二次固溶,数量减少。球化处理后合金的屈服强度、抗拉强度最大达135.4 MPa和258.7 MPa,较铸态合金分别提高了19.1%和59.6%,伸长率由铸态的4.96%上升至9.88%。布氏硬度HB随球化温度的升高呈现先增高后降低的变化规律,且均高于铸态合金。     

热处理对Cu-0.8Cr-0.15Zr-2.8Co-0.7Si-0.1RE合金组织与性能的影响

采用金相显微镜、扫描电镜、能谱仪、X射线衍射仪等测试手段,研究了热处理对Cu-0.8Cr-0.15Zr-2.8Co-0.7Si-0.1RE合金显微组织、电导率和硬度的影响。结果表明,合金铸态组织为粗大的等轴晶,基体分布着大量Co_5Cr_3Si_2相和Co、Si组成的灰色析出相;固溶处理后,晶粒明显长大,灰色析出相完全溶解,Co_5Cr_3Si_2相并未溶解;时效处理后,析出相主要有Co_5Cr_3Si_2、Co_2Si等。随固溶温度升高,合金电导率快速下降,硬度快速上升。时效处理后,合金电导率、硬度值都有大幅提高。经980℃×2h固溶+450℃×10h时效后,硬度(HV)达到218.9,电导率达到28.54 MS/m,软化温度达到686℃。     

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。