微量稀土Sm对AZ91D显微组织和腐蚀性能的影响

利用扫描电镜 (SEM) 结合能谱分析 (EDS)、X射线衍射 (XRD)、腐蚀失重实验、电化学极化曲线等方法,研究了0.1%,0.4%,0.7%和1.0%的Sm对AZ91D合金的微观组织和腐蚀性能的影响,并对其腐蚀机理进行分析。结果表明：随着Sm含量的增加,合金中粗大的枝状第二相 (β-Mg₁₇Al₁₂) 逐渐断裂变小,其体积分数下降,因为Sm会结合Al形成颗粒状的Al₂Sm和杆状的Al₃Sm,从而减少晶界处第二相的数量,使第二相呈不连续分布;AZ91D的耐腐蚀性随着Sm加入量的增多,先增加后降低;当Sm加入量为1.0%时,合金的耐腐蚀性与不添加Sm的AZ91D接近;Sm的最佳添加量为0.4%。     

热处理制度对Ti-22Al-25Nb/Ti60双合金焊接接头组织与性能的影响

研究了锻后不同热处理制度对Ti-22Al-25Nb/Ti60双合金焊接接头显微组织和力学性能的影响。结果表明：Ti-22Al-25Nb/Ti60双合金试样经不同工艺热处理后焊缝组织得到不同程度的细化,强度和塑性均得到提高。热处理制度为990 ℃×1 h, AC+750 ℃4 h, AC时,Ti60合金热影响区组织主要由大量细小的等轴α相、少量的片状α相及β转变组织组成,其强度与塑性最佳,且有较好的匹配。     

β相区凝固的铸造γ-TiAl基合金的微观组织(英文)

采用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)及差示扫描量热仪(DSC)研究Ti-43Al-4Nb铸态合金及其热处理态合金的显微组织以及相转变行为。结果表明:通过从β相区凝固的方法可以获得组织细小的铸态Ti-43Al-4Nb合金;凝固过程中γ晶能够直接从β相中形核,β相与γ相沿初始α晶界共存,有效地抑制了铸态Ti-43Al-4Nb合金晶粒的长大;Ti-43Al-4Nb合金在凝固过程中的相转变顺序为L→L+β→β→α+β→α+βr→α+γ+βr→(α2+γ)片层+γ+βr;经1250℃、16h热处理后,Ti-43Al-4Nb合金的显微组织与铸态组织相比有一定程度的粗化;由于Nb元素的充分扩散以及β相的非平衡状态,经过上述热处理过程后残余β相能够被完全消除。     

新型高强度钛合金47Ti-45Zr-5Al-3V退火后的微观组织与力学性能

通过对47Ti-45Zr-5Al-3V合金进行不同温度退火处理,对其微观组织与性能的演变规律进行研究。结果表明,经过高温锻造后的47Ti-45Zr-5Al-3V合金由α+β相组成,在550℃以上温度热处理时合金中α相向β相转变。随温度升高合金中β相含量增加,当温度为800℃时α相全部转变为β相。热处理对47Ti-45Zr-5Al-3V合金的力学性能的影响取决于α相和β相含量。合金抗拉强度随β相含量增加降低,而伸长率增加。     

不同组织类型对TC21合金强-塑性的影响

测试了不同冷却方式下固溶时效后3种组织类型的TC21合金室温拉伸性能,采用金相显微镜和扫描电镜对微观组织进行分析,研究了合金的室温拉伸性能与显微组织的关系。结果表明:强-塑性匹配最好(屈服强度>1000MPa)的热处理制度和组织分别为:920℃/1h,FC+550℃/4h等轴组织;920℃/1h,FC+550℃/4h网篮组织;960℃/0.5h,FC+550℃/4h片层组织。通过调整热处理工艺,控制恰当的α相体积分数、形貌、丛域尺寸及丛域内α条厚度等组织参数,可获得强-塑性匹配良好的TC21合金。     

Ti-43.5Al-4Nb-1Mo-0.3B合金中β相行为和特征

采用元素粉末经热压烧结法制备了新型Ti-43.5Al-4Nb-1Mo-0.3B合金,研究了热处理工艺对合金组织中β相转变行为及其力学性能的影响。结果表明,粉末冶金态Ti Al合金中β相呈条带状,与γ相形成块状组织。热处理能显著改善材料的组织均匀性,使B2/γ块状组织逐渐转变成α_2/γ层片组织,β相转变行为特征为吸收Ti、Al元素,排出Nb元素。温度是热处理过程中组织均匀化的主控因素,在共析温度Te附近热处理时(1100~1160℃/24 h),B2相逐渐溶解但不能完全消除,而在α相转变温度Tα以上短时热处理和稳定化低温热处理后,如1400℃/2 h/FC+850℃/6 h/AC,B2/γ块状组织可完全消除,且组织粗化不严重。初始态B2相纳米硬度为6.69 GPa,弹性模量为175.4 GPa,热处理导致其纳米硬度和弹性模量逐渐降低。     

成分和冷却速度对Al-xEr合金凝固组织的影响

用扫描电镜(SEM)和X射线衍射仪(XRD)分析了Al-xEr(x=10、20、30,质量分数,%)合金凝固组织的形貌和相结构。结果表明,在60 ℃/h的冷却速率下,Al-10Er合金中Al₃Er相为L1₂结构,尺寸约为200 μm,相与相之间以鱼骨状连接。当Er含量增大到30%时,初生Al₃Er相呈块状,尺寸约为1 mm。对Al-30Er合金,随冷却速率的降低,初生Al₃Er相由轮廓平直的L1₂结构转变为轮廓呈波浪状的hR20结构,同时共晶组织由絮状转变成条状。     

一种新型易变形Ti-Al-Mn-W合金组织与力学性能

设计并制备了一种新型低成本、易热变形的Ti-43Al-3.5Mn-0.5W(at%)合金锻锭,并对其组织、室/高温拉伸力学性能、抗高温氧化性、热变形能力进行了系统分析。结果表明,与Ti-42Al-5Mn相比,研制的合金强度、抗高温氧化性、热变形能力更佳,且该合金α₂和β_o相中具有更低的Mn含量,降低了合金近服役温度下富锰Laves相的析出倾向。合金的固态相变路线为：β→β+α→β+α+γ→β+β_o+α+α₂+γ→β_o+α₂+γ,其中γ相完全溶解的温度(T_γ-solv)约为1250℃,β单相区温度(T_β或T_α)约为1360℃。锻态合金显微组织为α₂/γ片层和片层界面处大量β_o和γ混合相,高温强度降低明显。通过两步热处理,锻态合金的高温强度和稳定性均有一定提升,这主要归结为片层组织含量的提高和片层晶团尺寸的细化。1260℃/0.5 h/AC+800℃/...     

固溶时效热处理对医疗器械用TA4合金组织与性能的影响

对B和C微合金化的Ti-3.5Al-5Mo合金医疗器械进行了固溶与时效热处理,观察了不同热处理制度下钛合金的组织与力学性能变化。结果表明,经过固溶与时效热处理的钛合金中出现了细小的Ti B相或者Ti C相,并且可以有效抑制合金中β晶粒的长大,同时还存在细小的次生α相;当时效热处理制度选定为550℃×6 h时,随着固溶温度的上升,抗拉强度和屈服强度逐渐降低,断后伸长率和断面收缩率也表现为逐渐降低的趋势;在790℃×1.5h固溶+550℃×6 h时效时可以取得最好的强度与塑性结合。     

Mg-6Al-2Nd-xCa系耐热镁合金凝固路径分析

以Mg-Al-Nd-Ca合金为研究对象,通过测定不同Mg-6Al-2Nd-xCa合金(x=0、0.5、1.0、1.5、2.0、2.5、3.0,%,质量分数)凝固曲线,并通过重熔-等温液淬试验及XRD、OM、SEM、EDS等分析手段,研究了Ca对Mg-6Al-2Nd合金相形成及凝固路径的影响。结果表明,随着Ca含量增加,Al₁₁Nd₃和β-Mg₁₇Al₁₂相含量减少,Al₂Ca相增多。α-Mg、Al₂Nd、Al₁₁Nd₃相的析出温度均随Ca含量的升高而降低,其中α-Mg相的析出温度由620℃下降至606℃,Al₂Nd相的析出温度由630℃下降至610℃,而Al₂Ca相的析出温度则由504℃升高至529℃。Mg-6Al-2Nd-xCa(x=0、0.5,%)合金的凝固路径为L→Al₂Nd;L→α-Mg;L_Al+Al₂     

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.     

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.