机械合金化制备Ni-Ti合金粉末

研究了在机械合金化制备Ni粉和Ti粉并将之混合的过程中,球磨工艺,即球磨时间和球磨转速对粉末粒度的影响,并对粉末进行了XRD相分析.结果表明,以260r/min转速球磨60 h可以合成Ni-Ti非晶粉末,在氩气保护下于530℃×30 min退火可使Ni-Ti非晶粉末晶化.     

MA制备W-Ni-Fe纳米复合粉末的工艺优化

研究了90W-7Ni-3Fe混合粉末在行星式高能球磨机中的机械合金化(MA)工艺.在一定条件下球磨后,采用XRD分析了粉末相变化、晶块尺寸和晶格畸变,采用SEM对粉末形貌进行了分析.研究了球磨时间、球磨机转速、球料比、球装填系数、不同的表面活性剂等因素对粉末性能的影响.确定了机械合金化制备W-Ni-Fe纳米复合粉末的最优化工艺:球磨转速为200r/min,球装填系数为6%～12%,球料比为10∶1,液体介质比为V液体∶V(球 料)=1.4～2.0.不同种类的过程控制剂对MA粉末分散和粉末的成形性有很大的影响,采用8#过程控制剂能在有效分散MA粉末的同时具有好的成形性.     

机械合金化法制备Ti_(50)Ni_(15)Cu_(28)Sn_7非晶合金粉末

以一定比例配置Ti、Ni、Cu、Sn金属粉末,利用机械合金化方法在转速为300 r/min、球料比为12∶1的条件下制备Ti_(50)Ni_(15)Cu_(28)Sn_7非晶合金。采用XRD和SEM对不同球磨时间混合粉末的物相结构和形貌进行分析。并对合金粉末进行了DSC分析。结果表明:经过不同时间球磨之后,混合的金属粉末开始出现合金化及不同程度的非晶化。随着球磨时间的增加,粉末颗粒逐渐细化。球磨80 h后,合金粉末全部转变为非晶合金,且具有较高的热稳定性和非晶形成能力。     

高能球磨法制备Fe-C超细晶/纳米晶粉末的研究

采用高能球磨法制备出了平均颗粒尺寸为纳米级的超细Fe-C粉末。利用SEM、XRD等分析手段研究了球磨时间和转速对Fe-C超细晶/纳米晶粉末颗粒形貌、尺寸和合金化效果的影响。结果表明,Fe-C超细晶/纳米晶粉末的过程中,颗粒尺寸随球磨时间和转速的增加而得到有效细化。当球料比为20:1、转速350r/min、球磨70 h时,颗粒细化效果最好。将球磨后平均颗粒尺寸为纳米级的粉末进行SPS烧结,烧结温度700℃时,能实现烧结体完全致密,并可有效避免晶粒的长大,该烧结体材料抗压强度达2800MPa。     

Ti_(44)Ni_(47)Nb_9合金粉末球磨工艺的优化

采用机械合金化的方法制备了Ti_(44)Ni_(47)Nb_9形状记忆合金粉末,采用X射线衍射(XRD)、扫描电镜(SEM)分析和能量色散光谱(EDS)等分析了球磨工艺参数对粉末非晶度和颗粒尺寸的影响,得出了最佳的球磨工艺参数。分析了球磨转速、球料比以及球磨时间等参数对机械合金化过程的影响规律。结果表明:合金粉末在球磨60 h时已出现大部分非晶相,100 h时已接近完全非晶化。机械合金化制备的Ti_(44)Ni_(47)Nb_9合金粉末尺寸随球磨时间的增加先迅速减小后在60 h左右趋于稳定,在球磨速率不变的条件下,随着球磨时间增长,粉末的平均粒径大幅度减小,且由棱角分明的不规则体逐渐变化为球形体,在球磨初期(10～30 h)存在颗粒团聚的现象,随球磨时间延长(30 h后)该现象逐渐消失。从粉末颗粒尺寸、分布状况、圆滑程度等方面分析考虑:在球磨时间为100 h的条件下,当球磨转速为200 r/min、球料比为10∶1时机械合金化效果最佳。     

球磨参数对机械合金化制备碳化硅粉体的影响

通过热力学计算分析石英与石墨反应的可行性。研究了机械合金化石英与石墨混合粉末的过程中,球磨工艺（球磨时间、球料比）对机械合金化过程的影响。试验结果表明,采用球料比50：1,球磨机转速为300r／min,球磨时间为72h时,体系提供了足够的能量生成碳化硅。     

机械合金化Nb-Cr粉末的热力学分析

在球、料质量比为13∶1的条件下对Nb-Cr二元粉末进行了高能球磨,研究了摩尔比为1∶2的Nb、Cr混合粉末的机械合金化（MA）过程,用X射线衍射（XRD）分析了球磨粉末的物相组成.结果表明,球磨20 h后粉末变化为先形成Nb（Cr）的过饱和固溶体,45 h后逐步形成非晶,进一步球磨,159 h后发生非晶的晶化.参考Miedema半经验模型理论,建立了Nb-Cr系MA过程的热力学模型.该模型的计算结果表明,Nb-Cr二元系具有形成非晶、固溶体和化合物的热力学驱动力.对摩尔比为1∶2的Nb、Cr混合粉末不同时间XRD结果进行了分析,发现与热力学计算结果吻合.     

金刚石抛光用W-Mo-Cr合金粉末的机械合金化工艺研究

采用机械合金化(MA)方法制备W-Mo-Cr混合粉末,并研究了机械合金化中的工艺参数对粉末性能的影响。球磨实验后,用X射线衍射仪(XRD)分析粉末的物相、晶粒尺寸和晶格畸变,用扫描电镜(SEM)分析粉末的微观形貌,用激光粒度分布仪分析粉末颗粒的大小及分布,用X射线荧光光谱(XRF)分析混合粉末中各成分的含量。结果表明,当球料比为15∶1,球磨转速为250 r/min,球磨介质比为1∶1,球磨45 h,所制备出的混合粉末晶粒尺寸较小,成分均匀,杂质少,可提高合金抛光盘的致密度、硬度和耐磨性。     

纳米晶W粉和W-Ni-Fe预合金粉的制备

采用高能球磨法制备纳米晶W粉和W-Ni-Fe预合金粉，研究了不同的球磨材质包括硬质合金球(CCB)、钨球(TAB)和球磨转速、球料比及球磨时间等条件对球磨后粉末性能的影响。利用XRD，TEM和EDX分析球磨后粉末的晶粒尺寸、晶格畸变、形貌、结构变化及颗粒成分变化。结果表明：高能球磨法可制得10nm～80nm的W粉和W-Ni-Fe预合金粉，纳米级颗粒含量达80％以上。相同材质的钨球制得的纳米粉末综合性能较好。球磨过程中，粉末保持颗粒状结构，纳米级粉末颗粒形状最终趋于等轴化。     

Mg_3Sb_2金属间化合物的机械化学合成工艺

采用机械合金化方法制备Mg_3Sb_2金属间化合物,研究了摩尔比为3:2的Mg、Sb混合粉末的机械合金化过程,通过改变球磨转速和球料比找到制备Mg_3Sb_2的最佳工艺参数,对球磨后的粉末进行了X射线衍射(XRD)、差示扫描量热法(DSC)、扫描电镜(SEM)测试分析。结果表明,机械合金化方法可制备出细小的Mg_3Sb_2粉末,最佳球磨工艺参数是500 r/min的球磨转速、15:1的球料比。由热力学计算可知,Mg-Sb二元合成反应的绝热温度Tad=2149.5 K。DSC分析知,随球磨时间的延长,燃烧反应的临界温度会下降。经Kissinger公式计算原始混合粉末的激活能为94.45 k J/mol,球磨2 h之后的激活能为82.23 k J/mol,说明球磨使粉末内部产生大量晶体缺陷和位错等,体系能量增加,反应激活能降低,从而促进合金化的进程。     

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.