选区激光和电子束熔化成形纯钨的组织、性能及裂纹形成机理研究

采用选区激光熔化(SLM)和选区电子束熔化(SEBM)技术成形纯钨,对比研究了两种成形方法对纯钨的宏/微观组织和力学性能的影响,利用SEM和EBSD等表征技术,分析了裂纹萌生位置及形成机制。研究结果表明,通过调控纯钨打印过程的工艺参数,可有效地减少 SLM和SEBM成形样品内部的裂纹。SLM和SEBM打印态纯钨的致密度和硬度与输入样品的能量密度呈正比例关系。与SLM相比,SEBM成形时样品内部的温度梯度更低,热应力累积更少,成形后样品中的裂纹更少。SLM打印态样品的内部裂纹多存在于搭接区域,SLM和SEBM制备过程中产生的裂纹均具有沿晶界分布的特征,而且裂纹多萌生于大角度晶界。     

放电等离子烧结制备纯T′相YSZ陶瓷的研究

采用经过等离子喷涂处理的8%(质量分数,下同)YSZ纯T′相陶瓷粉体,经过高能球磨和高能搅拌磨处理后分别在1400、1450、1500、1600℃下进行放电等离子烧结,保温5～15min,得到不同显微结构的陶瓷样品。XRD分析结果显示其仍保持纯T′相。通过对其粉体和烧结后样品显微形貌的分析,探讨晶粒长大与烧结条件的关系,从而得到最优的YSZ纯T′相陶瓷制备工艺为1450℃/5min。     

选区激光熔化专用AlSiMg合金成分设计及力学性能

应用"团簇+连接原子"模型,基于合金液-固局域结构相容性和金属选区激光熔化(SLM)工艺熔体急冷的技术特性,设计高Mg含量SLM专用AlSiMg1.5合金新成分,系统研究时效温度和时间对SLM成形AlSiMg1.5合金显微组织和力学性能的影响。结果表明,通过调整工艺参数,可获得近乎全致密的SLM成形样品。当时效温度为300℃时,随着时效时间的延长,SLM成形样品岛状富Al组织中过固溶Si逐渐析出长大,网格状富Si组织逐渐分解球化,样品的硬度和压缩屈服强度逐渐降低,塑性明显增加。当时效温度为150℃时,不同时效时间下SLM成形样品的显微组织没有发生明显变化,但硬度和屈服强度随时效时间的延长先增大后略有降低。SLM成形AlSiMg1.5样品经150℃时效处理后的最大显微硬度和压缩屈服强度分别为(169±1) HV和(453±4) MPa,样品延伸率超过25%。本工作设计获得了成形性和力学性能优异的SLM专用铝合金新成分Al91.0Si7.5Mg1.5(质量分数,%)。     

选区激光熔化Al-Mg-Sc-Zr合金成形性及力学性能研究

通过选区激光熔化(SLM)技术制备Al-Mg-Sc-Zr铝合金，系统研究了不同工艺参数对铝合金粉末成形性以及不同时效处理条件对SLM成形样品组织和力学性能的影响。结果表明，在高激光功率和低激光扫描速度下，SLM成形样品的致密度较高。沿样品沉积方向可观察到熔池层层堆叠的显微组织，熔池边界和熔池内部均存在细小纳米颗粒。经不同温度时效处理后，样品的硬度和压缩屈服强度先增加后降低。SLM成形样品经400℃时效处理3 h后屈服强度达到最大值469±4 MPa。     

高Mg含量Al-Mg-Sc-Zr合金选区激光熔化成形性及力学性能

基于宽粒径分布粉末(2~46μm),应用选区激光熔化(SLM)技术制备了高Mg含量Al-14.4Mg-0.33Sc-0.19Zr铝合金。系统研究了不同工艺参数和时效处理条件对合金SLM成形性、组织和力学性能的影响。结果表明,高激光功率可有效降低细粉飞溅对样品成形性的干扰,SLM成形样品的最大相对密度为98.6%。样品显微组织由熔池边界细小等轴晶和熔池内部粗大晶粒构成,Mg含量的增加降低了样品织构和柱状晶的含量。经不同温度时效处理后,SLM成形样品的硬度先增加后降低,在350℃时具有最大值。SLM成形样品在350℃时效处理时,硬度和压缩屈服强度均随时效时间的增加出现双峰值现象,时效1 h后样品的硬度(HV)和屈服强度均达到最大值,分别为(1670±30)MPa和(457±10)MPa,延伸率为(27±3)%。样品经350℃长时间时效处理后,由于第二相粒子的粗化,导致样品的硬度和强度有所降低。本研究通过保留铝合金粉末的细粉区,有效提升了粉末的利用率,降低了原料成本,获得了成形性和力学性能较优的高Mg含量SLM成形Al-Mg-Sc-Zr铝合金。     

高Mg含量Al-Mg-Sc-Zr合金选区激光熔化成形性及力学性能

基于宽粒径分布粉末(2~46μm),应用选区激光熔化(SLM)技术制备了高Mg含量Al-14.4Mg-0.33Sc-0.19Zr铝合金。系统研究了不同工艺参数和时效处理条件对合金SLM成形性、组织和力学性能的影响。结果表明,高激光功率可有效降低细粉飞溅对样品成形性的干扰,SLM成形样品的最大相对密度为98.6%。样品显微组织由熔池边界细小等轴晶和熔池内部粗大晶粒构成,Mg含量的增加降低了样品织构和柱状晶的含量。经不同温度时效处理后,SLM成形样品的硬度先增加后降低,在350℃时具有最大值。SLM成形样品在350℃时效处理时,硬度和压缩屈服强度均随时效时间的增加出现双峰值现象,时效1 h后样品的硬度(HV)和屈服强度均达到最大值,分别为(1670±30) MPa和(457±10)MPa,延伸率为(27±3)%。样品经350℃长时间时效处理后,由于第二相粒子的粗化,导致样品的硬度和强度有所降低。本研究通过保留铝合金粉末的细粉区,有效提升了粉末的利用率,降低了原料成本,获得了成形性和力学性能较优的高Mg含量SLM成形Al-Mg-Sc-Zr铝合金。     

多向压缩纯钨烧结体的组织及热稳定性（英文）

对纯度为99.9%的纯钨烧结体在1423 K进行不同压下量的多向压缩(MDC)实验,采用X射线衍射(XRD)、电子背散射衍射(EBSD)及差示扫描量热法(DSC)研究多向压缩前后纯钨试样组织、显微硬度及热稳定性的变化。结果表明,多向压缩后纯钨烧结体位错密度显著增大,压下量50%纯钨试样的位错密度由初始烧结钨的3.08×10~(14)增大至8.08×10~(14) m~(-2),平均晶粒尺寸由83.8μm细化至14.7μm,而显微硬度则由HV0.2 417增大至HV0.2 521。多向压缩后纯钨试样的再结晶温度约为1600 K,近似为常数。纯钨烧结体经多向压缩后由于晶粒尺寸减小以及均匀分布的形核点增多,组织热稳定性得到提高。     

ECAP对SLM纯钛组织演变和力学性能影响

等通道转角挤压（equal channel angular pressing,ECAP）成功对选择激光熔化（selective laser melting, SLM）制备的纯钛进行了改性处理。采用两通道夹角Φ=120°,ψ=20°的模具,在室温下对SLM制备的纯钛进行单道次变形改性处理,并对其显微组织和力学性能进行了评价。结果表明：SLM+ECAP纯钛试样组织细化,晶粒尺寸由13 μm减小到7 μm,位错密度增加。ECAP变形过程中,孪生和连续动态再结晶同时存在,拉伸与压缩孪晶的出现和位错密度的增加共同促使SLM+ECAP纯钛试样显微硬度增加了13%,屈服强度和极限抗拉强度分别提高了18%和20.4%,而延伸率略有减小。     

高密度纯钨的低温活化烧结工艺及其致密化行为

采用溶胶喷雾干燥-煅烧-氢热还原法制备了BET粒径为0.21μm的超细纯钨粉末,并利用球磨处理进一步活化粉末。研究了超细纯钨粉末形貌及其性能随球磨时间的变化特征,探索了未球磨、球磨5h及球磨10h3种超细纯钨粉末烧结致密工艺,此外还详细研究了纯钨烧结体组织形貌、晶粒尺寸及显微硬度等性能随烧结温度及球磨时间的变化规律。结果表明,球磨处理对超细纯钨粉末的烧结起到了极大的活化作用,由球磨10h粉末制成的压块在1900℃下烧结2h其致密度即可达97.3%,比传统微米级纯钨粉末制成的压块达到相同烧结致密度的温度降低了600℃以上。同时,球磨处理可以大幅降低钨粉的起始烧结温度和再结晶温度,获得组织更加均匀细小、力学性能(硬度)更加优良的钨烧结体。     

基于快速多重旋转碾压的纯钛表面纳米化

为了提高纯钛表面的力学性能,采用快速多重旋转碾压(FMRR)技术对其表面进行剧烈塑形变形处理。利用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)及显微硬度计研究了FMRR处理后纯钛表层的微观结构及其硬度。结果表明:FMRR处理后,纯钛的X射线衍射峰均发生明显的宽化,其主要原因是由于剧烈塑性变形导致晶粒细化及产生的微观残余应力所引起的。纯钛经过FMRR处理20 min后,最表层的晶粒被细化到平均大约22 nm,当处理时间增加到40 min时,样品表层的平均晶粒尺寸进一步减小到大约10 nm。处理后样品表层的显微硬度随着处理时间的增加显著提高,最大可达242 HV,比原始样品提高了74%,其主要是由于晶粒尺寸细化及塑性变形引起的加工硬化所致。     

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.     

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.     

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.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

A STUDY OF TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE OF TITANIUM

On the basis of energy and shape method for the determination of the valence bond (VB) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is e_c~(2.9907) · (s_c~(0.4980) d_c~(2.4927)) ef1.0093 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.     

Structural Optimization of Electromagnetic Swirling Flow in Nozzle of Slab Continuous Casting

During the slab continuous casting process, the flow field of molten steel in the mold plays a decisive role in the quality of the slab. In this paper, electromagnetic swirling flow in nozzle technology is proposed to control the flow field in mold.This technology can drive molten steel to rotate inside the submerged entry nozzle by electromagnetic force, thereby controlling the flow field. This research shows that it can reduce the impact of molten steel on the bottom of nozzle and partly reduce the negative pressure at the upper part of nozzle outlet which is even eliminated by optimizing the structure and angle of nozzle. The area of heat flux of the mold wall becomes larger, and the crest value of heat flux gets lower than that without swirling in nozzle and any nozzle optimization. The meniscus fluctuates smoothly, and the flow velocity at the top surface is within a reasonable range. The temperature field distribution in the mold is uniform which was beneficial to the growth of equiaxed crystal and decreased element segregation.     

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).