放电等离子烧结-热变形技术制备NdFeB永磁材料

采用放电等离子烧结(SPS)方法烧结HDDRNdFeB粉末,研究烧结温度对制备NdFeB永磁材料密度和磁性能的影响。随着烧结温度在650～900℃范围内升高,剩磁、内禀矫顽力及最大磁能积均呈现先升后降的趋势。800℃烧结所获得磁体的磁性能最佳:Br=0.78T,Hcj=577kA/m,(BH)max=78kJ/m3,其致密度达到了99%。微观组织、XRD图谱及磁性能均表明800℃烧结的磁体出现了一定程度的各向异性。900℃烧结时,晶粒长大明显。进而选择具有最佳磁性能的磁体在800℃进行热变形(HD)处理,制备出各向异性磁体。热变形制备的磁体中,大部分晶粒为扁平片状且c轴取向与热压方向一致;少量异常长大晶粒会使细小Nd2Fe14B晶粒的c轴偏离压力方向。各向异性磁体沿c轴的磁性能为:Br=1.09T,Hcj=384kA/m,(BH)max=114kJ/m3。     

放电等离子烧结-热变形各向异性Nd-Fe-B磁体的微观组织及磁性能

采用放电等离子烧结及后续热变形技术制备各向异性Nd-Fe-B磁体,研究烧结温度对放电等离子烧结Nd-Fe-B磁体微观组织和磁性能的影响。随着烧结温度在650~900°C范围内的升高,烧结态Nd-Fe-B磁体的剩磁、内禀矫顽力及最大磁能积呈现先升后降的趋势。在800°C下烧结所获得磁体的磁性能最佳。随后,对800°C烧结后具有最佳磁性能的磁体采用放电等离子烧结技术进行后续热变形处理。与初始吸氢-歧化-脱氢-再复合粉末和烧结态磁体相比,热变形磁体拥有更显著的各向异性和更好的磁性能。当热变形温度为800°C且压缩比为50%时,热变形磁体中的Nd2Fe14B晶粒呈扁平片状且不发生异常长大;磁体沿热压方向具有最佳的磁性能：Br、Hcj和（BH）max分别为1.16 T、449 k A/m和178 k J/m3。     

块状纳米晶SmCo5烧结磁体的结构及其磁性能

采用放电等离子烧结(SPS)技术制备致密块状纳米晶SmCo5烧结磁体,研究磁体的结构和磁性能.XRD结果表明:球磨粉末基本为非晶结构,烧结磁体具有CaCu5结构.TEM结果表明:磁体获得晶体均匀分布的组织结构,平均晶粒尺寸约为30 nm.电子选区衍射(SAED)分析表明:磁体主相为SmCO5相.室温时磁体的矫顽力高达2.28 MA/m,而剩磁比Mr/Ms高达0.7,并通过剩磁曲线-M-H及其变化趋势,说明在纳米晶之间存在强烈的晶间交换耦合作用.烧结磁体具有良好的高温性能,773 K时其矫顽力为0.72 MA/m,矫顽力温度系数β为-0.146%/K.     

后热处理工艺对放电等离子烧结制备NdFeB磁体的影响

放电等离子烧结(SPS)技术是制备NdFeB合金材料的一种新型工艺方法。本文研究了后热处理工艺对放电等离子烧结制备NdFeB磁体磁性能的影响，同时考察了后热处理工艺对SPS NdFeB磁体微观组织结构和尺寸精度的影响。在适当的后热处理工艺条件下，得到了细晶高性能NdFeB磁体。结果表明可以通过后热处理进一步改善SPS烧结磁体的磁性能，论证了采用SPS技术制备近净成形的细晶高性能NdFeB磁体是完全可行的。     

SPS制备SmCo7-xFex块状纳米晶磁体的研究

采用高能球磨法制得SmCo7-xFex非晶粉末,然后采用放电等离子技术将其烧结为块状纳米晶磁体,对磁体的微观结构和磁性能进行了观察和测试.结果表明,SmCo7-xFex球磨5 h后成为非晶粉末,经SPS烧结后得到1:7相.TEM观察表明,磁体晶粒尺寸在20～50 nm.另外,磁体具有较好的磁性能,当x=0.4时,矫顽力为992.8 kA/m,剩磁为0.634T,(BH)max为69.75KJ/m3.     

DyF<sub>3</sub>掺杂热变形NdFeB磁体的微观结构和性能

基于热变形技术,研究制备了DyF3掺杂热变形NdFeB磁体的微观结构和磁性能。结果表明,通过热变形,磁体获得了具有明显C轴取向特征的扁平形状晶粒,其剩磁从前驱体烧结磁体的0.77 T提高至 1.34 T,提升了近74%。此外,热变形过程起到了晶界扩散的作用,使得DyF3进一步扩散至NdFeB主相之中,形成了(Nd, Dy)2Fe14B相,从而减小了因热变形带来的矫顽力损失。电化学测试表明,热变形过程可提高磁体腐蚀电位和减小电流密度。变形条件800 ℃/70%时,磁体具有最佳的综合磁性能和电化学性能,其磁性能可达：Br=1.34 T,Hcj=1225 kA/m和(BH)max=286 kJ/m3。     

纳米结构稀土永磁材料的制备及表征研究进展

稀土永磁材料是迄今磁性能最强、应用最广泛的一类永磁材料。与传统的粗晶稀土永磁材料相比，纳米结构稀土永磁材料因其独特的显微组织结构而具有显著不同的磁性能，从而引发了研究者的广泛关注。全面回顾了近年来R-Co(R=Sm, Pr, Y, La)和R-Fe-B(R=Nd, Pr, Tb, Dy)体系纳米结构永磁材料的发展历程。重点介绍了用于R-Co和R-Fe-B纳米结构材料的制备方法，包括熔体快淬、高能球磨(HEBM)、表面活性剂辅助球磨(SABM)和机械化学合成等方法。还讨论了将纳米结构前驱体制备成块状磁体的先进技术，其中包括放电等离子烧结(SPS)、感应加热法(IHC)、冲击波压实(SWC)、燃烧驱动压实(CDC)、高压温压(HPWC)等方法。同时介绍了各向同性以及各向异性的纳米结构单相R-Co和R-Co/Fe纳米复合磁体的微结构特性和磁性能。讨论了各向同性和各向异性纳米结构单相R₂Fe₁₄B磁体，以及由硬磁相和软磁相组成的交换耦合纳米复合R-Fe-B/Fe(Co)磁体的磁性。     

掺杂La-Ce-Cu合金对热变形Nd-Fe-B磁体磁性能和微观结构的影响

研究采用放电等离子烧结(SPS)技术制备了掺杂不同含量的La-Ce-Cu合金的Nd-Fe-B热变形磁体;研究了掺杂量对磁体磁性能和微观结构的影响。结果表明,随着掺杂量的增加,热变形Nd-Fe-B磁体的矫顽力先增加后降低;而剩磁与磁能积均有所下降。磁体的矫顽力在掺杂量为1%(质量分数)时,达到最大值为1257kA/m。微观分析表明,掺杂合金中的La元素倾向于分布在富稀土相中,不易进入主相晶粒;而Ce元素则易取代Nd进入主相晶粒中。     

基于快淬NdFeB粉末的放电等离子烧结永磁的组织和性能

利用纳米晶快淬NdFeB粉末为原材料,采用放电等离子烧结(SPS)技术制备了高密度各向同性块体永磁.研究了放电等离子火花烧结磁体不同部位的磁性能和显微组织形貌,比较了烧结压力对磁体的组织和性能的影响.结果表明,由于组织的差异,烧结磁体不同部位磁性能略有不同,内部的剩磁较高,磁体边缘的矫顽力较高,而半径中点处的综合磁性能最好.烧结压力对烧结磁体的密度、显微组织,晶粒大小和形状以及磁性能都有重要影响.高的烧结压力有利于提高磁体密度、减小粗晶区体积、改善磁性能.SPS磁体中存在明显的晶间交换耦合作用.     

放电等离子烧结制备高性能NdFeB永磁材料

采用放电等离子烧结技术制备高性能新型NdFeB永磁材料,研究烧结工艺和热处理工艺对磁体组织性能的影响。采用扫描电子显微镜观察磁体的微观组织,利用B-H回线仪检测磁体的磁性能。结果表明:较高的烧结温度有利于磁体的致密化,但过高的温度则阻碍液相在主相晶界的浸润,从而降低磁体的致密度。在优化工艺条件下制备出具有独特的微观组织且最佳性能为Br=1.351 T,Hci=674.4 kA/m,BHm=360.4 kJ/m3的新型SPS NdFeB磁体。     

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.     

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。     

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.     

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.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.