超细晶硬质合金显微组织参数与力学性能定量关系的研究

对超细晶WC-Co硬质合金的复相显微组织进行了系统的定量化表征和分析,获得了WC晶粒尺寸d_(WC),Co相平均自由程L_(Co)和WC晶粒邻接度C_(WC-WC)等显微组织参数与力学性能的定量关系,模型预测结果与实验测定结果符合很好.结果表明,当C_(WC-WC)基本相同时,超细晶硬质合金的硬度分别与d_(WC)~(-1/2)和L_(Co)~(-1/2)成线性正比关系,断裂韧性K_(IC)分别与d_(WC)~(-1/2)和L_(Co)~(-1/2)成确定性函数关系.在Co含量一定、WC平均晶粒尺寸基本相同的情况下,随着C_(WC-WC)的增大,超细晶硬质合金的横向断裂强度降低,且当C_(WC-WC)>0.5时,硬质合金的强度随C_(WC-WC)增加显著下降.     

含WB烧结硬质合金的组织结构和性能研究

将不同含量的WB粉末添加到传统成分的WC-Co粉末中,利用低压烧结技术制备了系列含WB的WC-Co型硬质合金,并对其物相组成、组织结构和力学性能进行了系统表征分析。研究发现,在低压烧结过程中WB与Co发生反应,生成了具有超高硬度的WCoB相,由此降低了粘结相Co对WC晶粒的隔离,增加了WC晶粒间的接触度,引起合金韧性下降。添加WB制备的硬质合金材料其摩擦系数更低,随WB添加量的增加,硬度和耐磨性明显提高,当WB添加量为30%(质量分数)时,制备的硬质合金材料的硬度达到19 000 MPa,其磨损速率仅为传统WC-Co硬质合金1/10。然而,添加WB的WC-Co合金的断裂韧性约为传统WC-Co硬质合金的83%~91%。     

应力比对WC-Co硬质合金疲劳寿命及裂纹生长行为的影响(英文)

通过两种疲劳试验:旋转弯曲疲劳试验和3-或4-点弯曲疲劳试验测试细晶WC-Co硬质合金的裂纹生长行为和疲劳寿命。疲劳试验结果表明:所测试的大部分WC-Co硬质合金的疲劳寿命取决于裂纹生长周期。利用断裂力学基本方程推导出疲劳裂纹生长速率(da/dN)和最大应力强度因子(Kmax)的关系。根据此关系,获得材料的强度因子阈值(Kth)和疲劳断裂韧性值(Kfc)。基于修正的线性弹性断裂力学方程,对WC-Co硬质合金材料的疲劳寿命进行计算,疲劳寿命的计算结果与实验结果吻合较好。     

钴含量及晶粒度对硬质合金冲击疲劳性能的影响

采用冲击弯曲试验研究了硬质合金的冲击疲劳性能。结果表明,当晶粒度一定时,硬质合金的冲击疲劳性能随着钴含量的增加而提高;当钴含量一定,WC晶粒度为1.2～3.2μm时,WC-Co硬质合金的冲击疲劳性能先是随着WC晶粒度的增粗而提高,当晶粒度增加到一定程度时,冲击疲劳性能出现下降。超细晶粒硬质合金的冲击疲劳性能明显高于一般WC-Co硬质合金。     

化学镀法制备低钴含量WC-Co复合粉体及其放电等离子烧结

对WC粉体进行化学活化预处理,然后采用超声辅助化学镀法制备低钴含量WC-Co(≤1 mass%)复合粉体,采用放电等离子烧结(SPS)技术,制备了少粘结相WC-Co硬质合金材料。研究了化学活化预处理工艺对WC粉体表面化学镀Co的影响以及少量均匀包覆的Co对试样烧结致密化过程、显微组织结构及力学性能的影响。试验结果表明:化学活化预处理后的WC粉体出现了大量的层错、位错等缺陷,在缺陷周围产生点阵畸变和应力场,较大的表面能减小了金属与陶瓷界面接触角,提高了二者之间的润湿性,降低了化学镀过程的形核功,实现化学镀钴过程;与纯WC粉体烧结试样相比,少量Co在WC-Co复合粉体中的均匀分布,大大降低了烧结温度,促进了粉体烧结致密化进程,各项性能得到显著提高,密度达15.56 g/cm3,硬度为2409 HV30,断裂韧性为9.2 MPa.m1/2。     

淬火温度对ZL40.5硬质合金微观组织结构的影响

传统硬质合金中硬度和韧性是难以兼得的一对矛盾体,而通过热处理改善WC-Co硬质合金结构与性能则可获得具有优异综合性能的硬质合金。本文以压制烧结制成的ZL40.5硬质合金为研究对象,在1 050～1 300℃范围内进行油性介质淬火,采用扫描电镜(SEM)及X射线衍射(XRD)等检测方法研究了淬火温度对ZL40.5硬质合金微观组织结构的影响。结果表明:淬火过程中WC晶粒尖角溶解,形貌变得圆钝;随淬火温度升高,Co相体积分数升高,WC晶粒尺寸、邻接度略有降低;W、C原子在Co中的固溶度随淬火温度增加而增加,进而使室温下保留的α-Co含量随之增加,淬火温度在1 250℃时具有最佳结构参数。     

基体特性对TiSiN/TiAlSiN/AlTiN涂层WC-Co硬质合金膜基结合力的影响

基体物相特性会对涂层硬质合金整体的力学性能产生重要影响。制备了具有不同WC晶粒度和Co含量的WC-Co系列硬质合金,采用直流磁控溅射技术在其表面沉积同种Ti_(0.94)Si_(0.06)N/Ti Al Si N/Al_(0.52)Ti_(0.48)N涂层。结果表明,随WC-Co硬质合金基体WC晶粒度(1.2～0.4μm)的降低或Co含量(12Co～3Co)的减少,涂层与基体完全剥离时的临界载荷L_(C2)逐渐增大。L_(C2)与基体硬度H_S或弹性模量E_S之间在数值上具有较好的线性正相关性。涂层首次剥离时的临界载荷L_(C1)能反映涂层的内聚失效抗力。适当的WC晶粒度和Co含量(超细晶10Co)能避免涂层产生较早的内聚失效或界面失效,有利于L_(C1)和L_(C2)的同步改善。     

WC-Co硬质合金结构参数对烧结表面残余应力的影响

通过建模分析和实际测量,对WC-Co硬质合金结构参数与烧结表面残余应力之间的关系进行了研究。结果表明,硬质合金的结构参数对烧结表面残余应力有很大的影响。相同WC粒径条件下,随Co相体积分数的增大,硬质合金烧结表面残余应力的数值增大。当Co相体积分数固定时,增大WC颗粒的粒径,可明显降低硬质合金烧结表面的残余应力。实际测量结果与分析结论相吻合。     

功能梯度WC-Co/WC-Fe-Ni双层硬质合金的研究（英文）

使用新的制备方法成功制备了功能梯度WC-Co/WC-Fe-Ni双层结构硬质合金。冷压成型所需的压制压力需要保持在15MPa,在这个压力下WC-Co和WC-Fe-Ni层的烧结收缩率相同,制备的双层合金没有分层和裂纹等不利现象出现。采用X射线衍射(XRD)仪、光学显微镜(OM)和扫描电子显微镜(SEM)等实验手段研究了双层合金的相组成与微观结构。发现合金中没有η或者石墨相的存在,而且,WC-Co和WC-Fe-Ni层间的界面处结合良好。同时,在WC-Co/WC-Fe-Ni双层结构硬质合金的界面处有明显的连续变化的Fe,Ni和Co成分梯度,两层间的成分梯度导致界面附近的硬度梯度的形成。制备的功能梯度WC-Co/WC-Fe-Ni双层结构硬质合金同时具有高的硬度、耐磨性和韧性。     

WC-Co-(Ni)-(Cr)硬质合金在中性溶液中的腐蚀行为

以WC粉、Co粉、Ni粉及Cr3C2粉为原料,采用粉末冶金方法制备了3组不同粘结相成分的WC-Co-(Ni)-(Cr)硬质合金,通过极化曲线测试和浸泡实验研究了3组合金在中性溶液中的腐蚀行为,并采用扫描电镜、能谱分析、X射线光电子能谱(XPS)和EBSD等手段对其腐蚀机理进行了探讨。结果表明,WC-Co和WC-Co-Cr硬质合金在中性溶液中主要发生粘结相Co的腐蚀,浸泡产生的腐蚀产物主要是Co(OH)2;添加Cr将提高WC-Co硬质合金在中性溶液中的耐腐蚀性能,这可能与Cr的添加明显降低了粘结相中密排六方Co的含量有关;同时添加Ni和Cr可进一步提高WC-Co合金在中性溶液中的耐腐蚀性能,在pH=7的Na2SO4溶液中浸泡480 h后,WC-Co-Ni-Cr合金发生很少量的腐蚀。     

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.     

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.