工业纯铜渗硅层冲蚀磨损性研究

以SiO₂为渗剂,对工业纯铜进行粉末渗硅。渗硅层有Cu_0.83Si_0.17等新相产生,渗层的显微硬度最高达到349 HV0.05,约为基体的5.1倍。冲蚀磨损性能测试表明,随转速增加、冲蚀液水砂比增加,试样的磨损量均增加,渗硅试样比纯铜试样的耐冲蚀磨损性能有明显提高。抗冲蚀磨损性可提高3.02~3.69倍。同样,在人工配制的海水环境中,渗硅试样也表现出良好的耐冲蚀性能。     

GH738合金表面Al-Si渗层的制备及其抗氧化行为

采用热扩散法在GH738合金表面制备出Al-Si渗层。通过X射线衍射仪(XRD),扫描电镜(SEM),能谱仪(EDS)分析了Al-Si渗层形貌、厚度、物相组成和元素分布;采用显微维氏硬度计测定了渗层的硬度;采用静态增量试验方法,在1200℃,对Al-Si渗层试样和GH738镍基合金基体进行了100 h的恒温抗氧化性能测试。结果表明,Al-Si渗层厚度可达120μm,渗层为明显的双层结构,外层为Al-Si层,内层为互扩散层;渗层物相组成主要为NiAl和Ni₂Al₃以及少量Cr₃Si;渗层表面硬度达到900 HV0.1左右,约为基体的3.5倍;Al-Si渗层氧化动力学曲线满足抛物线规律,氧化速率常数为0.0987 mg²·cm^-4·h^-1,表面形成比较致密的Al₂O₃保护膜,其高温抗氧化性能较基体提高了约5倍。     

工业纯铜渗铝层的热处理工艺

首先采用粉末包埋法对工业纯铜进行渗铝,为进一步提高渗铝层强化效果,采用固溶处理、时效、深冷处理等多种工艺对工业纯铜渗铝层进行热处理。对热处理后的渗层的组织结构、硬度、耐磨性、耐蚀性及抗氧化性进行了研究。研究结果表明,渗铝层为α+(α+γ_2)组织。固溶水冷后,获得类似马氏体的针状组织β',深冷处理后,获得具有一定脱溶析出的细小β'组织,β'在300℃时效处理时发生脱溶,析出大量弥散析出相。经各种热处理后,硬度、耐磨性、耐蚀性及抗氧化性均有所提高。其中,固溶加热后直接液氮冷却+时效处理后,硬度达145.9 HRF;时效处理后大量弥第二相析出,有利提高耐磨性;渗层耐蚀性较纯铜提高一个数量级;热处理后组织更为细小致密,有效抑制表面氧化,表现出更好的抗氧化性。本研究采用的复合热处理工艺使纯铜渗铝层使用性能大幅提高,具有十分重要的实际应用价值。     

氩弧重熔Q235钢B-C-N共渗层的组织结构及耐磨性

采用粉末包埋法对Q235钢进行B-C-N共渗,并对共渗层进行氩弧重熔。观察共渗层和熔覆层的显微组织并进行结构分析,测试共渗层及熔覆层的显微硬度和耐磨性。结果表明：共渗层的显微组织由FeB、Fe₂B、Fe₃B、Fe₂N、Fe₈N和Fe₃C相组成,氩弧重熔层形成了新相Fe₂₃(B, C)₆和Fe₃N等;共渗层显微硬度最高值为1198.4 HV0.1,重熔层的最高硬度值为1192.8 HV0.1,但硬度梯度变化平缓;共渗层、氩弧重熔层相对基体的耐磨粒磨损性能分别为2.77、3.76倍;共渗层、氩弧重熔层相对基体的耐粘着磨损性能分别为1.95、3.23倍,摩擦因数分别为0.502、0.462,较基体均有所下降。     

0Cr18Ni9Ti不锈钢表面渗锆改性层的低温预氧化行为

对不锈钢基材、经渗锆处理及渗碳处理后的试样,在620 ℃静态空气中低温预氧化6 h的氧化行为进行研究。结果表明：预氧化后,不锈钢基材表面主要形成FeCr_0.29Ni_0.16C_0.06、Fe_0.64Ni_0.36、Fe₂O₃,出现较多深而宽的裂纹;渗Zr试样低温预氧化后表面主要为Fe₂O₃、ZrO₂,试样表面致密、没有出现大的裂纹;渗Zr+渗C试样,低温预氧化后表面生成物主要为ZrO₂,较渗Zr后更为致密,表面光滑且无孔洞与裂纹,基体与改性层结合牢固,抗高温氧化性能大为改善,试样表面的硬度约为2580 HV0.05,且由表及里试样硬度值呈梯度降低平缓。     

热处理对Al2O3f/Mg-6Al-0.5Nd-0.5Gd复合材料组织及硬度的影响

采用金相显微镜、维氏硬度测试仪及扫描电镜等,研究热处理工艺对Al₂O_3f /Mg-6Al-0.5Nd-0.5Gd复合材料微观组织及硬度的影响。结果表明,固溶处理后β-Mg_l7A1₁₂相大部分固溶于α-Mg基体中,而稀土化合物Al₂Nd、Al₂Gd相因其高熔点,在试验温度下不能分解与固溶,Al₂O_3f纤维变得细小均匀,Mg₂Si相呈一定的分解、球化趋势。时效处理使β-Mg_l7A1₁₂相再次析出,呈层片状或弥散颗粒状分布,优化了其铸态时粗大的网状结构,此时,复合材料硬度达到最大值,比铸态时提高了47.5%。     

TC4合金表面扩散渗硅涂层的高温氧化行为和失效机制

为提高钛合金的高温抗氧化性能,采用固体粉末扩散渗方法在其表面制备了扩散渗硅涂层,研究了涂层的组织结构、高温氧化行为和失效机制。结果表明,所制备涂层具有致密的多层梯度组织结构,主要由TiSi₂外层,TiSi中间层和Ti₅Si₄+Ti₅Si₃内层组成。高温氧化实验结果表明,涂层在850℃空气中氧化时表面形成了由SiO₂和TiO₂混合组成的保护膜,高温抗氧化性能优良;氧化过程中,涂层与基体合金中Si和Ti的互扩散引起氧化膜内TiO₂含量增加及Si源不足,导致氧化膜保护性变差;氧化产物与涂层之间较高的P-B比、氧化膜与涂层组织间热膨胀系数不匹配导致了氧化膜开裂和剥落。     

汽车用AZ31镁合金激光熔覆Al-Si涂层的组织与性能

通过激光熔覆Al-Si涂层的方法对AZ31镁合金表面进行了改性,研究了熔覆层的物相组成、显微组织、显微硬度、耐磨性和耐腐蚀性能。结果表明,熔覆层主要由Mg₂Si、Mg₁₇Al₁₂、Al₃Mg₂、Al₂Mg相组成,与基体呈冶金结合,硬度最高达到152 HV;耐磨性和耐腐蚀性较好,磨损失重及腐蚀速率分别为基体的1.75倍和1.88倍。     

纯镍渗硼硅处理工艺及组织性能研究

采用粒状渗剂分别在渗硼硅温度为850、900、950℃,保温时间为2、8 h的工艺参数下对纯镍表面进行固体渗硼硅处理。用光学显微镜(OM)对渗层横断面进行了显微组织观察,用显微硬度计测试渗层的硬度分布,用M200型磨损试验机研究未渗硼硅和渗硼硅纯镍的耐磨性,采用循环氧化试验研究未渗硼硅和渗硼硅纯镍的抗高温氧化性。结果表明,纯镍渗硼硅后,渗层为硅化物层和硼化物层,且硅化物和硼化物的显微硬度都大于基体硬度,渗层厚度随着渗硼硅时间和温度的增加而增加,其范围约为36~237?m,用X射线衍射仪(XRD)分析出渗层为硼化物层(Ni2B)和硅化物层(Ni3Si、Ni5Si2和Ni2Si)。磨损试验结果表明渗硼硅后试样的耐磨性得到提高。抗高温氧化试验结果显示未渗硼硅纯镍试样抗高温氧化性优于渗硼硅后纯镍试样。     

铜在SiH4／H2混合气氛中获得的渗硅层的抗氧化性能

研究了用硅烷－氢（ＳｉＨ４／Ｈ２）混合气体在铜表面获得的渗硅层的抗氧化性，结果表明，纯铜表面渗硅层的形成提高了材料的抗高温氧化性能。本文对渗硅层的氧化机理进行了探讨。     

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.     

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。     

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.     

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.     

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).     

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.