H13锻材球化退火工艺试验研究

在试验室采用箱式电阻炉,对H13锻材料段进行球化退火工艺试验。试验结果表明,H13锻材经830℃低温球化退火处理后,显微组织粗大,偏析严重,球化不完全,大部分碳化物呈网状结构;经1050℃超细化处理+830℃低温球化退火后,H13钢组织细化,合金元素偏析得到改善,减轻了带状偏析,获得了均匀细小的球化组织。     

消除H13钢锻后组织中链状碳化物的热处理工艺研究

分析了H13钢退火组织中链状碳化物的分布特点,对H13钢进行不同工艺的固溶处理+球化等温退火,研究了固溶处理对H13钢链状碳化物的溶解情况及退火组织均匀性的影响。研究表明,固溶处理可明显改善H13钢退火组织中的碳化物偏析,消除链状碳化物,提高碳化物的球化率及分布均匀性。在一定温度范围内,随固溶温度升高,退火组织越均匀。经1050℃固溶处理后,H13钢退火组织达到NADCA#207-2003标准中的AS6级,球化效果良好,获得了碳化物弥散均匀的粒状珠光体组织。     

高温均匀化退火及淬火介质对H13钢组织和力学性能的影响

对H13钢进行了锻前高温均匀化退化和锻后热处理淬火介质研究,对其显微组织和力学性能分析。结果显示,H13钢经高温均匀化退火碳化物减少,带状偏析情况得到改善,组织均匀化,冲击韧性提高;淬火试验中采用了PAG淬火液和淬火油不同的淬火介质,经PAG淬火后硬度较油淬更高,综合性能相对较好。     

均匀化退火对32Cr2Mo2NiVNb钢组织和性能的影响

采用光学显微镜、扫描电镜分析技术,并结合力学性能测试,研究了32Cr2Mo2NiVNb钢在1100 ℃均匀化退火不同时间(0～8 h)对其组织和力学性能的影响.结果表明,均匀化退火可明显改善材料带状偏析,同时可较大幅度提高材料的横向冲击韧性.经1100 ℃×8 h均匀化退火后,材料带状组织基本消除,横向冲击韧性由42 J/cm 2提高到60 J/cm 2.     

改善H13系列热作模具扁钢退火组织的工艺研究

高端H13系列扁钢的退火组织应满足北美压铸协会标准《NADCA#207》或热作工具钢显微检验标准?SEP1614?的要求,某公司H13系列扁钢退火组织一次合格率仅为79%,通过调整钢锭的高温扩散工艺、增大扁钢轧后在线冷却强度及延长等温球化退火保温时间等工艺措施成功改善了带状偏析、液析碳化物、退火组织均匀性等问题,一次合格率提升至98%以上。     

两种国内外铝挤模具材料组织和力学性能研究

利用金相显微镜和冲击试验机等研究了两种国内外铝挤模具材料组织和力学性能,对抚顺特钢生产的1.2344钢和ASSAB的8407 2M钢,进行了化学成分、带状偏析、退火组织和冲击韧性对比分析。结果表明:抚顺特钢1.2344钢氧含量和氮含量均高于8407 2M钢,钢材横向截面边部带状偏析优于8407 2M钢,1.2344钢退火组织中存在少量网状碳化物,冲击边部较低与8407 2M钢差距较大。     

高温正火对H13钢锻后组织的影响

对H13热作模具钢高温正火+球化退火处理,研究了高温正火对H13钢锻后组织的影响。结果表明,高温正火能改善H13钢锻后组织,减少组织偏析和网状碳化物。在一定时间范围内,随正火保温时间的延长,组织改善越显著。H13钢锻后经Ms点以上空冷,再经高温正火,得到球化组织更均匀弥散,球化效果更好。     

两种热作模具H13钢组织和性能研究

利用金相显微镜和冲击试验机等研究了两种国内外高级优质热作模具H13钢组织和力学性能。结果表明:抚顺特钢生产的H13钢和瑞典一胜百的8407钢,对化学成分、带状偏析、退火组织和冲击韧性进行对比分析。抚顺特钢生产的H13钢化学成分P含量低于瑞典一胜百8407钢,8407钢带状偏析略优,抚顺特钢H13钢退火组织心部可见少量网状碳化物,冲击边部略优于8407钢。     

预处理工艺对热作模具钢5Cr8MoNi2SiV组织与硬度的影响

研究了一种新型热作模具钢5Cr8Mo Ni2Si V的热力学相变规律和CCT曲线,为改善该钢铸态组织的严重偏析和提高材料切削性能,分析普通常规退火、正火+球化退火和正火+等温球化退火3种预处理工艺对该钢组织和性能的影响。结果表明:试验钢经1090℃×1 h正火+880℃×2 h+680℃×48 h等温球化预处理,能显著改善碳化物偏析,并使硬度大大降低,改善切削性能。     

保护气氛电渣重熔H13模具钢组织和性能研究

邢台钢铁有限责任公司利用具有保护气氛的抽锭式电渣炉生产Ф600 mm的H13钢锭,并锻造成不同规格的模块。研究了熔速对铸态组织的影响以及锻造工艺对H13钢显微组织和冲击性能的影响。结果表明:在400~550 kg·h-1熔速范围内,钢锭铸态组织中都存在不同程度的枝晶间显微偏析,并有液析碳化物析出。熔速为500 kg·h-1时,铸态组织显微偏析较轻,液析碳化物尺寸较小,且数量较少。在500 kg·h-1熔速下生产的钢锭经不同的锻造工艺变形后发现,只进行单向拔长变形的组织中存在明显的带状偏析,枝晶未被打碎,仍保留了铸态的针状铁素体组织;一镦一拔变形后的组织,铁素体位向逐渐趋于等轴状,碳化物均匀分布程度有提高,但晶界上仍有呈链状析出的碳化物,带状组织未完全消除;三镦三拔多方向反复变形后,枝晶被充分打碎,带状偏析消除,锻后退火组织中的粒状珠光体和碳化物细小均匀,横向冲击韧性明显提高,达到15.5 J·cm-2。     

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.