复合变质对Al-20Si合金冲击性能的影响

在不同P、RE添加量下对P-RE复合变质和未变质的过共晶铝硅合金的冲击韧度进行了研究.结果表明,P-RE复合变质明显提高了合金的冲击韧度,当加入0.08%的P和0.6%的RE时,合金的冲击韧度达到最佳,合金的冲击韧度从未变质的9.786 2 J/cm2提高到11.009 8 J/cm2,提高了12.5%.冲击断裂机制主要是脆性断裂,也伴随有韧度断裂.合金冲击韧度的改善与复合变质引起的共晶硅和初晶硅颗粒的细化和合金强度、塑性的提高有关.     

不同水基淬火介质对ZG30CrMnSiMo低合金钢组织和耐磨性的影响

通过扫描电镜、冲击试验机和动载冲击磨料磨损试验机等对低合金耐磨钢显微组织、力学性能和耐磨性能进行了分析。结果表明:铸态组织由珠光体和碳化物组成,铸态合金的宏观硬度为41.3 HRC,冲击吸收能量为6.1 J,磨损量为1.4378 g。经水玻璃(Na₂SiO₃)和PAG淬火后,显微组织均转变为回火板条马氏体和碳化物,宏观硬度分别为49.0 HRC和51.1 HRC,冲击吸收能量分别为7.3 J和9.4 J,磨损量分别为0.9378 g和0.8350 g。相比铸态合金,PAG淬火后合金的宏观硬度、冲击性能和耐磨性分别提高了23.7%、54.1%和1.7倍。相比水玻璃淬火,PAG淬火后合金钢的宏观硬度、冲击性能和耐磨性分别提高了4.3%、28.8%和1.1 倍。     

浇注温度对ZA27合金凝固组织和冲击韧度的影响

以ZA27合金为对象,研究了不同浇注温度对其凝固组织、冲击韧度和断口形貌的影响,结果表明:500℃浇注时,试样凝固组织中α相呈发达的枝晶状,其占有率最大为35.52％,试样断口中撕裂棱短小,韧窝细小均匀分布,冲击韧度值最高为100 J/cm2;当浇注温度为450℃时,α相呈块状或破碎枝晶状,占有率为31％,断口中韧窝细小但分布不均匀,冲击韧度值为84 J/cm2;当浇注温度高于500℃时,从550～650℃的升高过程中,α相由枝晶状逐渐转变成块状,其占有率由32.68％减小到26.21％,600℃的断口中韧窝数量少尺寸大,撕裂棱具有一定方向性,冲击韧度由91 J/cm2减小到74 J/cm2；浇注温度为500℃时ZA27合金的冲击韧度最好.     

焊接热输入对X90管线钢焊接接头组织与性能的影响

通过金相试验、SEM试验、拉伸试验、冲击试验,分析不同焊接热输入下X90管线钢焊接接头的组织和力学性能。结果显示,当焊接热输入为15 k J/cm时,组织性能变化较小;焊接热输入增大至21 k J/cm时,接头焊缝区的显微组织晶粒变粗大,铁素体含量增加,板条贝氏体含量减少,对强韧性影响不大;当热输入增大至30 k J/cm时,接头HAZ冲击吸收能量KV2急剧减小51 J。在焊接热输入为21 k J/cm时,由于板条贝氏体、铁素体、M/A和分布于基体上的粒状贝氏体共同作用,使X90管线钢焊接接头具有优良的组织和力学性能。     

线能量对NM12焊丝熔敷金属道间粗晶区性能的影响

NM12是自行研制的一种新型耐磨药芯焊丝。利用Gleeble3500热模拟试验机模拟了该焊丝熔敷金属在19.5、25、39、50 k J/cm四种线能量下的道间粗晶区组织。通过冲击试验、金相观察、硬度试验和滑动磨损试验对模拟粗晶区的组织和性能进行了研究。结果显示:随着线能量的增大,模拟粗晶区的晶粒增大,析出物增多,残奥减少,组织为马氏体+碳化物+残奥;当线能量为50 k J/cm时,出现粒状贝氏体。在四种线能量下NM12焊丝熔敷金属模拟粗晶区的冲击功都很低。模拟粗晶区试样的硬度随线能量的增加而略有增加,耐磨性能随着线能量的增加先提高后小幅降低,线能量为25 k J/cm时磨损量最小。研究认为,线能量对NM12焊丝熔敷金属模拟粗晶区性能的影响不大,该焊丝可应用于双丝埋弧焊的大线能量下。     

Q460NH耐候钢在不同焊接热输入条件下的冲击性能及显微组织变化

为研究不同焊接输入条件对海面建筑用Q460NH钢的冲击性能的影响,分别在不同热输入条件下对Q460NH钢进行焊接,并在-30℃低温对Q460NH钢的冲击功和显微组织进行测试和观察。结果表明:当热输入为21 k J/cm时,Q460NH钢的冲击功达到最大值84 J;当热输入大于21 k J/cm时,Q460NH钢的冲击功呈现下降趋势。针状铁素体的面积分数随着热输入的增加呈先增加后减小的趋势,而侧板条铁素体和晶界铁素体的面积分数随热输入的增加呈先减小后增加的趋势。     

热输入对Q550D高强钢热影响区组织和性能的影响

对工程机械用Q550D钢进行不同热输入的焊接热模拟试验,研究其金相组织、硬度、冲击性能和冲击断口形貌。结果表明,模拟的粗晶区主要组织为板条贝氏体,当线能量超过20 kJ/cm时组织中还出现了少量粒状贝氏体。随着热输入的提高,原始奥氏体晶粒和贝氏体板条逐渐粗化;粗晶区的平均硬度值逐渐降低,当线能量为15 kJ/cm时粗晶区明显硬化,而当线能量达到30 kJ/cm时软化;冲击功逐渐降低,特别是当线能量超过20 J/cm时模拟的粗晶区冲击韧性严重恶化。     

医用NiTi合金在Hank's模拟体液中的微磨损行为

目的 研究医用NiTi合金在Hank’s模拟人体生理溶液中的微磨损行为。方法 采用TE66微磨粒磨损试验机对医用NiTi合金进行微磨损测试,计算合金磨损率,采用SEM观察合金磨损后的表面形貌来分析磨损机制。在测试过程中考虑加载载荷、磨损颗粒浓度、磨损颗粒类型及尺寸对合金微磨损行为的影响。结果 NiTi合金的磨损率随载荷的增加而降低。当载荷小于1.0 N时,合金的磨损率受磨损颗粒浓度的影响不大;当载荷大于1.0 N时,合金的磨损率随磨损颗粒浓度的增加而增加。在同一尺寸下,由于SiC颗粒具有较高的硬度和较大的切削力,所导致的NiTi合金的磨损率比Al2O3颗粒造成的磨损率要大。当磨损颗粒为SiC时,NiTi合金的磨损率随磨损颗粒尺寸的变化无明显规律性。在所涉实验条件下,当磨损颗粒为SiC F1200,摩擦配偶为ZrO2,加载载荷为2.0 N,磨损颗粒质量浓度为0.05 g/cm3时,所获得NiTi合金的磨损率最低,为2.3×10?5 mm3/(N?m)。结论 在同一磨损颗粒浓度下,合金的磨损率随加载载荷的增加而降低。在较低载荷时,磨损颗粒的浓度对合金的磨损率影响不大;在较高载荷下,随磨损颗粒浓度的增加,合金的磨损率增加。磨损机制以磨粒磨损为主。     

钒加入量对稀土低铬铸铁组织和性能的影响

采用测试硬度、冲击韧度和观察显微组织等方法,研究了钒加入量对稀土低铬合金铸铁组织和性能的影响。研究表明:在铸态条件下,随着钒含量的增加硬度增大,当钒含量到达1%时,其硬度达到53.6 HRC;经过250℃回火保温2 h的热处理后,试样的硬度呈先增加后降低的趋势,钒含量为0.75%时,硬度达到55.5 HRC。铸态条件下,当钒含量为0.75%时,冲击韧度达到5.8 J/cm2。经过同样的热处理工艺后,试样的冲击韧度有较大程度地提高,当钒含量为0.75%时达到10.7 J/cm2。通过对试样的金相组织观察发现,随着钒含量的增加,网状碳化物数量减少,热处理后局部出现断网,有白色碳化物析出。     

热处理工艺及合金化对ZG30的硬度及冲击韧度的影响

试验在ZG30中添加了适当的Cr、Mo合金进行强化,并用稀土变质处理,研究了热处理工艺对其性能的影响,分析了不同热处理工艺条件下该合金的力学性能。结果表明,当Cr、Mo加入量分别w为0.8%~1.2%、0.3%~0.5%,稀土变质剂加入的量w为0.03%~0.06%时,经过等温淬火和低温回火后,合金硬度可达到44.5 HRC,冲击韧度为38.9 J/cm2。经过合金化并经过相应的热处理的ZG30作为一种捣镐材料,可以满足捣镐的性能要求。     

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.     

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.