热处理对一种新型耐磨铸钢组织与性能的影响

对一种新型耐磨铸钢进行了不同温度的淬火和回火处理。淬火温度分别为850、880和910℃,回火温度分别为200、250和300℃。利用金相显微镜(OM)和扫描电子显微镜(SEM)观察并分析了试验钢热处理后的显微组织,同时测试了试验钢的洛氏硬度、显微硬度、耐磨性能和拉伸性能。结果表明:经不同温度淬火后,试验钢的组织均为板条马氏体;随着淬火温度的升高,试验钢的硬度先升高后降低,880℃淬火的钢硬度最高。经880℃淬火、不同温度回火的试验钢的组织均为回火马氏体;随着回火温度的升高,试验钢的硬度先增加后减小,抗拉强度逐渐升高,磨损量先减小后增加。经880℃淬火、250℃回火的试验钢的综合力学性能最佳。     

42CrMoVNb钢的热处理工艺优化及力学性能

利用单因素和正交试验对42CrMoVNb钢的热处理工艺进行了优化,利用洛氏硬度计、万能拉伸试验机和金属摆锤冲击试验机检测了相关的力学性能,研究了热处理工艺对42CrMoVNb钢组织和力学性能的影响。结果表明,42CrMoVNb钢的最优淬火回火工艺为860℃×20 min,油冷+440℃×150 min,空冷;经最优工艺处理后其组织为回火屈氏体基体上弥散分布着细小的碳化物颗粒,硬度、抗拉强度、屈服强度、屈强比、断后伸长率、断面收缩率和-20℃低温冲击吸收能量分别为44.5 HRC、1467 MPa、1357 MPa、0.93、10.5%、46%和27.1 J;力学性能满足14.9级高强度螺栓的技术指标要求。     

热处理工艺对新型C级矿用圆环链用钢组织与性能的影响

通过同一种钢在不同淬火条件(20及37℃水淬)下的试验比较,研究了淬火温度对回火后钢性能的影响.对试验钢分别进行淬火温度为880、940℃的一系列淬火试验及回火试验.结果发现,不同淬火温度及在20℃水淬条件下,φ26mm的试验钢均可淬透;当水温为37℃时经400℃回火,可获得良好的综合力学性能.     

42CrMo钢的等温淬火和回火

通过在Ms点上下温度范围等温淬火处理和改变回火温度,研究了等温淬火温度、时间,回火温度对42CrMo钢显微组织、硬度和冲击韧度的影响。结果表明,42CrMo钢经260 ℃等温15 min可获得马氏体+(10%～15%)的下贝氏体,并具有最高的硬度和较高的冲击韧度。随着等温淬火温度提高和时间的延长,下贝氏体量逐渐增加,且硬度也逐渐降低,但冲击韧度则在等温45 min时达到最大值。42CrMo钢经等温淬火后,随着回火温度的增加,碳化物不断析出聚集,使得硬度逐渐降低,同时这也导致了42CrMo钢等温淬火后组织在360 ℃回火时存在显著的回火脆性,冲击韧度急剧下降。     

淬火回火对ZG310-510铸钢组织和力学性能的影响

研究了淬火温度和回火温度对ZG310-510铸钢组织和力学性能的影响.结果表明,随着淬火温度的提高,ZG310-510钢的强度、硬度和冲击韧度提高,淬火温度为1000℃达到峰值.1000℃淬火、200或600℃回火,铸钢具有良好的强韧性,200℃回火的组织为回火马氏体组织和少量残余奥氏体,600℃回火的组织主要为索氏体组织.400℃回火出现回火脆性,材料的冲击韧度最低.提出了提高ZG310-510铸钢的强韧性的热处理工艺:1000℃淬火 200/600℃回火.     

淬火与回火工艺对42CrMo钢显微组织和奥氏体晶粒长大规律的影响

研究了860～940℃淬火与200～600℃回火对42CrMo钢显微组织的影响,并用金相截线法对奥氏体晶粒尺寸进行测量,建立了42CrMo钢奥氏体晶粒生长动力学方程。结果表明,随着淬火温度和保温时间的增加,42CrMo钢中残留碳化物数量明显减少,碳化物由片状逐渐变为颗粒状。随着淬火温度的升高,板条马氏体组织变得越来越均匀细小。随着回火温度的升高,钢的显微组织向回火屈氏体、回火索氏体转变,当回火温度为600℃时,得到的回火索氏体组织更均匀密集。基于Beck模型的42CrMo钢奥氏体晶粒生长规律的拟合结果,得出奥氏体晶粒长大激活能为2.62×10³ J·mol^-1。     

淬、回火温度对含铈H13钢组织及硬度的影响

不同含量稀土Ce的H13钢在不同温度淬火30 min后空冷，不同温度二次回火2 h后空冷，进行组织观察和硬度测试。研究表明，淬火温度达到1040℃,基体组织和晶界处的碳化物减少，板条马氏体更清晰，回火温度在580℃时，显微组织为回火马氏体+回火托氏体，回火温度超过600℃,碳化物聚集长大，故最佳热处理工艺为1040℃淬火+580℃二次回火；稀土Ce含量为0.026%时，试验钢的晶粒最为细小，组织最为均匀，硬度最高，淬火硬度为650.6 HV30,回火硬度为391.4 HV30。     

热处理工艺对CM2高速钢组织性能的影响

对CW6Mo5Cr4V2(CM2)高速钢进行了不同温度的淬火和回火处理。检测了热处理后CM2钢的硬度、冲击韧性和耐磨性能。结果表明,经1 150～1 250℃淬火并于550℃回火的CM2钢的硬度随淬火温度的升高先升高后下降。1 200℃淬火、550℃3次回火的CM2钢的硬度高达65. 4 HRC,且耐磨性与冲击韧性优异。CM2钢的磨损机制为粘着磨损、氧化磨损和磨粒磨损并存。     

淬火和回火温度对W4Mo2Cr4VNb高速钢组织和力学性能的影响

研究了淬火、回火温度对W4Mo2Cr4VNb钢组织和力学性能的影响.结果表明,随着淬火温度提高,试验钢奥氏体晶粒长大较快;淬火温度从1160 ℃提高到1200 ℃,高温回火后钢的二次硬化能力明显地提高了,但韧性急剧降低;试验钢在560 ℃左右回火时出现二次硬化峰;经1160 ℃淬火,580 ℃回火后试验钢韧性和抗弯强度较好;经1200 ℃淬火、560～580 ℃回火后,红硬性良好.     

淬火工艺对低合金耐磨钢组织与力学性能的影响

选用不含Nb钢和含Nb(质量分数,0.021%)钢作为试验材料,采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、布氏硬度测试、冲击和拉伸等试验手段研究试验钢轧制后在不同温度加热淬火+回火及850℃在线淬火+不同温度回火两种热处理工艺下的组织和综合性能。结果表明:再加热淬火+回火工艺下,含Nb钢随淬火温度的提高,强度和韧性都有所提高,在950℃淬火+200℃回火处理下综合性能最佳,其强度为1843 MPa,硬度值为567 HBW,-20℃下的冲击吸收能量为31 J,符合NM500的标准;在线淬火+回火工艺下随着回火温度的提高,试验钢的综合性能降低,但含Nb钢的性能都高于相同条件下的不含Nb钢。含Nb钢在850℃在线淬火+200℃回火处理下综合性能最佳,其强度为1818 MPa,硬度值为562 HBW,-20℃下的冲击吸收能量为30 J,同样达到了NM500的标准。     

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.