纤维状硅灰石对消失模涂料性能的影响

通过测试消失模涂料的工艺性能和工作性能,研究了纤维状硅灰石对消失模涂料性能的影响规律,结果表明纤维状硅灰石能改善消失模涂料的悬浮性、触变性和涂挂性等工艺性能以及提高涂料的烘干抗裂性、常温与高温抗弯强度和常温与高温透气性等工作性能。     

消失模铸钢水基涂料粘结剂与悬浮剂的试验研究

采用抗弯强度表征涂料的强度,应用单因素试验方法研究了不同粘结剂和悬浮剂对消失模铸钢水基涂料强度和悬浮性的影响。结果表明,随着不同粘结剂含量的增加,涂料抗弯强度都有增大的趋势,各粘结剂含量相同的情况下,马铃薯改性淀粉作为粘结剂时其抗弯强度显著大于乳胶粉和糊精粘结剂,因此,选用马铃薯改性淀粉作为消失模铸钢水基涂料的粘结剂,含量1.5%~2.0%。随着不同悬浮剂含量的增加,涂料悬浮性都有增大的趋势。含量相同的Ca基膨润土和Na基膨润土,涂料的悬浮性差别不大。含量小于2.5%时,HCE对涂料悬浮性的影响优于CMC;含量大于2.5%时,HCE和CMC对涂料悬浮性的影响没有差别。考虑成本因素,选择Ca基膨润土和CMC作为复合悬浮剂,Ca基膨润土含量2.5%~3.5%,CMC含量1.5%~2.0%,所配制涂料综合性能优良,能够满足实际生产需要。     

消失模铸造涂料的应用与研究

在消失模铸造中消失模涂料的作用至关重要.结合生产实践,探讨了以石英粉为主要耐火骨料的消失模涂料的组成,对石英粉粒度的选择进行了多次试验,分析了涂料透气性、触变性、强度和悬浮性的影响因素,并阐述了混制设备对消失模涂料性能的影响.     

马铃薯改性淀粉用作消失模涂料添加剂的研究

通过单因素试验,将马铃薯改性淀粉含量设定为五个梯度,研究了马铃薯改性淀粉作为添加剂对消失模涂料工艺性能的影响.严格按照消失模涂料的配置工艺,测试了悬浮性、触变性、常温抗弯强度.实验数据表明,马铃薯改性淀粉是一种优良的粘结剂,而且能提高涂料的悬浮性和触变性.     

消失模铸造用涂料的研究

设计了消失模涂料透气性、强度的测试方法,测定了填料粒度、粘结剂种类和加入量,以及添加剂以涂料强度、透气性、浮性等工艺性能邮三缸铝合金进撖这消失模铸造涂料,进行了不同工艺的浇注试验;结果表明所配制的涂料抗弯强度不低于１．５ＭＰａ,悬浮性２４ｈ不低于９８％,透气性适中,添料保性能好,铸件未因涂料出现缺陷,浇注后易清理。     

消失模用涂料

研究消失模涂料应具备的性能，并讨论涂料性能与流变性的关系。所研制的铸钢和铸铁消失模涂料已用于生产。     

不同耐火填料对消失模铸造涂料性能的影响

研究了三种不同耐火填料对涂料性能的影响,并分别对三种涂料的悬浮性、透气性、流变性和触变性进行测定分析和比较,结果表明:耐火填料的粒度和密度是消失模涂料悬浮性和透气性的主要影响因素,涂料粒度的组成是影响流变性的主要因素.     

黄原胶对消失模铸造涂料性能的影响

为提高消失模铸造水基涂料的质量,探讨了黄原胶作为微量添加剂对涂料性能的影响.试验研究表明,铸造涂料中加入适量的黄原胶可提高悬浮性、显著增大涂料粘度和涂挂性、改善涂料的流变行为.黄原胶还可显著提高涂层的强度,但使涂层透气性略有降低.鉴于黄原胶的优异性能,可望在消失模铸造水基涂料中获得应用.     

铸铁件LFC法用涂料性能的研究

铸铁件消失模铸造技术(LFC法)用涂料选用石英粉、铝矾土、石墨粉和滑石粉为耐火材料;硅溶胶和聚乙烯醇为复合粘结剂;以钠基膨润土和羧甲基纤维素钠(CMC)为复合悬浮剂。通过测试各组涂料的悬浮性、p H值、透气性、密度、粘度、抗弯强度等性能指标,从而确定其最佳的涂料配方。实验表明此涂料可用于铸铁件的消失模铸造。     

粘结剂对消失模铸造涂料性能的影响

研究三种粘结剂对涂料性能的影响,分别对三种涂料的悬浮性、粘度、透气性、密度、常温抗弯强度和低温抗裂强度进行测定分析和比较,确定了铸铁件消失模水基涂料的最佳配比,并进行了生产验证。结果表明:以淀粉和硅酸钠为复合粘结剂是一种优良的粘结剂,其性能优良,并能很好地适应生产要求。     

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.     

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.     

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).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

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.     

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.