Fe表面层状结构的渗碳行为特性

将Q235钢放在改造后的电阻炉内,在通氢气的气氛中加热到1253K保温40min后随炉冷却,得到表面层为脱碳的两纯Fe试样。将其中一试样通过氧化-还原处理,使其表面具有层状结构,与另一脱碳试样一起放入改造后的电阻炉内,在通氢气的气氛中进行渗碳淬火。结果发现,具有层状结构试样的硬度明显高于脱碳试样的硬度；在光镜下观察两试样的截面,前者渗碳层的厚度明显大于后者。     

丙酮在UNICASE箱式多用炉上的应用尝试

将丙酮预先汽化后通入UNICASE滴注式箱式多用炉内作为渗碳气氛,可以改善工件表面质量,提高渗层、硬度均匀性。     

铁基粉末冶金从动轮零件热处理工艺改进

对类似FL4605铁基粉末冶金材料的从动轮零件经固体渗碳、重新加热淬火后.表观硬度严重不足的现象进行了原因分析.结果表明,渗碳后重新加热淬火,如果无保护性气氛保护,材料表面脱碳和氧化严重,油淬后硬度极低.为节省工时和成本,渗碳后采用保护性气氛加热直接淬火可以达到技术要求.     

丙酮在UNICASE箱式多用炉上的应用尝试

将丙酮预先汽化后通入ＮＩＣＡＳＥ滴注式箱式多用炉内作为渗碳气氛,可以改装工件表面质量,提高渗层,硬度均匀性。     

预抽真空可控气氛渗碳炉的工艺优化研究

建立渗碳过程中淬火前降温段不同的气氛组合,寻求预抽真空可控气氛渗碳炉(BBH)的热处理优化方案。采用硬度仪、光学显微镜对渗碳后试样进行分析。结果表明：在降温段使用氮气替代空气和甲醇,可以减轻试样的表面氧化程度,并且随着氮气用量的增加,试样的表面马氏体等级越高。当氮气和甲醇裂解气体比例控制在1:1.86时,试样的内氧化和非马氏体组织层深最浅。     

18CrNiMo7-6齿轮钢真空渗碳工艺研究

在轨道交通重载机车主动齿轮生产工艺中引入真空渗碳油淬工艺。研究主动齿轮18CrNiMo7-6材料的真空渗碳工艺,并与该齿轮常用的传统可控气氛渗碳工艺进行对比,对热处理后试样的碳浓度、硬度、有效硬化层深度、金相组织等进行检测分析。结果表明:该主动齿轮真空渗碳比传统可控气氛渗碳节约18%的工艺时间,且真空渗碳后的组织无内氧化、非马氏体等不良组织,马氏体、碳化物等组织级别均符合该机车主动齿轮技术条件。     

固态渗碳对Ti-6Al-4V合金及其复合材料(TiB+La_2O_3)/Ti-6Al-4V表面显微组织和硬度的影响（英文）

以Ti-6Al-4V合金和(TiB+La_2O_3)/Ti-6Al-4V复合材料为研究对象,研究固态渗碳法对两种材料表面显微组织和硬度的影响规律。将包覆于石墨粉中的试样置于密封的石英管中,在1227 K下保温24 h,成功实现了两种材料表面渗碳处理。显微组织和物相分析结果表明,固态渗碳后基体中原位生成了TiC增强体和Ti-C固溶体,且扩散层中的等轴α-Ti相的体积分数随试样深度增加呈明显降低趋势;硬度测试结果表明,两种材料渗碳表面的显微硬度与未处理材料相比都明显提高了约100%,随试样深度增加而变化的碳含量在渗碳试样中形成了约300μm的硬化层。同时,固态渗碳对内部组织和硬度的影响很小,表明该方法是一种有效强化钛合金及其复合材料的表面处理方法。     

喷油器体中孔硬度偏低的原因和预防措施

一种发动机喷油器体,材料为20CrMo钢,经渗碳、淬火和低温回火后发现,其中孔硬度不足。为揭示喷油器体中孔硬度偏低的原因,对制作喷油器体的原材料进行了化学成分分析,检测了毛坯件的显微组织和硬度,并对不合格的喷油器体进行了金相检验。结果表明,原材料和毛坯的质量均符合要求;但因喷油器体渗碳后出炉温度过高,导致其中孔表面脱碳,而且由于该中孔细而长,渗碳气氛流通不畅,导致渗层碳浓度偏低,这是喷油器体渗碳、淬火后硬度偏低的原因。采用乙炔真空渗碳工艺解决了喷油器体中孔硬度不足的问题。     

含纳米颗粒的铁基粉末冶金件直接渗碳工艺研究

在铁基粉末中分别添加纳米Fe和Cu颗粒混合，并对其粉末冶金件烧结时直接渗碳和烧结后渗碳的工艺进行实验研究，结果表明：直接渗碳的试样，在密度、表面硬度和有效硬化层硬度值均高于烧结后再进行渗碳试样的各项指标数据。     

渗碳过程的控制方法

本发明属于金属热处理及化学热处理的方法,涉及的是气体渗碳工艺和防止加热时脱碳的工艺。已为人们所知的渗碳过程的控制方法是:在炉气中碳的化学势偏离给定值时(用不同的仪器进行测量),改变通入炉内的渗碳剂。这种方法的缺点是只有采用吸热型气氛或放热-吸热性气氛作为气体介质时才能控     

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.     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.