热处理工艺和充氢对GCr15SiMoAl轴承钢压缩性能的影响

经成分优化获得一种新型的贝氏体轴承钢GCr15SiMoAl,通过盐浴等温淬火不同时间及油淬工艺获得不同的组织,利用Gleeble3500研究了试验用钢充氢前后的压缩变形行为,并与常规的GCr15轴承钢进行了对比。结果表明,GCr15SiMoAl轴承钢经0.5h等温获得了贝氏体铁素体、残留奥氏体及马氏体的复合组织,其综合压缩性能最好;随着盐浴等温时间的延长,抗压强度逐渐降低,相对压缩率先升高后降低。且GCr15SiMoAl轴承钢在所有工艺下获得的性能均优于传统的GCr15轴承钢。氢对轴承钢的抗压强度影响较小,但是由于氢会促进残留奥氏体发生应变诱发马氏体转变,严重降低了轴承钢的塑性。     

12MnNiVR钢的连续冷却转变行为及相变动力学

用热膨胀仪测定了12MnNiVR钢的连续冷却转变曲线,并结合显微组织观察和硬度测定,研究了低冷速下奥氏体向铁素体转变及向贝氏体转变的动力学,分析了铁素体转变及贝氏体转变的生长方式.实验钢在连续冷却过程中的计算相变动力学结果与实测相变数据吻合很好.研究结果表明实验钢在低冷速下冷却时奥氏体向铁素体转变,形核位置主要在晶棱处,生长方式主要为二维长大,奥氏体向贝氏体转变,形核位置主要在界面处,生长方式主要为一维长大.     

GCr18Mo轴承钢复相组织对强韧性影响

对GCr18Mo轴承钢中下贝氏体-马氏体(简称B下／M)复相组织的强韧性进行了研究，结果表明：随下贝氏体量的增加，其冲击韧度、断裂韧性逐渐升高，抗弯强度先增加而后下降；与单-马氏体组织相比,B下／M复相组织具有更好的强韧性；B下／M复相组织的冲击韧度与下贝氏体量呈线性关系；下贝氏体体积分数为37．5％的B下／M复相组织具有最佳的综合力学性能。     

GCr15轴承钢贝氏体-马氏体复相淬火北大核心CSCD

利用光学显微镜(OM)和扫描电子显微镜(SEM),对GCr15轴承钢贝氏体-马氏体(B-M)复相淬火进行的研究。分析了等温淬火温度和保温时间、奥氏体晶粒尺寸、球化组织中渗碳体颗粒的单位体积密度对B-M复相淬火的影响规律。结果表明:等温淬火保温时间为30 min时,270℃淬火有利于下贝氏体的转变;等温淬火温度为240℃时,保温60 min有利于下贝氏体的转变。当渗碳体单位体积密度达到3.45个时,贝氏体铁素体片条变细,试验钢硬度升高。     

GCr15轴承钢贝氏体-马氏体复相淬火

利用光学显微镜(OM)和扫描电子显微镜(SEM),对GCr15轴承钢贝氏体-马氏体(B-M)复相淬火进行的研究。分析了等温淬火温度和保温时间、奥氏体晶粒尺寸、球化组织中渗碳体颗粒的单位体积密度对B-M复相淬火的影响规律。结果表明:等温淬火保温时间为30 min时,270℃淬火有利于下贝氏体的转变;等温淬火温度为240℃时,保温60 min有利于下贝氏体的转变。当渗碳体单位体积密度达到3.45个时,贝氏体铁素体片条变细,试验钢硬度升高。     

第一代、第二代和第三代轴承钢及其热处理技术的研究进展(一)

按搜集的近一二十年来很多和很新的资料加以比较详细综述,阐明轴承钢的主要类型;GCr15钢的球化退火; GCr15钢的淬火回火组织结构; GCr15钢的贝氏体转变;残余奥氏体、纳米贝氏体和纳米析出相;淬火-分配QP处理;光学显微镜下出现黑、白的腐蚀区分析;第2、第3代轴承钢的组织转变与性能;轴承钢的纯净度和非金属夹杂物以及双真空冶炼技术;航空轴承用钢的双重(复合)硬化处理等。试着为我国轴承钢研究方面的突破性进展作出努力。     

Mo对09CuPCrNi耐候钢连续冷却转变的影响

测定了09CuPCrNi耐候钢的连续冷却转变动力学图（CCT曲线）,并对不同冷速下的组织进行了观察。与传统09CuPCrNi耐候钢的CCT曲线相比,加入0．33％（质量分数,下同）的Mo后,贝氏体转变区与铁素体转变区部分分离;加入0．41％的Mo后,贝氏体转变区与铁素体转变区完全分离,同时珠光体转变区与铁素体转变区也完全分离。     

Mo和Ni对低合金耐磨钢连续冷却转变的影响

用热力模拟实验机测定了不含Mo和Ni、含Mo不含Ni、含Mo和Ni 3种成分低合金耐磨钢的连续冷却转变(CCT)曲线,用光学显微镜、透射电镜观察了连续冷却过程中的显微组织,研究了连续冷却条件下的组织演变规律,分析了Mo和Ni元素对显微组织和硬度的影响。结果表明:随冷速的增加,试验钢的转变组织主要有铁素体、粒状贝氏体、板条贝氏体以及板条马氏体。Mo、Ni的添加使耐磨钢在低冷却速率下抑制了铁素体相变,促进了贝氏体相变;在高冷却速率下促进了马氏体相变,提高了临界冷却速率。Ni的添加对显微硬度的增加作用更明显。     

钼含量对微合金铸钢组织及性能的影响

借助熔炼制备合金的方法以及OM、SEM研究和分析了Mo的添加对微合金铸钢组织和性能的影响。试验结果表明;正火后随Mo含量增加,组织中珠光体、铁素体数量减少,贝氏体铁素体数量增加。回火后组织中的贝氏体铁素体转变为铁素体和渗碳体粒子;随Mo含量增加,纽扣铸锭试样的硬度、强度增加,塑性降低;拉伸断口韧窝尺寸与深度均减小。     

20MnCrNi2Mo铸钢贝氏体形核-长大过程的原位观察

以添加稀土的20MnCrNi2Mo铸钢为研究对象,采用L78 RITA淬火热膨胀仪测定了其连续冷却转变(CCT)曲线,为制定合适的贝氏体转变工艺提供依据。采用激光扫描共聚焦显微镜(LSCM),并配以高温热台,对试验钢贝氏体形核-长大过程进行原位观察。结果表明,添加稀土20MnCrNi2Mo铸钢的贝氏体铁素体优先在晶界形核,也可以在晶内形核;贝氏体铁素体片可以向晶内生长,也可侧向激发形核长大,最终生长为不同形貌的贝氏体。贝氏体形核区域具有多样性,生长过程呈现复杂性。     

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.