球墨铸铁管卡脆断原因分析

从宏观断口形貌、金相显微组织、化学成分等方面分析了球墨铸铁管卡脆断的原因。脆断管卡断口存在大面积白口组织是其脆断的直接原因。金相分析表明,珠光体含量和游离渗碳体含量越多,管卡的脆性越严重。本文进一步分析了各种化学元素对铸态球墨铸铁组织的影响,结合工艺过程的仔细调查,确定Cr、Mn含量高是球墨铸铁管卡脆断的主要原因,并给出稳定球墨铸铁管卡质量的措施。     

球铁凸轮轴脆断原因分析

利用扫描电镜及能谱仪等现代测试仪器，对球铁凸轮轴脆断原因进行了综合分析。结果表明，其脆断原因系材料本身的w（P）量超标所致。其次是因其珠光体量过高，导致材料的疲劳强度下降而致脆。     

20g中板埋弧焊冷弯脆断的原因及解决措施

通过对两批有代表性的２０ｇ中板埋弧焊试板的冷弯对比试验，探讨了２０ｇ中板埋弧烛试板的冷弯对比试验，探讨了２０ｇ中板埋弧焊后产生冷弯脆断的主要原因，通过调整焊接工艺，使这些２０ｇ中板弧焊冷弯脆断现象得以解决。     

20钢环锻件拉伸试棒脆断原因分析

采用化学成分分析、金相检验、扫描电镜及能谱分析等方法对20钢环锻件拉伸试棒脆断原因进行了分析。结果表明,锻件内部氢含量较高,从而产生白点;在拉伸应力作用下非金属夹杂物产生应力集中并形成圆形白亮斑点。这些是拉伸试棒脆断的主要原因。     

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 35CrMoA钢棒材在生产热模锻连杆结构件时发生了脆断,为了找出脆断产生原因,采用金相显微检验、SEM断口观察、X射线能谱分析等方法对其脆断原因进行了分析,结果表明：连杆结构件发生的脆断,主要是由于过烧的作用导致晶界明显弱化产生的。     

高碳钢盘条脆断原因分析

用金相法分析了高碳钢盘条脆断机理.结果表明,高碳钢盘条脆断主要因运输过程中的碰撞和磨擦,使盘条表面发生马氏体相变,使盘条脆断.提出了相应的防范措施.     

20MnSi热轧带肋钢筋冷弯脆断和无屈服点原因分析

分析和研究了20MnSi热轧带肋钢筋在常规力学性能检验中偶然出现冷弯脆断和无屈服点异常现象的原因。结果表明：钢中存在一定量异常粒状贝氏体组织，是20MnSi热轧带钢筋产生冷弯脆断或在拉伸检验时出现无屈服点的主要原因。     

Pt-10Rh/Pt热偶在还原气氛中脆断失效分析

试验证实了高温下Ｐｔ－ １０Ｒｈ／Ｐｔ 热偶在Ｈ２ 或ＣＯ 气氛中使用时因脆性而会很快断裂失效。采用透射电镜（ＴＥＭ） 对脆断偶丝进行微观组织和形貌观察, 定性定量研究认为：脆断失效的根本原因在于Ｓｉ 与Ｐｔ 作用形成Ｐｔ５Ｓｉ２ 低溶点共晶物, 使偶丝局部熔点降低而熔化, 发生脆断。脆断处局部区域Ｓｉ 最大含量分别达到７．９３ ％ 和３．２７ ％ , 而Ｓｉ 是高温下耐火材料中ＳｉＯ２ 被Ｈ２ 或ＣＯ 还原产生的。     

HRB400带肋钢筋盘条脆断原因分析

通过对HRB400带肋钢筋盘条脆断试样进行金相组织、晶粒度、微区成分偏析、非金属夹杂物的检测分析,找出了盘条脆断的原因,即盘条在斯太尔摩辊道上的风机开启区域“打爬行”,冷却时间过长,产生了脆性组织,使盘条局部塑性降低,产生脆性断裂。     

HRB335热轧带肋钢筋脆断原因分析

采用化学分析、金相组织检验、力学性能检验和热处理实验等手段，对HRB335热轧带肋钢筋出现拉伸脆断和无屈服强度的异常现象进行分析。结果表明，HRB335热轧带肋钢盘出现一定量异常组织粒状贝氏体是拉伸脆断和无屈服强度现象的主要原因。     

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.