钛铝异温轧制温度控制及复合性能研究

为实现钛铝异温轧制钛板电磁感应加热时温度分布更均匀,设计不同的感应加热线圈组对钛板进行加热,使用有限元模拟了电磁感应加热中感应线圈的结构参数对温度场的影响,通过调节感应加热参数将钛板宽度方向温差控制在50℃以内,形成较均匀的钛板温度。对钛板进行感应加热和测温实验,在较短时间的加热时长下形成了平均温度635℃,温差45℃以内的钛板温度,验证了仿真结果的正确性。对均匀性较好的高温钛板与室温铝合金板进行异温轧制,制备出界面剪切强度为63.3MPa的钛/铝复合板,并对制备出的钛/铝复合板结合性能的分布受温度均匀性的影响做了分析。     

金属材料超高速磨削温度场的实验研究与有限元仿真

在用热电偶进行磨削温度实验的基础上,分别运用解析法和有限元仿真法研究了金属材料超高速磨削的温度场,得出了其磨削温度场的分布;并分析了不同热源模型对温度场分布的影响.分析结果表明:随着Peclet数L值增大,磨削区热流分布从三角形变为均匀分布,且不同热源模型最高磨削温度相近,但出现的位置不同.     

宽台面单轴四点高速压力机温度场研究

针对阻碍宽台面单轴四点高速压力机实际应用的工作温升问题,研究了高速压力机热量产生机理,建立了热源分布模型,借助于ANSYS软件工具对温度场进行了数值仿真分析,揭示了温度分布与变化规律,在此基础上设计了高速压力机油冷冷却系统。数值仿真与实验研究结果均表明,在不采取任何散热或冷却措施时,高速压力机温度持续增高,达到热平衡的时间较长,热平衡点温度较高;采取强制油冷措施,可使高速压力机较快进入热平衡状态,并可将各运动部位工作温升控制在15℃之内,满足了实际应用要求。     

熔模铸造ZL114A铝合金凝固过程界面换热系数研究

为获得ZL114A铝合金在凝固过程中温度场的分布规律,根据实际工况设计了测温实验方案,利用热电偶和热成像仪得到了金属及其型壳在凝固过程中温度场的变化曲线,并根据实际测得的温度曲线借助ProCAST模拟软件中的反算模块对铸件与型壳间的界面换热系数进行了反求,得到了更加符合实际的界面换热系数。随后对其进行验证,用该界面换热系数所模拟求得的金属液温度曲线与实测值最大温差为10℃,型壳温度曲线与实测值最大温差为15℃,该方法及结果为铝合金熔模精铸模拟界面换热系数的设置提供了参考依据。     

高固相率SiCP/AZ61复合材料触变成形的数值模拟

采用等温热处理法制备SiCP/AZ61复合材料半固态坯料,在自制实验装置上进行触变成形实验.采用所建立的高固相率SiCP/AZ61复合材料本构模型,对触变成形过程进行了数值模拟,得到了不同成形温度下的应力、应变和温度场分布.结果表明,与成形温度为530℃相比,560℃时复合材料触变成形具有变形抗力小、应变与温度场分布均匀的特点.通过实验和模拟结果对比可知(成形温度为560℃),两者吻合较好,所获结果可指导高固相率镁基复合材料触变成形工艺实践.     

16MN螺旋压力机上下加温模座及其恒温控制系统研究

为克服传统加工方式的弊端,设计16 MN螺旋压力机上下加温模座并进行基于PLC的恒温控制系统的实验研究。进行上下模座的结构设计及强度校核,采用基于目标值滤波的二自由度PID控制算法实现了恒温模座闭环控制系统。实验结果表明:模座结构合理,强度满足要求;上下模座加热棒选用得当、分布合理,模座温度分布均匀;在2 h内,模座可由常温加热到350℃;上下模座温差小,控制精度高。     

A-100钢复杂连接件热处理畸变数值模拟及控制

采用SYSWELD软件对A-100钢复杂连接件进行了有限元建模,对其在无刚性约束条件下淬火过程中温度场和形变进行了模拟仿真,并对模拟结果进行了试验验证。温度场结果表明:冷却0.13 s时温度分布均匀,零件表面温度在820 ℃左右;冷却5~60 s时,零件表面的温度分布极为不均匀,零件头部型腔的棱角处温度较低,而位于底部的支臂与翼面连接处温度较高;而当冷却时间延长至160 s左右时,零件的整体温度已降至60 ℃以下。形变场结果表明:当冷却时间为0.5~10 s时,翼面远离加强筋部位产生较大淬火畸变,顶端棱角处畸变达3 mm;冷却到600 s时,最大畸变量减小至0.65 mm。根据畸变模拟结果设计了专用淬火工装,校形率达到70%左右。     

车用铝材分流模挤压过程温度场分析

为了对汽车用铝材分流模挤压过程的温度场分布进行分析,根据刚塑性有限元基本原理,利用数值模拟技术对其进行评估.分析了挤压速度及摩擦因子对坯料截面不同方向(平行及垂直挤压方向)的温度场分布的影响,选取特征点对焊合区域的温度场分布进行研究.对数值模拟结果进行分析可知,当坯料初始温度为450℃,摩擦因子为0.3时,挤压速度由1增至3mm·s-1时,温度最大值与最小值的差值在X方向上由7℃增至8℃、在Y方向上由9℃增加到10℃;通过对温度场的分析发现:具有良好散热条件的挤压筒壁附近的特征点温度出现一定程度的下降,而一些位于内部的特征点热损失很小,而且与坯料间具有不同程度的热交换,因此温度下降幅度小,在某些点上甚至出现了反常升高.     

氮化硅陶瓷干湿磨削温度与表面质量研究

为研究干湿磨两种条件下氮化硅陶瓷温度场特性,以及磨削力、温度场特性与表面质量三者间的关系。在理论分析的基础上运用ABAQUS有限元软件对其进行仿真,最后通过实验分析干湿磨条件下的温度场对其表面特性的影响。得出在干湿磨两种条件下的磨削力与磨削区温度场的关系以及磨削温度场的分布情况;并分析了温度场对其热裂纹的影响与温度和其表面特性的关系。得出磨削力是影响磨削区温度场变化的主要因素;随着磨削表面下深度的增加,湿磨下磨削温度的幅度变化要大于干磨,且磨削温度的幅度变化对其表面特性与裂纹的产生有所影响;干磨条件下的表面粗糙度与微观形貌要优于湿磨条件下。     

汽车前防撞梁热成形冷却过程温度场数值模拟

采用ProCAST软件,对高强钢板热冲压成形工艺冷却(淬火)过程进行数值模拟分析,计算了连续多个冲压工作循环下模具和坯料的温度场。结果表明,模具在连续多个冲压工作循环中,温度呈周期性的快速上升和快速下降的变化趋势,当每一个冲压工作循环结束时,模具的温度都保持在50℃左右。坯料在淬火过程中,其温度呈快速降低趋势,冲压结束时坯料的出模温度分布在75℃²25℃上下,出模温度随冲压工作循环的进行而依次略有升高,并达到稳定。对模具和坯料进行试验测试,其温度值与数值模拟值吻合较好,说明该计算模型和方法对成形工艺设计有较好的预测评价作用。     

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.