Microstructures and mechanical properties of 2014 aluminium alloy forgings made by a new process

The triangular 2014 aluminium alloy forgings were made by a new process and the traditional process. The results showed that the mechanical properties of the forgings made by the new process are far higher than that in the standard of GB223 84, and also higher than that in the standard of EL/53MI 94; moreover, the mechanical properties are almost the same in each direction, and anisotropies are very small. The grains and 2nd phases were analyzed by using TEM and SEM, the results indicate that very fine grains (3～6 μm)appear in an approximately isometric way, and a large number of 2nd submicrophases(0.05～0.15 μm) disappear in no apparently preferred orientation distribution because the new process involves multidirectional heavy plastic deformation (λ=12), solution(500 ℃/400 min) and ageing(165 ℃/10 h) heat treatments for a long time at high temperatures. These refined grains, 2nd submicrophases and their almost homogeneous distribution can make it possible for the forgings to display high mechanical properties.

STUDY ON THE FORMATION OF DEFECTS IN DURALUMIN FORGINGS

The mechanism of forming defects in 2024. 7075 series aluminium alloy forgings has been studiedby means of metallography. EDAX. SEM etc. The defects are divided into two types by their appearance.needle-shaped and flake-shaped. The mechanism of them forming is discussed. It has been testified that thedefects result from hydrogen or oxide film. The defects can be prevented by controlling the hydrogen contentin the melt and keeping oxide film from involving.

MICROSTRUCTURAL EVOLUTION AND CONTROL IN SUPERALLOY FORGINGS

Optimum properties of high temperature superalloys are derived from interactions of the composition,thermomechanical deformation, and heat treatment.Nickel-base alloys contain a variety of alloying elements in a large number of combinations to produce various desired effects. The general characteristics of any specific nickelbase superalloy is determined by composition.The control of the microstructure in wrought processed superalloys can further influence the resultant component properties.The relationship between microstructure and properties is key in advanced design and manufacture of turbine engine components, and requires extensive alloy and process characterization to achieve desired results.Various forging methods have been developed and employed throughout the years to process superalloy components.Hammer forging, Press forging,and advanced isothermal press forging equipment and processes have been designed and manufactured to process speciality metals which often have very narrow processing windows.Combination processes have also been introduced into turbine engine applications,which result in a hybrid of resultant structures and properties.One such speciality,combination process is the Ladish Iso Con process which utilizes isothermal forging and conventional forging to achieve unique properties not matched by any other single process.Ladish utilizes forging presses for conventional forging, hot-die forging and for isothermal forging, in addition to hammers and ring rolling mills for wrought processing.This wide range of equipment allows flexibility in process design and optimization.Variations in temperature, strain and strain rate have been shown to significantly influence resultant grain sizes and microstructures.Tools are being developed to allow forging processes and specific forging parameters to be evaluated and optimized with regard to final microstructure before shop triale are required. Sophisticated finite element method (FEM) models are allowing the design of forging processes on computers rather than by iterative trial and error methods.

Research on Voids Deformation Welding Condition for Manufacturing of Heavy Forgings

Crushing and diffusion welding are two critical healing stages of interior void defects in heavy forgings.The healing result depends on many factors during the forging process,such as stress,temperature,deformation and type of material,while the void diffusion welding condition is still not well known at the present.This paper is concerned with the deformation welding condition of the closed void interface in heavy ingot during the hot forging process.A void crushing experiment is carried out to recognize the microstructure of the closed void interface.According to the healing mechanism at high temperature,a new physical simulation model is setup to study the deformation welding process of the closed void interface based on the theory of atom diffusion and the interface contact mechanics prototype.Compared with the experimental results,the influence of deformation degree,forming temperature and holding time on the welding quality is discussed,and then the deformation welding condition of closed void interface is presented.The proposed condition helps to improve forging technology and product quality.

New Microalloyed Steels for Forgings

Microalloyed steels for forging applications have been newly developed in order to increase strength and toughness properties which thereby give the possibility for light weight constructions.The properties of these steels are set up by a controlled cooling directly from the forging heat without an additional heat treatment.This aim can be achieved on the one hand by a further development of precipitation hardening ferritic pearlitic steels (AFP-steel) due to an extended use of microalloying elements (AFP-M steel) and on the other hand by microalloyed steels which employ a bainitic microstructure (HDB steel).To adjust the targeted microstructure the temperature control has to be assured down to approx.500℃ for the AFP-M steels and down to approx.300℃ for the HDB steels.

Simulation-Based Investigation of Crack Formation in Forged MB15 Magnesium Alloy

In the process of riveting an MB15 forging die,cracks were discovered emerging along the longitudinal direction and near the riveting hole.Through fracture analysis,microscopic observation,energy spectrum analysis,metallographic examination,and hardness test,the properties and causes of the cracks are discussed.The results indicate that the cracking type is intergranular brittle cracking,occurring during the forging stage.Furthermore,the recrystallization at the crack site is found to be incomplete,which is attributed to the low deformation temperature.

Call for Papers for the Special Issue on"Large Castings and Forgings"

Large castings and forgings play a crucial role in development of society and economy.The products of large castings and forgings are the fundamental of heavy equipment,which are widely used as the funda-mental components of many industries,e.g.,electric power,metallurgy,petroleum and chemical,ship-building,railway,mining,aerospace.Over the past decades,many studies have been performed with re-spect to smelting,casting,heat treatment and forging and relevant technologies have made a great advance.Nevertheless,there still are some problems to be solved,which limit the development of casting and forging industries,including macrosegregation,large size inclusion,shrinkage and porosity and low production yield.

Call for Papers for Special Issue on“Large Castings and Forgings”

Large castings and forgings play a crucial role in development of society and economy.The products of large castings and forgings are the fundamental of heavy equipment,which are widely used as the fundamental components of many industries,e.g.,electric power,metallurgy,petroleum and chemical,shipbuilding,railway,mining,aerospace.Over the past decades,many studies have been performed with respect to smelting,casting,heat treatment and forging and relevant technologies have made a great advance.

老年公寓建筑数字孪生模型联合仿真疏散模拟方法

建筑数字孪生模型(BDT)是数字孪生(DT)应用到建筑业中与BIM结合的集成模型,能反映现实建筑运营情况.在数字孪生驱动下老年公寓消防安全和居住质量能得到进一步提升,因此提出一种老年公寓数字孪生模型联合仿真疏散模拟方法,用于老年公寓消防安全评估和设计优化.为验证方法可实施性,以大庆市某老年公寓为例,利用BDT模型和BIM分别进行仿真模拟,结果显示两者疏散时间相差较大,影响到其消防安全性判断,老年公寓BDT模型联合仿真模拟相比于其BIM模型单一空间仿真模拟,更能真实反映老年人群在火灾场景下疏散情况,根据方法框架得出算例老年公寓存在消防安全问题,提出消防改造和疏散优化策略并验证.

Effect of heat treatment on the microstructure and mechanical properties of a multidirectionally forged Mg-Gd-Y-Zn-Zr-Ag alloy

Multidirectional forging(MDF)was successfully applied to fabricate large-size Mg-Gd-Y-Zn-Zr-Ag alloy in this work and effects of T4,T5 and T6 treatments on the microstructure and mechanical properties of the as-forged alloy were analyzed.Results show that dynamic recrystallization(DRX)occurs and second phase particles precipitate along the grain boundary during the MDF process.After annealing treatment(T4),the volume fraction and size of dynamic precipitates slightly increase at a lower temperature(430℃)compared with those of MDFed sample,while they are dissolved into theα-Mg matrix at a higher temperature(450℃).At the meantime,short plate-shaped long-period stacking ordered(LPSO)phases are observed in the DRX grains of the MDFed sample and then dissolved into theα-Mg matrix during annealing at both temperatures.Typical basal texture is identified in the MDFed sample,but the basal pole tilts away from final forging direction and rare-earth texture component with<1121>orientation parallel to penultimate forging direction becomes visible after annealing.The T6 sample annealing at 430℃for 4 h and ageing at 200℃for 34 h exhibits the superior strength and ductility in this study.The ultimate tensile strength,tensile yield strength and elongation to failure,which is 455 MPa,308 MPa and 7.7%,respectively,are overall improved compared with the directly-aged(T5)sample.This paper provides a superior heat treatment schedule to manufacture high-performance large-scale Mg-Gd-Y-Zn-Zr-Ag components for industrial production.

Texture Engineering to Boost the Thermoelectric Properties

A round 60% of useful energy is wasted in industry, homes, or transportation. Therefore, there has been increasing attention on thermoelectric materials for their ability to harvest waste heat into useful energy. The efficiency of a thermoelectric material depends on its electrical conductivity, Seebeck coefficient, and thermal conductivity in a conflicting manner which results in efficiency optimization challenges. Single crystals and polycrystalline layered materials have comparatively better thermoelectric and mechanical properties in a certain direction. Texture engineering is a special strategy that allows the exploitation of superior material properties in a specific direction. Texturing could be achieved by various sintering and deformation methods, which yield defects improving thermoelectric and mechanical properties. The results show that for(Bi,Sb)_(2)Te_(3), Bi_(2)(Se,Te)_(3), C uSbSe_(2), and SnSe, significant enhancement in the thermoelectric figure of merit is achieved by enhancing the preferred orientation. Texture engineering provides a wide range of strategies to elevate the zT of anisotropic materials to values comparable to those of their single crystalline counterparts.

Effect of nitrogen content on the microstructure and mechanical properties of titanium-bearing nonquenched and tempered steel after hot forging

The microstructure and mechanical properties of titanium(Ti)-bearing medium-carbon nonquenched and tempered steel with different nitrogen content before and after hot forging were investigated through smelting,forging,and laboratory tests.The results show that the grain size of nonquenched and tempered steel was gradually refined,and the ferrite content gradually increased with an increase in nitrogen content.The grain size of the material with low nitrogen content increased abnormally,and its impact properties significantly decreased after hot forging.The grain size of nonquenched and tempered steel with higher nitrogen content was slightly larger than that before forging,and the tensile and yield strength increased,but the impact toughness was not significantly reduced.The Ti-bearing nonquenched and tempered steel showed better strength and toughness after hot forging with the addition of 0.010%0.015%nitrogen.

Blockchain-Based Certificate Authentication System with Enabling Correction

Blockchain has proven to be an emerging technology in the digital world, changing the way everyone thinks about data security and bringing efficiency to several industries. It has already been applied to a wide range of applications, from financial services and supply chain management to voting systems and identity verification. An organization must verify its candidates before selecting them. Choosing an unqualified candidate can ruin an organization’s reputation. In this paper, a blockchain-based academic certificate authentication system will be used to ensure authenticity and make the assertion of the decentralized system secure. However, the system will generate, authenticate and make corrections on academic certificates. Ultimately, some blockchain-based authentication systems already exist, they can’t correct any errors that occur during generation. A blockchain-based certificate authentication system was built using blockchain technology. Where admin could generate, authenticate and correct the certificate if necessary. The admin can also check how many times a certificate has been modified. Other users can only check the authenticity of the certificates. We’re using two blockchains to enable corrections. Blockchain technology can successfully implement a certificate authentication system. This system will eliminate doubts about the authenticity of certificates, provide fast responses, and ensure reliable and secure storage. The proposed system will help in many ways, such as providing a user-friendly university admission, and smooth job hiring process, etc. In conclusion, our proposed system can permanently eradicate certificate forgeries and create and promote trust in society.

桌面式五轴联动数控加工中心

当前数控加工向高精度、高速度、高柔性、体系开放化方向发展。五轴联动数控机床可以加工工艺复杂的零件,但因技术难度大、造价昂贵,致使大多数高等院校无法购买,这阻碍了五轴联动数控机床先进制造技术在国内的普及,也阻碍了中国制造业的快速发展。本产品作为新一代桌面式微小型数控机床,主要运用于高校教学和实验等场景。

Fostering Chinese National Unity:Advocating the National Common Language and Writing System for Heightened Community Awareness

The promotion of the national common language and writing system stands as a cornerstone in cultivating a sense of community among the Chinese nation.The national common language and writing system,serving as a potent vehicle for cultural dissemination and linguistic communication,acts as a crucial bridge fostering unity,mutual support,cultural exchange,and cohesion among diverse ethnic groups.Its widespread promotion not only reinforces the cohesion of the Chinese nation but also plays a pivotal role in fortifying national and cultural identity.The advocacy and dissemination of the national common language and writing system contribute significantly to enhancing the sense of community within the Chinese nation.This concerted effort serves as an internal driving force,creating a positive feedback loop that strengthens both national identity and the cultural bonds shared by the Chinese people.The reciprocal relationship between the promotion and popularization of the national common language and writing system reinforces a mutual sense of assistance and reciprocity.This bidirectional dynamic propels a synergistic interplay,fostering a beneficial cycle in the promotion and widespread adoption of the national common language and writing system.In essence,the promotion and popularization of the national common language and writing system not only contribute to its advancement but also serve to deepen the sense of community within the Chinese nation.This reciprocal interaction between the two elements establishes a robust foundation for nurturing a strong and cohesive Chinese community.

Effects of heat treatment on the microstructures and mechanical properties of a new type of nitrogen-containing die steel

Nitrogen can increase the strength of steels without weakening the toughness and improve the corrosion resistance at the same time. Compared with conventional nitrogen-free die steels, a new type of nitrogen-containing die steel was developed with many superior properties, such as high strength, high hardness, and good toughness. This paper focused on the effects of heat treatment on the microstruc- tures and mechanical properties of the new type of nitrogen-containing die steel, which were investigated by the optimized deformation process and heat treatment. Isothermal spheroidal annealing and high-temperature quenching as well as high-temperature tempering were ap- plied in the experiment by means of an orthogonal method after the steel was multiply forged. The mechanical properties of nitro- gen-containing die steel forgings are better than the standard of NADCA #207-2003.

芯辊进给方式对辗环成形的影响

芯辊进给速度是径轴向环形辗扩成形的重要工艺参数。本文根据热辗扩的成形特点,用锻造软件Forge对芯辊三种不同进给方式(恒定进给速度、恒定每转进给量、恒定外半径增长速度)时径轴向辗环过程进行了数值模拟,分析了三种不同的芯辊进给方式对辗环成形的影响。结果表明,芯辊以恒定外半径增长速度进给时,轧件温差为88.738℃,是三种进给方式中温差最大的。这不利于控制轧制过程中温度的稳定性。

矿用液压软管接头芯子径向锻造工艺的研究

目的随着我国煤炭、钢铁业的新发展,矿用液压软管接头因更换快、使用量大,迫切需要新的成形工艺。方法针对KJ-25型液压软管接头芯子,提出了一种采用径向锻造近净成形制造毛坯的工艺。通过三维有限元软件FORGE建立了工艺的三维有限元模型,并对成形力、工件温度及应力状态进行了分析。结果有限元模拟结果表明:径向锻造生产的坯料较切削加工可节材37%,温锻时单个锤头锻造力仅为37.3 t。结论径向锻造工艺适用于同类型软管接头芯子的毛坯制造。

深型腔模具精密加工技术的研究与实现

针对淬硬工具钢切削性能差、深型腔模具加工廓形精度不易保证等问题,提出了一种深型腔模具精密高速加工工艺优化技术。该技术根据构建的加工刀轨长度以及刀具悬伸长度与型腔加工廓形误差之间的数学模型,计算随加工刀轨长度变化的廓形误差值,设计瞬时的螺旋线加工刀轨,运用曲线过渡法,生成了适合深型腔模具精密高速加工的优化刀轨。基于米克朗Duro800高速加工机床,对内星轮模具型腔进行精密加工,结果表明,加工精度可提高IT1～2级,表面粗糙度Ra≤0.8。