Progress in weldability research of duplex stainless steels

Duplex stainless steels(DSSs)show better corrosion resistance with higher strength than traditional austenite stainless steels in many aggressive environments,and can be welded properly with almost every welding processes,if proper heat input is provided.Progresses of research works on weldability of DSSs in recent years are reviewed in this paper.Balance control of ferrite/austenite phases is most important for DSSs welding.The phases balance can be controlled with filler materials,nitrogen addition in shielding gas,heat input,post weld heat treatment,and alternating magnetic field.Too high cooling rate results in not only extra ferrite,but also chromium nitride precipitation.While too low cooling rate or heating repeatedly results in precipitation of secondary austenite and intermetallic compounds.In both situations,mechanical properties and corrosion resistance of the DSS joints deteriorate.Recommended upper and lower limits of heat input and maximum interpass temperature should be observed.

Optimization of process parameters of the activated tungsten inert gas welding for aspect ratio of UNS S32205 duplex stainless steel welds

The activated TIG(ATIG) welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much attention.The shape of a weld in terms of its width-to-depth ratio known as aspect ratio has a marked influence on its solidification cracking tendency.The major influencing ATIG welding parameters,such as electrode gap,travel speed,current and voltage,that aid in controlling the aspect ratio of DSS joints,must be optimized to obtain desirable aspect ratio for DSS joints.Hence in this study,the above parameters of ATIG welding for aspect ratio of ASTM/UNS S32205 DSS welds are optimized by using Taguchi orthogonal array(OA)experimental design and other statistical tools such as Analysis of Variance(ANOVA) and Pooled ANOVA techniques.The optimum process parameters are found to be 1 mm electrode gap,130 mm/min travel speed,140 A current and 12 V voltage.The aspect ratio and the ferrite content for the DSS joints fabricated using the optimized ATIG parameters are found to be well within the acceptable range and there is no macroscopically evident solidification cracking.

Duplex Detection of Vibrio Cholerae and Vibrio Parahaemolyticus by Real-time Recombinase Polymerase Amplification

Vibrio cholerae and Vibrio parahaemolyticus are the two most commonly reported pathogens in seafood[1]. Consuming raw or undercooked seafood contaminated with these two Vibrio species can cause food poisoning, posing the risk of severe gastrointestinal illness and death[2-3]. Therefore,precise and reliable methods for detecting V. cholerae and V. parahaemolyticus contamination in seafood are essential for controlling food safety.

Comparative research on the mechanical property and precipitation of the 2101 and 2205 duplex stainless steels

The mechanical property and precipitation of the 2101 and 2205 duplex stainless steels were investigated. The results show that with nitrogen-content increasing from 0.12% to 0.26% to partly replace nickel ,the yield strength of the 2101 steel gains an increase of 80 MPa whilst its elongation proportion keeps unchanged. The impact energy at a low temperature is obviously reduced. The temperature at which the impact energy starts decreasing is lower than 20℃, -20℃ and - 40℃ for the 2101 steels containing 0.5 % Ni, 1.5 % Ni and 2.5 % Ni respectively, whereas it is - 70℃ for the 5 % Ni- containing 2205 steel. The nose temperature of precipitation is 700℃ for the 2101 steel and 850℃ for the 2205 steel. The scanning electronic microscope （SEM） ,the transmission electron microscope （TEM） and the X-ray diffraction （XRD） analyses show that the drop in the impact energy of the 2101 steel can be mainly attributed to the precipitation of Cr2N upon ageing while it is attributed to the sigma phase for the 2205 steel.

Effect of Laser Beam Welding Parameters on Microstructure and Properties of Duplex Stainless Steel

The present study is concerned with laser beam welding and its effect on size and microstructure of fusion zone then, on mechanical and corrosion properties of duplex stainless steel welded joints. In this regard, influence of different laser welding parameters was clarified. Both bead-on-plate and autogenously butt welded joints were made using carbon dioxide laser with a maximum output of 9 kW in the continuous wave mode. Welded joints were subjected to visual, dye penetrant and radiography tests before sectioning it for different destructive tests. Accelerated corrosion test was carried out based on tafel plot technique. The results achieved in this investigation disclosed that welding parameters play an important role in obtaining satisfactory properties of welded joint. High laser power and/or high welding speed together with adjusting laser focused spot at specimen surface have produced welded joints with a remarkable decrease in fusion zone size and an acceptable weld profile with higher weld depth/width ratio. Besides, acceptable mechanical and corrosion properties were obtained. Using nitrogen as a shielding gas has resulted in improving mechanical and corrosion properties of welded joints in comparison with argon shielding. This is related to maintaining proper ferrite/austenite balance in both weld metal and HAZ in case of nitrogen shielding. As a conclusion, laser power, welding speed, defocusing distance and type of shielding gas combination have to be optimized for obtaining welded joints with acceptable profile as well as mechanical and corrosion properties.

Developing a duplex ARMS-qPCR method to differentiate genotype Ⅰ and Ⅱ African swine fever viruses based on their B646L genes

Africanswinefever(ASF),causedbythe African swine fever virus (ASFV), is an acute, hemorrhagic, and contagious disease of domestic pigs and wild boars.The disease is notifiable and listed by the World Organization for Animal Health (WOAH)(Wang N et al. 2019).

Joint Flexible Duplexing and Power Allocation with Deep Reinforcement Learning in Cell-Free Massive MIMO System

Network-assisted full duplex(NAFD)cellfree(CF)massive MIMO has drawn increasing attention in 6G evolvement.In this paper,we build an NAFD CF system in which the users and access points(APs)can flexibly select their duplex modes to increase the link spectral efficiency.Then we formulate a joint flexible duplexing and power allocation problem to balance the user fairness and system spectral efficiency.We further transform the problem into a probability optimization to accommodate the shortterm communications.In contrast with the instant performance optimization,the probability optimization belongs to a sequential decision making problem,and thus we reformulate it as a Markov Decision Process(MDP).We utilizes deep reinforcement learning(DRL)algorithm to search the solution from a large state-action space,and propose an asynchronous advantage actor-critic(A3C)-based scheme to reduce the chance of converging to the suboptimal policy.Simulation results demonstrate that the A3C-based scheme is superior to the baseline schemes in term of the complexity,accumulated log spectral efficiency,and stability.

Investigation on influence of alloying on phase transitions of duplex stainless steel based on thermochemical calculation

This paper investigated on influence of different alloying elements added into duplex stainless steel (DSS) on phase transitions using thermochemical methods in comparison with experiment.The results showed that the most possible species in the ferrite phase,austenite phase,σphase,Hcp phase,χphase,and carbide were Cr:Va-type,Fe:Va-type,Ni:Cr:Mo-type,Cr_(2)N-type,Fe_(24)Mo_(10)Cr_(24)-type,and Cr:Mo:C-type,respectively.Furthermore,the Ni,N,Cr,and Mo alloying had significant influences on the transition of each DSS phase.The Ni and N additions obviously raised the temperature at ferrite-1/austenite-1 balance while the Cr and Mo decreased the dual-phase balance temperature.In addition,the Ni addition can promote the precipitating ofσphase at relatively high temperature while the precipitating of Hcp phase at relatively low temperature.The Hcp phase andχphase can be obviously increased by the N addition.The introduction of Cr and Mo notably enhances the precipitation ofσphase.However,the promotion ofχphase precipitation is facilitated by the presence of Mo,while the Cr element acts as an inhibitor forχphase precipitation.Furthermore,the ferrite/austenite ratio tested by experiment was higher than that calculated by thermochemical methods,thus pre-designed solution temperature should be lower about 30-100℃than that calculated by thermochemical methods.

High throughput screening of localised and general corrosion in type 2205 duplex stainless steel at ambient temperature

Bipolar electrochemistry is used to produce a linear potential gradient across a bipolar electrode(BPE),providing direct access to the anodic and cathodic reactions under a wide range of applied potentials.The occurrence of pitting corrosion,crevice corrosion,and general corrosion on type 2205 duplex stainless steel(DSS 2205)BPE has been observed at room temperature.The critical pit depth of 10-20μm with a55%-75% probability of pits developing into stable pits at potential from+0.9 to+1.2 V vs.OCP(open circuit potential)are measured.All pit nucleation sites are either within ferritic grains or at the interface between austenite and ferrite.The critical conditions for pitting and crevice corrosion are discussed with Epit(critical pitting potential)and Ecre(critical crevice potential)decreasing from 0.87 and 0.80 V vs.OCP after150 s of exposure to 0.84 and 0.76 V vs.OCP after 900 s of exposure,respectively.Pit growth kinetics under different applied bipolar potentials and exposure times have been obtained.The ferrite is shown to be more susceptible to general dissolution.

Literature Review of Phase Transformations and Cavitation Erosion of Duplex Stainless Steels

Phase transformation is one of the factors that would significantly influence the ability to resist cavitation erosion of stainless steels. Due to the specific properties of duplex stainless steel, the heat treatment would bring about significant phase transformations. In this paper, we have examined the previous studies on the phase transition of stainless steel, including the literature on the classification of stainless steel, spinodal decomposition, sigma phase transformation, and cavitation erosion of double stainless steel. Through these literature investigations, the destruction of cavitation erosion on duplex stainless steel can be clearly known, and the causes of failure of duplex stainless steel in seawater can be clarified, thus providing a theoretical basis for subsequent scientific research. And the review is about to help assess the possibility of using bulk heat treatment to improve the cavitation erosion (CE) behaviour of the duplex stainless steel 7MoPLUS.

Deformation Mechanism of Bimodal Structured 2205 Duplex Stainless Steel in Two Yield Stages

A kind of micro/nanostructured 2205 duplex stainless steel(DSS)with uniform distribution of nanocrystals was prepared via aluminothermic reaction method.The analysis of stress-strain curve showed that the fracture strength and elongation of the specimen were 946 MPa and 24.7%,respectively.At present,the research on microstructure of bimodal 2205 DSS at room temperature(RT)mainly depended on scanning electron microscope(SEM)observation after loading experiments.The test result indicates that there are two different yield stages in stress-strain curve of specimen during tensile process.The microstructure of duplex bimodal structured stainless steel consists of two pairs of soft hard regions and phases.By studying deformation mechanism of bimodal structured stainless steel,the interaction between soft phase and hard phase are discussed.The principle of composition design and microstructure control of typical duplex stainless steel is obtained,which provides an important research basis for designing of advanced duplex stainless steel.

In Band Full Duplex (IBFD) Technology for Next Generation Wireless Networks: A Survey in Cellular Networks

Next-Generation(NextG)wireless communication networks with their widespread applications require high data rates,seamless connectivity and high quality of service(QoS).To cope up with an unprecedented rise of data hungry applications,users demand more spectral resources imposing a limitation on available wireless spectrum.One of the potential solutions to address the spectrum scarce issue is to incorporate in band full duplex(IBFD)or full duplex(FD)paradigm in next generation networks including 5G new radio(NR).Recently,FD has gained the research interest in cellular networks for its potential to double the wireless link capacity and enhancing spectral efficiency(SE).In half duplex(HD)cellular networks,base stations(BSs)can either perform uplink(UL)or downlink(DL)transmission at a particular time instant leading to reduced throughput levels.Due to the advancement in the self interference reduction(SIR)techniques,full duplex base stations(FD-BSs)can be employed to allow simultaneous UL and DL transmissions at the same time–frequency resources as compared to its HD counterpart.It ideally achieves twice the throughput without any additional complexity at user-equipment(UE).This paper covers a detailed survey on FD cellular networks.A series of SIR approaches,UE-UE mitigation techniques are summarized.Various existing MAC protocols and antenna architectures for FD cellular networks are outlined.An overview of security aspects for FD in cellular networks is also presented.Lastly,various open issues and possible research directions are brought up for FD cellular networks.

二甲苯异构体吸附分离研究进展

二甲苯异构体的分离与纯化是石油化学工业的重要过程之一,但二甲苯异构体的结构和性质极其接近,常规精馏和深冷结晶法分离能耗高、生产效率低。模拟移动床色谱是主流的二甲苯异构体分离技术,但作为吸附剂的分子筛在吸附容量和分离选择性两方面均存在不足。金属有机框架和超分子材料具有组装自由、结构多样和性质可调等优点,可通过构建极性孔环境或精准设计孔道尺寸与形状实现二甲苯异构体的高效辨识与分离。本文综述了金属有机框架和超分子材料在二甲苯异构体吸附分离中的研究进展,从静电作用、尺寸筛分和形状筛分等方面探讨了二甲苯异构体分离的内在机制,总结了金属有机框架在二甲苯分离领域存在的问题和局限,并对未来发展方向进行了展望。

ABO血型变异的分子基础研究

目的 对临床ABO血型变异标本进行ABO亚型、类孟买血型与基因型关联性研究,以探讨这2种血型产生的可能分子背景,为ABO血型的准确鉴定与预判提供精确的基因检测靶点和理论依据。方法 对2022年2—12月瑞金医院2.42万名血型鉴定患者,以及期间来自外院送检10例ABO疑难标本(疑似ABO亚型3例,疑似类孟买血型7例)进行血清学分析,对血清学鉴定为ABO亚型、类孟买血型的行DNA直接测序或克隆后测序分析ABO、FUT1、FUT2基因序列。结果 在共计2.42万血型鉴定患者中检出7例ABO亚型;外院送检的10例疑难标本检出2例ABO亚型、1例正常A型、7例类孟买血型。我们共鉴定出:1)9例ABO亚型,表型及其对应基因型分别为:1例A_(el)(AEL.02/O.01.02)、1例A_(el)B(AEL.05/B.01)、3例B_(3)(2例B3.03/O.01.01、1例B3.03/O.01.02)、1例B(A)(BA.02/O.01.01)、1例AB_(weak)(A1.02/BW.07)、1例B_(weak)(BW.31/O.01.02)、1例A_(2)B_(weak)(A2.05/BW.31);2)7例类孟买血型,表型及其对应基因型分别为:1例AB_(m)^(h)(FUT1^(*)01N.13/FUT1^(*)01N.13)、4例A_(m)^(h)(3例FUT1^(*)01N.06/FUT1^(*)01N.13、1例FUT1^(*)01N.13/FUT1^(*)01N.13)、2例B_(m)^(h)(FUT1^(*)01N.06/FUT1^(*)01N.06、FUT1^(*)01N.06/FUT1^(*)01N.13),7例类孟买的FUT2基因型均为FUT2^(*)01/FUT2^(*)01。结论 ABO血型变异标本需联合血清学与分子生物学方法进行鉴定,方能提高对血型变异标本的鉴定准确率,从而为临床安全输血、器官移植、胎母免疫性溶血病的预测与防治提供参考。

芳纶纤维的发展现状及应用

总结了芳纶纤维的性能、改性研究、染色印花性能研究发展现状,以及芳纶纤维在金属化、体育运动、柔性防刺防弹材料、航空航天材料等的应用及研究情况。

基于改进涡流搜索算法的外骨骼迭代学习控制

为提升康复外骨骼机器人的步态跟踪性能,提出一种基于改进涡流搜索算法的迭代学习控制方法。首先针对传统迭代学习控制抗扰性差和控制信息缺失问题,引入PD控制器、自适应遗忘因子、误差过渡曲线和控制信息搜索等策略,改进迭代学习控制律;其次,基于多种策略对涡流搜索算法进行改进,提出了一种改进涡流搜索算法,改进后的算法可优化迭代学习控制的PD参数;最后进行行走实验,将提出的迭代学习控制方法与现有的同类算法进行仿真和数值比较,并测试了扰动情况下的跟踪性能。实验结果表明,所提方法的误差更小,跟踪性能更强。该算法改进了迭代学习控制的不足,具有较强的抗扰性能,保证了使用时的稳定性。

空中可重构智能表面辅助的全双工无人机安全通信

针对传统的可重构智能表面(reconfigurable intelligent surface,RIS,也称智能超表面)在无人机辅助安全通信中存在的灵活性不足和系统安全保障能力不强的问题,以及当前无人机半双工通信系统普遍面临的频谱利用率低和通信效率低的挑战,提出了一种空中可重构智能表面(aerial reconfigurable intelligent sur‐face,ARIS)与全双工无人机的双机协同解决方案,旨在提升面对地面窃听者时的通信安全性和效率。联合优化用户通信调度、传输功率、无人机发送的干扰功率及其飞行轨迹,以及ARIS的相移和轨迹,设计了一个旨在最大化最小平均可达安全速率的优化问题,并提出基于交替优化(alternating optimization,AO)、半定松弛(semi-definite relaxation,SDR)技术和连续凸近似(successive convex approximation,SCA)的迭代算法,以获得高质量的次优解。仿真结果验证了ARIS与全双工无人机结合的双机协作方案在提升通信质量和安全性能方面的有效性,展示了其在复杂安全通信环境下的优越性。

IRS辅助的全双工通感一体化波束成形设计

为了解决传统通感一体化(integrated sensing and communication,ISAC)场景中通信和感知系统收发信号的切换频率差异以及通信易受障碍物阻挡的问题,将全双工(full-duplex,FD)技术和智能反射面(intelligent reflecting surface,IRS)引入ISAC系统,研究ISAC场景下IRS辅助的FD波束成形设计。基于IRS相移约束、基站接收波束成形约束、基站最大发射功率约束、上行用户最大发射功率约束、雷达感知阈值约束,建立了上下行用户和速率最大化波束成形优化问题。利用交替优化、连续凸逼近、半正定松弛、变量替换、半正定规划将原非凸优化问题转换成凸优化问题进行求解。仿真结果表明,在所考虑的通信性能指标下,所提方案相比对应的半双工和随机IRS方案分别提升了89.02%和70.15%。

鉴别猪圆环病毒2型和3型双重TaqMan MGB探针FQ-PCR检测方法研究

建立一种快速、特异鉴别检测猪圆环病毒2型(PCV2)和猪圆环病毒3型(PCV3)的双重TaqMan MGB探针FQ-PCR方法,本研究以PCV2的Rep蛋白和PCV3的Cap蛋白基因作为靶基因,各设计1对特异性引物和1条TaqMan MGB探针,经优化各反应条件和进行敏感性、特异性、重复性和干扰性试验,建立鉴别检测PCV2/PCV3的双重FQ-PCR方法。结果显示:该方法可特异性扩增PCV2、PCV3核酸,与猪伪狂犬病病毒(PRV)等8种病原及阴性对照无交叉反应,特异性较强;对PCV2和PCV3阳性质粒标准品的最低检出限均可达10 copies/μL,敏感性较高;PCV2/PCV3批内/批间重复试验变异系数(CV)值均在3%以下,表明方法稳定性、重复性较好;干扰性试验表明在两种病毒阳性质粒起始模板相差较大时该方法不会影响对其中任一病毒核酸的检出和准确定量。对42份临床疑似PCV感染样品检测结果与PCV2、PCV3基因测序结果符合率100%。本研究建立的双重FQ-PCR方法具有敏感性高达10 copies/μL、特异性强、在同一反应体系中能同时快速鉴别检测PCV2、PCV3等优点,可用于临床PCV2/PCV3感染的快速鉴别检测。

不同强度级别双相不锈钢激光焊接头的组织与力学性能

目的为了合理制定不同强度等级DP钢同种和异种接头的激光焊接工艺,研究激光焊接工艺对接头组织性能的影响。方法采用SEM、硬度试验、拉伸试验等手段,研究不同强度等级DP钢同种和异种激光焊接接头的微观组织和力学性能。结果对于同种DP钢激光焊接,由于接头各个区域经历的热循环不同,因此其马氏体体积分数和形态、含碳量等存在明显差异。在焊缝熔合区,由于冷却速度较高,因此马氏体体积分数较高且为细条状,硬度高于母材硬度。在热影响区,由于马氏体发生了回火分解,因此其硬度值低于母材硬度,且软化的程度和范围大小与DP钢的强度级别相关。软化的热影响区成为接头的薄弱区域,降低了接头的拉伸性能。在异种DP钢激光焊接接头中,焊缝熔合区的硬度也明显高于母材硬度。靠近高强度级别母材侧的热影响区范围更大,软化程度更明显,接头硬度分布不再对称。接头的抗拉强度与低等级DP钢母材的抗拉强度基本一致。结论激光焊接工艺对不同强度等级DP钢同种和异种接头组织性能的影响存在较大的差异,DP钢强度级别越高,接头或接头对应侧的热影响区软化程度越明显,这在制定焊接工艺以及焊后处理工艺过程中需要予以考虑。