铍材表层应力梯度对X射线应力测试的影响

研究了在modified-ψ衍射几何条件下，铍材表层中存在不同应力梯度时的d-sin^2ψ曲线的形状，确定了铍材表层内的应力梯度对常规的X射线应力测试的影响，结果表明：在通常的sin^2ψ≤0．5的应力测试范围内，应力梯度对测试曲线有明显的影响，应力测试值因应力梯度的存在而偏离真实值，选择合适的靶材以减小X射线对铍材的穿透深度，可以减小应力测试的误差。     

工程陶瓷磨削表面残余应力的测量新方法

磨削加工后工程陶瓷零件表面会产生残余应力。X射线衍射法是用来测量磨削加工后工程陶瓷中残余应力的可靠测量手段。传统的X射线衍射法称之为sin^2ψ法，通常只能测量工件表层的残余应力；本文介绍了一种残余应力测量新方法，该方法联合使用sin^2ψ法和掠入射X射线衍射法从而得到残余应力在试件中的深度分布。如果考虑X射线的折射，在一系列掠射角下采集到的X射线衍射花样的有效穿透深度和衍射角必须进行折射校正。最后，用这种方法得到的残余应力值是X射线照射的所有层的平均值。     

基于SWRXD的5083/6082异种铝合金搅拌摩擦焊接头的残余应力分布规律

以5083铝与6082铝为研究对象,利用搅拌摩擦焊（friction stir welding,FSW）制备了异种材料对接接头.利用短波长X射线衍射（short-wavelength X-ray diffraction,SWRXD）技术,以{311}与{111}为衍射晶面,基于极图最外圈织构参量确定了残余应力测试方向,采用d₀法研究了FSW焊件中心层的残余应力.结果表明,{111}和{311}晶面测试的纵向残余应力分布趋势相近,焊核区为拉应力并出现两个应力峰值;{111}晶面的测试结果更为离散,应力的峰值向前进侧偏移;采用{111}晶面测试的横向的残余应力分布趋势与{311}晶面测试的结果偏差较大.     

压缩变形对Ti1023合金应力诱发马氏体晶体结构的影响(英文)

对Ti1023钛合金在不同压缩量变形应力诱发马氏体晶面衍射峰位呈现明显规律性变化的现象,及其晶面取向规律进行了研究。结果表明:不同压缩变形量条件下应力诱发马氏体晶格参数发生变化,随着压缩形变量增大,晶胞常数a减小、b增加、c呈波动变化,导致X射线晶面衍射峰位产生明显的变化。在压缩变形条件下,应力诱发马氏体晶面取向产生明显变化,呈现(020)和(021)晶面的择优取向。     

Effect of Compressing Deformation on the Crystal Structure of Stress-Induced Martensitic in Ti-10V-2Fe-3Al Titanium Alloy

对Ti1023钛合金在不同压缩量变形应力诱发马氏体晶面衍射峰位呈现明显规律性变化的现象,及其晶面取向规律进行了研究。结果表明:不同压缩变形量条件下应力诱发马氏体晶格参数发生变化,随着压缩形变量增大,晶胞常数a减小、b增加、c呈波动变化,导致X射线晶面衍射峰位产生明显的变化。在压缩变形条件下,应力诱发马氏体晶面取向产生明显变化,呈现(020)和(021)晶面的择优取向。     

利用半高宽分析铝合金X射线法应力测试工艺

文中采用X射线法测试6061-T6铝合金焊接接头残余应力,为探究合理的应力测试工艺方案,对预置应力的等强梁进行X射线应力测试,测试过程中先后增加准直器直径和摇摆角,以衍射曲线半高宽表征衍射晶粒群微观应变,研究在准直器直径和摇摆角增加时衍射晶粒群微观应变均匀性的变化,对材料进行取向成像分析,并对比在晶粒择优取向强弱不同的两个区间内应力测试的结果. 结果表明,应力测试精度与晶粒择优取向的强弱相关,在晶粒择优取向较强的空间范围内,采用大于1°的摇摆角时,小角度晶界附近的相邻亚晶都能够参与衍射,从而使衍射晶粒群微观应变趋于均匀,因此X射线应力测试精度较高,在d = 2 ~ 4 mm范围内,增加准直器直径d可增加衍射晶粒数目,但对衍射晶粒群微观应变均匀性及应力测试精度的影响不大.     

钛及钛合金X射线应力测试参数的选择

针对钛及钛合金X射线应力测试中衍射峰强度低、峰形差、测试结果波动范围大和准确度低等问题,通过对标准零应力试样和标准应力试样的X射线应力测试,研究了钛及钛合金X射线应力测试中准直器直径、计数时间和计数次数变化对衍射峰强度、净峰强度、半高宽、应力测试结果的影响规律,在此基础上确定了钛及钛合金X射线应力测试参数的选择方法,并对钛合金电子束焊接头的残余应力进行了测试.结果表明,随着准直器直径增大和计数时间增长,衍射峰强度增大,衍射峰形改善,测试结果准确性提高;随着计数次数增加,衍射峰形改善,测试结果准确性提高;所确定的测试参数对钛合金电子束焊接头残余应力测试的结果满足相关标准要求.     

单晶结构残余应力的X射线衍射分析技术

准确测定单晶材料残余应力是控制和调整单晶构件中残余应力的前提。基于弹性力学对单晶材料弹性模量与对应衍射晶面的关系进行理论分析,建立立方单晶材料的残余应力分析模型,并提出具体试验方法,以DD3单晶叶片为例,进行试验验证。结果表明：不同衍射晶面的弹性模量受独立弹性柔度系数、取向系数影响,DD3单晶叶片表面应力模型计算值与实测值间相对误差在20 MPa范围内。这种X射线衍射残余应力测定方法测定的残余应力值可靠性较高,为工程应用中测定立方单晶残余应力提供了理论依据和试验基础。     

焊接结构残余应力的X射线衍射测试及分析

介绍了X射线衍射测试残余应力的原理和测试技术,采用X射线衍射方法对大型焊接结构组装态、焊态、去应力热处理态的残余应力进行了测试,分析了组装工艺、焊接工艺等对残余应力分布的影响.为大型焊接结构组装和焊接工艺的合理制定提供支持.     

残余应力及其分布的X射线二维衍射分析与计算

根据在X射线二维衍射几何关系下建立的应力应变基本方程,提出了一种基于X射线多晶面探测器衍射系统的残余应力及其分布测量方法,即通过分析X射线衍射圆锥的变形程度确定应变张量,进而计算应力张量。该方法有效地利用X射线面探测器的“虚拟摆动”功能,在一定程度上解决了传统X射线衍射法较难处理的粗晶材料和有织构材料的残余应力测量问题。对304不锈钢的残余应力及其分布进行了分析与计算,结果表明,该合金呈表面残余压应力,并且应力分布比较均匀。     

铍材中子衍射应力测试的参数及其优化

利用铍环焊接样品进行了铍材在稳态堆上中子衍射应力测试的参数及其优化研究。结果表明:在中子束波长0.1587 nm和中子注量率2×10~6 n·cm~(-2)·s~(-1)的条件下,铍材中子衍射应力测试可以选取Be(110)晶面,衍射角为88.2°,规范体积为2 mm×2 mm×2 mm,初次测试采用时间为120 s,对单点进行4次重复性测试,表明衍射强度计数存在明显波动,测试应变的最大偏差接近300με,延长时间至6000 s后测试,表明衍射曲线较为平滑,重复性好,测试应变的最大偏差减小至50με以内,相应铍材的应力测试精度约15 MPa;利用优化参数对焊接铍环焊缝附近的环向应变进行了测试,表明分布规律与国外文献报道趋势基本一致,进一步开展铍材的中子衍射应力测试奠定了基础。     

紧凑拉伸Be试样应力和断裂行为研究

利用X射线应力分析仪和在线加载装置测试了紧凑拉伸(compacttension,CT)Be试样缺口前端的应力分布,利用万能拉伸试验机、引伸计和扫描电镜研究了紧凑拉伸Be试样的断裂行为.研究表明:样品加工缺陷如缺口在载荷作用下形成应力集中,样品首先在此开裂,获得了紧凑拉伸铍试样的载荷-裂纹张开曲线和平面应变断裂韧性为15.4MPa√m.扫描电镜观察表明Be断口呈现解理特征,紧凑拉伸试样断口呈现出3个特征区.裂纹尖端扩展观察表明沿基滑移面形成解理微裂纹,这些微裂纹长大后受主应力控制.利用断裂韧性评估了Be材存在微裂纹时的断裂强度.     

热时间常数在QBe2箔与Cr20Ni80丝电容储能点焊中的应用

为了满足微型电机电刷零部件的使用要求,根据计算所得的热时间常数τ及其与焊点中心部分温度上升的关系曲线,确定了QBe2铍青铜箔与Cr20Ni80镍铬丝微型件电容储能点焊工艺参数的选取原则.根据所选的工艺参数,采用电容储能点焊机对试样进行焊接,并对焊接接头的金相组织、微区成分进行了分析试验.结果表明,利用热时间常数选取的工...     

QBe2铍青铜与Cr20Ni80镍铬丝的微型件电容储能点焊

阐述了在微型电机电刷零部件的生产过程中,铍青铜与镍铬丝电容储能点焊的工艺过程,分析了微型件点焊的特殊性,计算了微型件的热时间常数τ,且根据选择的规范参数及焊接电流波形,提出了τ及电流上升时间之间的一些对应关系,并对焊接接头的金相组织,元素扩散以及力学性能进行了分析试验.发现采用电容储能点焊机对QBe2铍青铜与Cr20Ni80镍铬丝微型件进行焊接可以获得良好的焊接接头,焊接界面铍青铜一侧有晶界局部熔化现象,焊点的抗拉强度为375MPa,镍铬合金中的镍元素与铬元素有向铍青铜中扩散的现象.     

Experimental approach of a crystallographic cleavage criterion in a cast aged duplex stainless steel

The stress state distribution in an aged duplex steel is determined in each phase and is then correlated to local damage mechanisms. The measurements are performed at the grain scale because the studied material contains coarse grains up to one millimetre in size. A single-crystal specific X-ray method is required to determine the stress tensor. During in situ loading, the mechanical state determined in the ferritic crystal is associated with both the plastic flow and the damage mechanism observation. The coupling of the techniques makes it possible to establish that for the studied aged material, the stress normal to a {100} plane value of 465 MPa can be considered as a crystallographic criterion for cleavage propagation. The comparison of this value with the Cottrell's model seems to be good but the number of dislocations in the pile-up must be verified experimentally.     

Plasma-Sprayed Beryllium on Macro-Roughened Substrates for Fusion Reactor High Heat Flux Applications

The development of beryllium first wall (FW) plasma facing components for future magnetic confinement fusion experiments, such as the International Thermonuclear Experimental Reactor (ITER), is a topic of great importance as research into long-term energy sources increases in urgency. The FW components must be able to survive the harsh plasma environment for extended periods of time. One proposed method for initial fabrication and repair of FW components is plasma spraying. Previous plasma-sprayed beryllium mock-up FW components had coating separation from the substrate at the edges. The present work describes experiments to produce beryllium mock-up FW components by plasma spray deposition on macro-roughened substrates. Experimental parameters, high heat flux testing and characterization results from the components are presented. No separation of the coating from the substrate was observed. Results of high heat flux testing under electron beam irradiation show performance exceeding that required for ITER FW components. Differences in macro-roughening features result in changes in the threshold absorbed heat flux before damage to the coatings occurs.     

铍青铜用于模具的失效成因与对策

对铍青铜在电子元器件封焊模具、压铸模头及精密注塑模方面应用失效的原因进行了研究,提出相应的对策;通过对熔炼工艺、热加工工艺等关键生产工艺严格控制,并用光谱分析对铸锭化学成分进行分析,调整合金成分,以保证成分在合格范围之内,使高性能铍青铜主要性能达到同类进口产品的水平.     

Beryllium Extracted by the Fluoride Process

The steps used in producing high-purity BeO and beryllium metal, including recent modifications to production processes, are described. Particular emphasis is placed on the fluoride extraction process in which beryllium is attacked preferentially, and beryllium oxide is converted into a water-soluble form of beryllium fluoride so that no additional chemicals are required to react with other materials present in beryl ores.Beryllium is processed from the ore in four major steps: (1) the beryl ore is converted into a standard grade of beryllium hydroxide, (2) the hydroxide is purified, (3) purified beryllium hydroxide is reacted with ammonium bifluoride for conversion into ammonium beryllium fluoride, and (4) then reduced to beryllium metal.The fluoride process is attractive economically and offers an additional advantage of versatility.     

Stress corrosion failure of Zircaloy-2 sheets in methanolic HCl solution: Role of crystallographic texture

The stress corrosion cracking (SCC) characteristics of Zircaloy-2 sheets in methanol-0.4 vol. pct. hydrochloric acid have been studied in the annealed and cold-rolled conditions using longitudinal and transverse specimens. The times to failure for annealed longitudinal specimens were longer than those for similarly tested transverse specimens at stress levels below ～45% UTS. The cold-rolled specimens developed resistance to SCC, but failed totally by cleavage when notched, unlike annealed specimens which failed by intergranular initiation followed by cleavage. The crystallographic texture developed by cold rolling is such that the crack initiation is difficult because of quicker passivation characteristics of the crack initiating plane. The texture also gives unfavourable orientation of slip and twinning planes with respect to tensile axis. The crack initiating planes are identified with the help of X-ray pole figures. The apparent activation energy is found to be texture dependent at a given stress level. On the basis of apparent activation energy measurements, dynamic tests at constant cross-head speeds and electrochemical measurements, the mechanism of SCC is identified to be the one involving stress-aided anodic dissolution.     

低温时效对铍材尺寸稳定性的影响

利用拉曼光谱仪、纳米压痕仪、电子背散射衍射电镜以及透射电镜分析低温时效后等静压铍材的残余应力、晶粒取向差、位错密度及位错分布形态,分析低温时效处理对铍材尺寸稳定性的影响。结果表明,低温时效处理后,热等静压铍材、退火铍材和热冷循环铍材在热循环过程中的尺寸收缩均明显减小。低温时效处理过程中铍材尺寸稳定化机制主要是晶粒内位错均匀化及微塑性变形导致取向差均匀化。