Flow stress and softening behavior of wrought magnesium alloy AZ31B at elevated temperature

1　INTRODUCTIONThewroughtmagnesiumalloyshaveexcellentspecificstrengthandstiffness ,machinability ,dampcapacity ,dimensionalstability ,lowmeltingcostsandare ,hence ,veryattractiveinsuchapplicationsasau tomobile ,aviation ,electronicandcommunicationin dustry[16 ] .Investigationsontheflowstressandsofteningbehaviorofmagnesiumalloysathigherformingtem peratureandstrainratehavebeenanimportantsub jectinwroughtmagnesiumalloysforming[710 ] .InthispapertheflowstressandsofteningbehaviorofAZ31Bdeform…     

Multidisciplinary optimization of gas-quenching process

Distortion as a result of the quenching process is predominantly due to the thermal gradient and phase transformations within the component. Compared with traditional liquid quenching, the thermal boundary conditions during gas quenching are relatively simple to control. By adjusting the gas-quenching furnace pressure, the flow speed, or the spray nozzle configuration, the heat-transfer coefficients can be designed in terms of both the component geometry and the quenching time. The purpose of this research is to apply the optimization methodology to design the gas-quenching process. The design objective is to minimize the distortion caused by quenching. Constraints on the average surface hardness, and its distribution and residual stress are imposed. The heat-transfer coefficients are used as design variables. DEFORM-HT is used to predict material response during quenching. The response surface method is used to obtain the analytical models of the objective function and constraints in terms of the design variables. Once the response surfaces of the objective and constraints are obtained, they are used to search for the optimum heat-transfer coefficients. This process is then used instead of the finite-element analysis. A one-gear blank case study is used to demonstrate the optimization scheme.     

划痕法测Ni—P合金镀层结合力的研究

本文用划痕法测定了Ni-P合金镀层的结合力;观察了划痕侧面镀层的失效形式;分析了三种评定结合力的参数。结果指出,临界载荷L_C、平均应力σ_A用于评定Ni-P镀层的结合力是有条件的,而B-W公式存在的问题更多。     

Stress relaxation behavior of Ti-6Al-4V alloy

1　INTRODUCTIONTi 6Al 4VisoneofthemostimportantTial loys[1,2 ] .Butthisalloyhasbadformabilityforitshighelasticresilience .Therefore ,hotsizingisimpor tant[36 ] .Asthebaseofhotsizing ,thestudyofstressrelaxationhasimportanttheoreticalvalueandpracticalsignificance .Ontheotherhand ,Ti 6Al 4Visusedasfastenermaterialssometimes .Whenthefastenersworkatthetemperaturehigherthanroomtemperature ,stressrelaxationmayresultsinacci dents .Sohowtopreventthestressrelaxationisveryimportant[7] .Uptonow ,…     

Characterization of angular dependence of macroscopic magnetic properties in ASTM 36 steel using magnetic Barkhausen noise

Angular-dependent magnetic Barkhausen noise measurements were performed on ASTM 36 steel samples for various values of applied uniaxial stress. The maximum differential permeability and the coercive field are obtained from this Barkhausen signals. The angular dependence of these macroscopic magnetic properties is studied. The tension for which the magneto-elastic energy balances the anisotropic energy is estimated. The results are discussed based on the domain wall theory.     

强流脉冲离子束表面再制造技术原理与应用

采用TEMP-6型强流脉冲离子束(HIPIB)装置开展了HIPIB表面再制造技术的研发.HIPIB装置主体由高压脉冲电源系统和高功率离子二极管系统组成,通过高压短脉冲在二极管中放电产生阳极等离子体并引出ns级强流离子束.HIPIB辐照材料表面,发生显著的熔融、蒸发和剧烈烧蚀,物质喷射的反冲作用在辐照表面形成由表及里的应力波,导致材料表层强烈的热-力学效应.利用HIPIB与材料表面的相互作用,应用于涡轮叶片表面的清洗维修,可有效去除涡轮叶片基体因高温氧化形成的氧化物,伴随表层的重熔将叶片基体表面微观缺陷焊合,获得了光滑、平整的涡轮叶片修复表面.实现了HIPIB辐照在涡轮叶片表面再制造方面的应用.     

一种Cr—Mn—Mo—B低碳低合金钢的热变形行为

利用ＴＨＥＲＭＣＭＡＳＴＯＲ－Ｚ热处理机对一种Ｃｒ－Ｍｎ－Ｍｏ－Ｂ钢的热变形行为进行了研究，绘制了真应力－应变曲线，得到了各变形工艺参数之间的定量关系，得出试验用钢的Ｑ值为３７３．７ｋｊ／ｍｏｌ。在此基础上给出了试验用钢的动态再结晶图，试验发现，试验用钢９００℃以上变形后，在奥氏体区冷过程中发生静态再结晶与晶粒长大，相变前晶粒尺寸与变形条件Ｚ的关系：ｄｒｅｃ＝２．８８×１０＾４×Ｚ＾－０．２０５。     

应力松驰与非晶态Fe_（79）B_（16）Si_5合金磁性优化

分析了退火过程中应力的松驰与作晶态合金磁性优化之间的联系淬态Ｆｅ_（７９）Ｂ_（１６）Ｓｉ_５非晶合金经退火后，饱和磁感应强度Ｂ、提高了７２％，最大磁导率μ_ｍ提高２２倍，矫顽力Ｈ_ｃ和功率损耗Ｐ（０．３Ｔ，１０ｋＨｚ）分别降低８６％和８３％。退火过程中条带内应力的松驰，有效地去除了应力感生磁各向异性，使非晶态合金的磁性得到显著优化。     

STUDY ON THE TENSILE FATIGUE DAMAGE OF QUASI—ISOTROPIC COMPOSITE LAMINATES

Quasi-isotropic. laminates have isotropic elastic properties in all in-plane directions. Therefore, this kind of laminate is widely used for structural elements. The simplest stacking sequence of quasi-isotropic laminates is [0/-60/60]s. When the direction of applied axial load to [0/-60/60]s laminate is inclined at a 30-degree angle, we have the other quasi-isotropic laminate [30/-30/90]s under axial load. The failure mechanisms of these two laminates are, however, entirely different from each other because these two laminates have different distribution of the interlaminar stresses. It was confirmed by tensile fatigue tests that the [0/-60/60]s laminate does not show any visible fatigue damage, but the [30/-30/90]s laminate develops edge-delamination during cyclic loading. The analytical results were in good agreement with the experimental results.     

EFFECT OF RESIDUAL STRESS ON THE MARTENSITIC TRANSFORMATION OF SPUTTER-DEPOSITED SMA THIN FILMS

TiNi thin films were sputter-deposited on circular single-cry stal silicon substrates un-der various sputtering parameters. The crystal structure and residual stress of the as-deposited films were determined by X-ray diffraction and substrate-curvature method. The phenomenon of stress-suppressed martensitic transformation was observed. R is considered that the residual stresses in SMA thin films based on circular substrates act as balanced biaxial tensile stresses. The status of equilibrant delays the align-ment of self-accommodated variants and the volume shrinkage during the martensitic transformation.