9Cr-1Mo-V-Nb-N钢高温变形规律的研究

利用Ｇｌｅｅｂｌｅ－１５００热模拟试验机,研究了９Ｃｒ－１Ｍｏ－Ｖ－Ｎｂ－Ｎ铁素体耐热钢在８５０～１２５０℃,变形速率０．０１～１０ｓ－１的变形条件下的再结晶行为。获得了９Ｃｒ－１Ｍｏ－Ｖ－Ｎｂ－Ｎ钢热变形时发生动态再结晶的边界条件,作出了塑性图和再结晶图。     

86CrMoV7钢热变形奥氏体CCT图

采用膨胀法测定了８６ＣｒＭｏＶ７钢经Ｔ＝９００℃，ζ＝１ｓ＾－１，ε＝０．４热变形后的连续冷却变曲线。结果表明，试验用钢在连续冷却转变过程中，只存在珠光体，马氏体转变，不发生珠光体转变的临办冷却速度为３．１℃／ｓ，Ｍｓ点为１５０℃，组织分析发现，未溶碳化物可成为珠光体转变的核心，促进珠光体转变。     

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。     

铸造—热压PrFeB系永磁合金的热变形与磁性能

研究了Ｐｒ１７Ｆｅ７６．５Ｃｕ１．５Ｂ５永磁合金的热压变形与磁参量。诸如μ０Ｍｓ，Ｂｒ，ｉＨｃ和（Ｂ．Ｈ）ｍ等的相互依赖关系。根据Ｐｒ－Ｆｅ－Ｂ相关系和Ｍｓ与成分的依赖关系计算了μφＭｓ与变形量的关系。根据Ｐｒ２ＦＥ１４Ｂ相晶体结构的特点与热变形原理导出了平行取向因子（ｃｏｓθ＾－）ｐ和垂直取向因子（ｃｏｓθ＾－）ｖ与变形量关系的表达式，并对这些结果作了讨论。     

刃口硬度检测

制作了６５Ｍｎ钢和４５钢刃口标样，通过比较洛氏硬度ＨＲＣ与刃口硬度Ｈθｓ的检测数据，证实了只在改变洛氏硬度计的金刚石头和施加的负荷，就可测出刃口硬度Ｈθｓ。根据实数据的处理，得出经验公式ＨＲＣ＝０．５０１８Ｈθｓ＋３５．８３，很容易将所测数据Ｈθｓ换算成ＨＲＣ，绝对误差在－０．６５－０．４７ＨＲＣ之间。     

热变形及冷却条件对0.1%C—2%Si多双相组织形成的影响

研究了热变形及冷却条件对０．１％Ｃ－２％Ｓｉ钢双相组织形成的影响。结果表明：终轧温度与冷却速度影响钢的双相组织形成及最终马氏体与铁素体双相组织相对量;通过控轧、控冷,控冷,０．１％Ｃ－２％Ｓｉ钢可获得理想的铁素体加～２０％马氏体热轧双相组织。     

GCr15钢高速热变形与再结晶的研究

利用Ｆｏｒｍａｓｔｏｒ－Ｐｒｅｓｓ热模拟试验机对ＧＣｒ１５钢高速热变形及再结晶过程进行了研究，着重探讨了形变速率及间隔时间对变形与再结晶过程的影响。结果表明：Ｌ在高速变形条件下，随着变形速率的增加，形变享晶数量逐渐增加，同时，形变速率的增加促进了动再结晶过程的进行，改善了再结晶后组织的均匀性。在高形变速率、小变形量、多次变形时，当各道次各间隔时间很短时（＜ｌｓ），真应力－真应变曲线接近于平滑。     

PCrNi3MoVA钢动态再结晶晶粒尺寸的影响因素

此文利用Ｆｏｒｍａｓｔｏｒ－Ｐｒｅｓｓ热模拟试验机研究了Ｚ参数，奥氏体起始晶粒尺寸Ｄ０和应变ε对ＰＣｒＮｉ３０ＭｏＶＡ钢动态再结晶晶粒尺寸Ｄｄｙｍ的影响。     

H62黄铜超塑性压缩变形的力学特性

通过压缩试验，研究了供应态Ｈ６２黄铜棒材的表现出的超塑性变形的力学特性。在温度６５０－８００℃，卡头速度０．００４６－０．５３７ｍｍ／ｓ范围内，在４ｔ载荷下可获得最大真应变εｍａｘ在２．３以上，当变形温度为７００℃，卡头速度为０．００４６ｍｍ／ｓ时，εｍａｘ可达２．９１，流动应力为０．８０ＭＰａ。金相显微组织观察表明变形过程中发生动态再结晶。     

34CrNi3Mo钢高温变形行为与Zener—Hollomon因子的关系

通过热模拟压缩试验，研究了３４ＣｒＮｉ３Ｍｏ合金结构钢在温度８４０￣１２００℃，变形速度０．１￣８０Ｓ＾－１变形条件下的热压缩行为。获得了３４ＣｒＮｉ３Ｍｏ钢的变形激活能及峰值流动应力（σｐ）、发生动态再结晶的临界条件（包括临界因子Ｚｃ和临界应变εｃ）和再结晶晶粒大小（ｄ）与Ｚｅｎｅｒ－Ｈｏｌｌｏｍｏｎ因子Ｚ的关系，并给出了回归公式。     

超细晶工业纯钛的变形、应变速率敏感性和激活体积

在温度为250~450 ℃、应变速率为1×10-4-1 s-1的条件下，对超细晶工业纯钛进行变速率压缩实验，计算超细晶工业纯钛的应变速率敏感性因子和激活体积，并研究超细晶工业纯钛的变形行为。研究结果表明：超细晶工业纯钛在稳态变形阶段存在流变软化效应，这是受变形过程中大角度晶界和位错活动所控制的。超细晶工业纯钛的应变速率敏感性因子和激活体积在数值上都相对较低，应变速率敏感性随着变形温度的升高而增加，但激活体积独立于变形温度。应变速率敏感性和激活体积的数值表明晶粒内部位错之间的交互作用几乎不发生，而位错与晶界之间的交互作用显著影响超细晶工业纯钛的塑性变形。     

120°模具室温ECAP制备工业纯钛的热压缩变形行为

在Gleeble-1500热模拟机上对室温120°模具等径弯曲通道变形(ECAP)制备的平均晶粒尺寸为200nm的工业纯钛(CP-Ti)进行等温变速压缩实验,研究超细晶(UFG)工业纯钛在变形温度为298～673K和应变速率为10-3～100s-1条件下的流变行为。利用透射电子显微镜分析超细晶工业纯钛在不同变形条件下的组织演化规律。结果表明:流变应力在变形初期随应变的增加而增大,出现峰值后逐渐趋于平稳;峰值应力随温度的升高而减小,随应变速率的增大而增大;随变形温度的升高和应变速率的降低,应变速率敏感性指数m增加,晶粒粗化,亚晶尺寸增大,再结晶晶粒数量逐渐增加;超细晶工业纯钛热压缩变形的主要软化机制随变形温度的升高和应变速率的降低由动态回复逐步转变为动态再结晶。     

Uniaxial Tensile and Simple Shear Behavior of Resistance Spot-Welded Dual-Phase Steel Joints

Small test coupons were machined from single spot welds in a dual-phase steel (DP600) to investigate deformation and failure of weld joints in both tension and shear. Quasi-static () testing was conducted in a miniature tensile stage with a custom image acquisition system. Strain accumulation in each weld was analyzed where fracture occurred, which was typically outside the fusion zone. A few shear test coupons that failed in the fusion zone were found to have the same spheroidal defects noted in previous work, and thus, severely limited weld strength and ductility. A novel strain mapping method based upon digital image correlation was employed to generate two-dimensional deformation maps, from which local stress-strain curves to failure were computed. As an important first step toward incorporation of material models into weld simulations, a preliminary finite element analysis of a tension test successfully reproduced the experimental results with material models for the base, heat-affected, and fusion zone materials generated from prior work.     

The mechanics of incremental sheet forming

The deformation mechanism of incremental sheet forming (ISF) is examined experimentally through forming specially prepared copper sheets. Strain distributions through the thickness of the sheets are measured for two configurations of ISF: two-point incremental forming (TPIF) and single-point incremental forming (SPIF), and a comparison is made to pressing. The measurements show that the deformation mechanisms of both SPIF and TPIF are stretching and shear in the plane perpendicular to the tool direction, with shear in the plane parallel to the tool direction. Strain components increase on successive laps, and the most significant component of strain is shear parallel to the tool direction. Increasing stretching and shear perpendicular to the tool direction account for differences between the sine law prediction and measured wall thickness for both SPIF and TPIF. The observed mechanisms of SPIF and TPIF differ from a mechanism of pure shear that has previously been assumed.     

On strain gradients and size-dependent hardening descriptions in crystal plasticity frameworks

Strain gradient crystal plasticity models have been quite successful in describing size-dependent deformation. Various formulations have been suggested in the literature involving approaches that vary considerably in principle. In this respect it is important to associate certain classes of material models to specific deformation mechanisms and to investigate possible inherent restrictions. To this end, the scaling relation between dislocation substructures and the order (first order, second order) of strain gradients in the corresponding continuum formulation are discussed. Conclusions for isotropic and kinematic hardening on slip system level and their related orders in the strain gradients are drawn.     

应变梯度形变理论的无网格数值方法研究

金属材料的微塑性成形过程中,会体现出强烈的尺度效应,应变梯度形变理论能够预测材料尺度效应,但该理论的数值实施需要实现位移函数C1连续,这对传统有限元方法是巨大的挑战。新兴的无网格法能够实现位移函数的高阶导数连续,该文导出了应变梯度理论的无网格数值实施方法,采用发展的数值方法分析了超薄梁弯曲成形过程中的尺度效应,数值结果与理论解相吻合。     

Flow stress and microstructural evolution in as rolled AZ91 alloy during hot deformation

1　INTRODUCTIONMgalloysarethelightestconstructionmaterialsformanyengineeringcomponentsduetotheirlowdensity ,higherductilityandsuitablestrength[13] .However ,Mgalloyshavepoorformabilityandlimit edductilityatroomtemperaturebecauseofitsHCPstructure[4 ] .Therefore ,itisrequiredforMgalloystobedeformedatwarmtemperature(>4 98K ) [5] ,es peciallyatelevatedtemperature ,whenprismaticslipisactivatedsothattheformalityofMgalloyscanbeimprovedintermsofhighductilityandmakesiteasytosimplifythedesignandm…     

Al-3%Si半固态SIMA过程的微观组织演变

对Al-3%Si的SIMA(Strain Induced Melt Activation-应变诱发熔化激活)半固态成形方法的组织演变过程进行了研究,以便为铝合金部件的SIMA半固态成形提供理论指导.研究结果表明:经压缩变形后的Al-3%Si合金在保温过程中的组织经过形状大小不同的多边形晶粒、均匀的粒状组织、球化组织最后演变为粗化颗粒.压缩形变量越大,半固态等温保温后,晶粒平均等积圆直径越小,球化程度越高.但是压缩形变量超过50%后,晶粒等积圆直径变化不大.随着半固态等温保温时间的延长,晶粒平均等积圆直径逐渐增大,圆度呈增加趋势,保温60到90 min时,圆度基本趋于常数.     

切角板坯对纯铜薄板矩形盒拉深影响的试验及数值分析

在大量纯铜薄板矩形盒拉深试验的基础上,结合有限元计算,分析了矩形盒的拉深特性。指出,矩形切角板坯使法兰曲边变形分布得以改善,非拉深变形抵抗弱化,提高了拉深成形性。有限元模拟结果显示矩形板坯拉深断裂点产生在凸模肩部转角附近,且始终承受两向不等拉伸,应变计算值与实际拉深测定值相符;切角板坯的拉深断裂点则转移至接近凹模口的侧壁处,且始终处于压剪组合变形状态,断裂时板厚应变相当小,认为倾向于剪切断裂。切角板坯断裂点的拉、压应力组合效应使该点板厚几乎不变,是提高拉深极限的重要因素之一。     

Modelling the kinetics of strain induced precipitation in Nb microalloyed steels

Strain induced precipitation is a key phenomenon that controls the microstructure evolution during the finish rolling stages of microalloyed steels. Extensive research has shown that the precipitation of Nb(CN) delays the onset of recrystallisation. This paper presents a model to describe the precipitation kinetics during isothermal holding following high temperature deformation in Nb-containing steels. The model is based on the assumption that heterogeneous nucleation of precipitates on dislocations and enhanced coarsening due to pipe diffusion are responsible behind the accelerated kinetics observed in strain induced precipitation. Results show a very good agreement between reported experimental observations and predictions of the present model for precipitate size and volume fraction evolution.