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用晶体热粘塑性模型研究了镍基合金中γ与γ′相的非弹性行为,进行了在晶体塑性理论基础上考虑镍基高温合金中的随机分布相结构对其蠕变与损伤过程的数值模拟.模拟假定合金中γ′相的尺寸及分布具有随机性,γ与γ′相在高温下的变形、损伤用温度相关的晶体粘塑性损伤本构关系进行计算,计算结果与周期体胞模型进行了比较.结果表明:γ′相随机分布模型能够反映镍基合金微观变形和应力分布不均匀、局部剪切变形和可能的破坏倾向;该模型的蠕变分析结果较周期体胞模型合理. 相似文献
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张诚江 《稀有金属材料与工程》2019,48(12):3930-3938
对3种不同取向的DD6镍基单晶高温合金进行了980℃下的蠕变试验,结果表明镍基单晶高温合金蠕变失效机理是材料内部微孔洞的萌生与微裂纹的扩展,其本质是由位错运动造成的。采用透射电镜(TEM)对蠕变初期[001]、[111]和[011]3种取向的单晶合金的位错形貌进行观测,发现其分别符合八面体滑移系开动、六面体滑移系开动与两滑移系同时开动的特征。针对上述微观现象,基于晶体塑性理论建立了考虑Orowan效应与位错阻碍效应的蠕变本构模型与蠕变损伤模型,并根据试验得到的蠕变曲线拟合了模型参数。该模型的有限元模拟结果与单晶材料的蠕变断口形貌相互印证,解释了单晶蠕变的各向异性的力学行为。 相似文献
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《金属学报》2015,(3)
基于晶体塑性理论,建立了滑移和孪生机制耦合的孪生诱导塑性(TWIP)钢单晶晶体塑性本构模型,通过引入孪晶体积分数及其饱和值,分别考虑了孪生对硬化及滑移的影响,对该本构模型进行数值实现.并通过ABAQUS/UMAT平台上的二次开发,将其应用于TWIP钢单晶典型取向单向加载条件下的力学行为模拟.分析了单晶不同取向下塑性变形的微观机理和滑移系、孪生系的启动状态及其对宏观塑性的影响,尤其是模拟得到黄Cu取向和S取向加载过程的应力突变,再现了Cu单晶实验中的应力陡降现象.结果表明,孪晶体积分数较小时,对应变硬化影响较小;随着孪晶体积分数的增加,对应变硬化的影响逐渐明显;当孪晶体积达到一定量时,孪晶体积达到饱和,孪生增量为0,晶体滑移转向,新的滑移系启动,应力突降. 相似文献
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为了研究晶体取向对镍基单晶高温合金纳米压痕行为的影响,采用带原子力显微镜的Berkovich压头对[001], [011]和[111]取向的镍基单晶高温合金开展了纳米压痕试验。试验结果显示晶体取向对压痕载荷-深度曲线、硬度和弹性模量有显著影响。晶体取向会影响γ^"强化相形状和体积分数,进而会影响其力学性能。采用晶体塑性理论对三种典型晶体取向下的纳米压痕响应和分解切应力分布开展有限元模拟,模拟结果与试验结果符合得较好。 相似文献
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双剪切试样在镍基单晶合金蠕变变形损伤和寿命研究中的应用 总被引:3,自引:0,他引:3
在对不同滑移系的双剪切试样进行蠕变实验的基础上,结合单向应力拉伸蠕变实验,并利用晶体滑各向异性蠕变损伤本构模型和有限元程序,对双剪切蠕变试样进行了研究。结果表明,对剪切试样受剪区域的应力状态基本为均匀分布且随蠕变时间变化很小,大部分受剪区域为单滑移系开动,提出的基于蠕变γ′相筏化规律的蠕变损伤本构模型,结合有限元(FEM)分析可以很好地描述双剪切试样的蠕变损伤规律,并可以和单向应力状态的实验结果联系起来,双剪切试样可以用来研究镍基单晶合金蠕变性能的晶体取向相关性,实验表明这种晶体取向相关性与开动滑移系类型及γ′相符代规律相关。 相似文献
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镍基单晶高温合金沉淀相尺度效应研究 总被引:1,自引:1,他引:0
对Ni_3Al(γ')沉淀相尺寸对镍基单晶高温合金拉伸性能的影响进行了研究。对镍基单晶高温合金而言,材料的屈服来源于位错以Orowan机制绕过沉淀相,而Orowan应力与沉淀相间距有关。根据这一机理,基于晶体塑性理论,引入一个本构方程以表征沉淀相尺寸对镍基单晶高温合金屈服强度的影响。采用该本构模型,分别计算了在[001]以及[111]2个取向下,含有尺寸为0.2~2.5μm沉淀相的镍基单晶高温合金屈服强度,并与试验结果进行了对比验证。结果表明,该模型可以准确表征镍基单晶高温合金沉淀相的尺度效应。 相似文献
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基于晶体塑性理论,考虑孪生软化效应建立了描述孪晶形核、增殖和长大的位错密度基晶体塑性有限元模型。应用该模型揭示了不同晶体取向Cu单晶拉伸变形过程中位错滑移、孪生激活及其交互作用下的宏观塑性行为演化规律,进一步分析了Cu多晶拉伸变形过程中晶粒间交互作用对孪生软化、应变硬化等宏观塑性行为的影响。结果表明:孪生具有明显的取向效应,在孪生主导塑性条件下,Cu单晶塑性变形过程中孪晶增殖导致应力-应变曲线存在明显的应力突降现象,其塑性变形分为滑移、孪生及位错与孪晶交互作用3个阶段;此外,随着饱和孪晶体积分数增加,Cu单晶塑性变形过程中第3阶段的应变硬化率也随之提升。进一步模拟Cu多晶拉伸变形的塑性行为可知,在晶粒间交互作用下孪晶形核、增殖和长大过程中不会出现应力突降现象,与Cu单晶相比整个塑性变形过程具有更高的应变硬化率;Cu多晶塑性变形过程中位错密度在晶界处出现集中现象,孪晶也容易在晶界处形成。 相似文献
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M.Sakaguchi M.Okazaki 《金属学报(英文版)》2004,17(4):361-368
An analytical method to investigate the morphological evolution of the cellular microstructure is explored and proposed. The method is essentially based on the Eshelby‘s micromechanics theory, and it is extended so as to be applied for a material system containing inclusions with high volume fraction, by employing the average stress field approximation by Mori and Tanaka. The proposed method enables us to discuss a stable shape of precipitate in the material system, which must be influenced by many factors: e.g., volume fraction of precipitate; Young‘s modulus ratio and lattice misfit between matrix and precipitate; external stress field in multiaxial state; and heterogeneity of plastic strain between matrix and precipitate. A series of numerical calculations were summarized on stable shape maps. The application of the method to predict the γ‘ rafting in superaUoys during creep showed that the heterogeneity of plastic strain between matrix and precipitates may play a significant role in the shape stability of the precipitate. Furthermore, it was shown that the method was successfully applied to estimate the morphology of the cellular microstructure formed in CMSX-4 single crystal Ni-based superaUoy. 相似文献
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用固体与分子经验电子理论(EET)计算研究了微量元素Er,Zr添加到铝合金中产生的Al3Er和Al(ZrIxEr1-x)相的价电子结构,探讨了不同Zr含量对Al3(ZrxFr1-x)相各电子结构参数的影响.计算结果表明:随着Zr原子含量的增加,表征强度性能的最强键上的共价电子对数na和相结构形成因子S会减小,这说明合金... 相似文献
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对商业纯钛(CP-Ti)退火后冷轧9%变形的板材,利用电子背散射衍射(EBSD)和扫描电子显微镜(SEM)评估了晶粒中激活的滑移系统和孪生系统。同时,采用反应应力(RS)模型模拟了变形晶粒中滑移系统的激活以及晶粒之间的相互作用,该模型将晶粒塑性变形过程视为外加应力和统计变化的晶间反应应力共同作用的结果。结果表明,反应应力模型适用于评价多晶钛的变形行为。该模型预测了变形后的钛晶粒内发生的滑移,实验数据证实了该模型的正确性。变形晶粒中滑移和孪晶的分布不均匀,与晶粒应变分布不均匀相对应。这种不均匀的晶粒应变也可以由取向不同的相邻晶粒变形而产生。当一个晶粒的塑性变形与其相邻晶粒的塑性变形有显著差异时,就会触发附加的局部滑移,从而降低晶粒间的应变不协调。塑性应变在某些情况下是通过机械孪生来实现的,它与滑移协同以满足晶内和晶间的应变连续性。 相似文献
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A novel limiting strain energy strength theory 总被引:1,自引:0,他引:1
刘光连 《中国有色金属学会会刊》2009,19(6):1651-1662
With applied dislocation theory, the effects of shear and normal stresses on the slide and climb motions at the same section of a crystal were analyzed. And, based on the synergetic effect of both normal and shear strain specific energies, the concept of the total equivalent strain specific energy (TESSE) at an oblique section and a new strength theory named as limiting strain energy strength theory (LSEST) were proposed. As for isotropic materials, the plastic yielding or brittle fracture of under uniaxial stress state would occur when the maximum TESSE reached the strain specific energy, also the expressions on the equivalent stresses and a function of failure of the LSEST under different principal stress states were obtained. Relationship formulas among the tensile, compressive and shear yield strengths for plastic metals were derived. These theoretical predictions, according to the LSEST, were consistent very well with experiment results of tensile, compressive and torsion tests of three plastic metals and other experiment results from open literatures. This novel LSEST might also help for strength calculation of other materials. 相似文献
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Thermal stresses in metal matrix composites (MMC) can induce plastic deformation and damage accumulation in the region close to the reinforcements. In this connection, Al-4% Cu-based MMC reinforced with 10, 20 and 30% Al2O3 short fibres were characterized by internal friction (IF) measurements. As a function of the temperature, a maximum of damping has been observed in the composites at ca 150 K during cooling. This maximum is absent in the corresponding unreinforced AlCu alloy. The maximum is attributed to the generation and motion of dislocations produced by high thermal stresses at metal-fibre interfaces. The height of the maximum is found to be an index of the extent of relaxation of thermal stresses by the plastic deformation of the metal matrix. IF measurements have allowed us to identify whether plastic flow in the matrix or damage accumulation at matrix-fibre interfaces take place for different composites. 相似文献
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以γ’相强化的Co-Al-W高温合金(Co-9Al-xW,x=8、9、10,原子分数,%)为研究对象,耦合CALPHAD和晶体塑性本构关系,建立了高温加载时微观组织演化的三元弹塑性相场模型,考察了W含量对蠕变过程中γ’相演化行为和蠕变性能的影响。结果表明,随W含量增加,γ’相体积分数增加,γ基体塑性变形降低,筏化形成并提前,导致蠕变性能提高。不变矩分析表明,9W和10W合金中筏组织形成是出现稳态蠕变阶段的主要原因。应力/应变分析表明,高W合金γ基体中较大的错配应力减小了塑性变形。 相似文献
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A finite element analysis was carried out on the development of residual stresses during the cooling process from the fabrication temperature in the SiCp reinforced AI matrix composites. In the simulation, the two-dimensional and random distribution multi-particle unit cell model and plane strain conditions were used. By incorporating the Taylor-based nonlocal plasticity theory, the effect of particle size on the nature, magnitude and distribution of residual stresses of the composites was studied. The magnitude thermal-stress-induced plastic deformation during cooling was also calculated. The results show similarities in the patterns of thermal residual stress and strain distributions for all ranges of particle size. However, they show differences in magnitude of thermal residual stress as a result of strain gradient effect. The average thermal residual stress increases with decreasing particle size, and the residual plastic strain decreases with decreasing particle size. 相似文献
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利用Instron 电子拉伸机和分离式霍普金生压杠(SHPB)实验装置, 研究了准静态和动态压缩条件下热轧TB2钛合金织构多晶板的力学性能。对TB2钛合金板材的轧向、横向以及轧制平面内与轧向成45°等3个方向进行了压缩实验, 得到了不同应变速率下的应力-应变曲线。结果表明:热轧TB2钛合金板材不同方向上的流变应力均随应变速率的增加而增加, 表现出明显的应变速率强化效应。准静态和动态力学性能均表现出各向异性, 且准静态和动态压缩行为规律不一致。考虑准静态和动态变形时可能的塑性变形机制, 基于微观晶体塑性变形理论, 定性讨论了热轧织构多晶TB2钛合金板屈服强度的各向异性 相似文献
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ELECTRONDIFFRACTIONPATTERNSANALYSISOFPRECIPITATESINLD_(10)ALLOY¥Jin,Tounan;Yin,Zhimin(DepartmentofMaterialsScienceandEngineer?.. 相似文献