IN718单晶微柱体锯齿状变形的晶体塑性分析

Crystal plasticity model for the serrated behavior of single-crystal IN718 micropillars

摘要:

为较为准确可靠地预测IN718合金服役于各种复杂工况下的力学响应,开展了位移控制条件下微米尺寸IN718合金单晶锯齿状变形行为的理论建模研究工作.首先,基于微压缩测试的实验观察,建立了能够较为真实反映位移控制下晶体材料变形的“变形块-弹簧”力学分析模型.进而,通过分析晶体材料锯齿状变形行为中的应变强化、流动法则、加卸载准则以及应变突变判据等建模要素,构建了描述该行为的连续化晶体塑性本构理论模型之后,应用该模型分别研究了单滑移与双滑移取向的IN718合金单晶微柱体的轴向压缩响应,并与对应微压缩实验结果进行了比较.研究结果表明,基于上述理论模型预测的IN718单晶柱体轴向力学响应出现了加载、卸载以及应变突变3种变形方式,呈现出明显的锯齿状变形行为,与对应实验测试结果具有很好的吻合性.基于连续介质框架构建的微尺度锯齿状塑性本构模型,可为经典的连续化晶体塑性理论在亚微米尺度领域的发展提供有力理论支撑.

Abstract:

To predict the mechanical response of IN718 alloy under various complex conditions accurately and reliably, the theoretical modeling of serrated plasticity of microsized single-crystal IN718 alloy under displacement control was carried out. Starting from the micro-compression test, a simple deformable body-spring model was proposed to further elucidate the serrated plasticity under the displacement control. Subsequently, the independent modeling elements such as strain hardening, flow rule, loading-unloading criterion, and strain burst criterion were taken into consideration. Then, a continuum constitutive model for the serrated plasticity was established. This model was used to study the compression response of IN718 micropillars with single slip and double slip orientation, respectively. The simulations produced clearly a series of visible strain bursts, loading and unloading process in micropillar plasticity, and the exhibited serrated flows are comparable with the corresponding experimental observations. The proposed continuum model for the serrated plasticity can provide a strong theoretical support for the development of the classical crystal plasticity theory in the sub-micron scale.