Ceramic-metal composites, or cermets, exhibit beneficial properties resulting in their use in many industrial applications. One challenge with cermets is mismatches in the coefficient of thermal expansion (CTE) values between the ceramic and metal phases that lead to residual stresses after processing, plasticity in the metal phase, internal stresses, and instability after thermal cycling. In order to make predictions of these properties to inform the design of cermets, we employ an incremental elasto-viscoplastic, self-consistent formulation to calculate the thermal, elastic, and plastic strains in two-phase polycrystalline cermet materials. This framework is extended to include temperature dependent properties, which are called implicitly within the temperature-dependent, incremental elasto-viscoplastic, self-consistent (TE-VPSC) model. Temperature-induced cooling and thermal cycling simulations are conducted using the TE-VPSC framework to study the residual stresses and plastic strains in the metal phases. Two materials are discussed in detail exhibiting stark differences based on the CTE between their ceramic and metal phases, WC/57-vol% Cu (exhibiting a pronounced CTE mismatch) and YO/27-vol% Nb (exhibiting a negligible CTE mismatch). The model demonstrates high residual stresses in the Cu phase during processing and reverse plasticity leading to recovery of plastic strain during thermal cycling of the WC/Cu cermet. Moreover, the model demonstrates relatively low residual stresses and plasticity in YO/Nb and a thermal stability point of 1251 °C, below which no plasticity develops in the cermet. We employ the TE-VPSC model as a design tool for cermets to systematically investigate the effects of process-induced microstructure variations (volume fraction, grain aspect ratio, and crystallographic texture are investigated) and compositional differences (19 compositions are explored) on the residual stress, degree of plasticity in the metal phase, and thermal stability point. The computational efficiency of the TE-VPSC framework makes it a desktop design tool that can be used to quantify the impact of changing composition, processing, and thermo-mechanical loading on the performance of the cermet, which can help reduce the number of time intensive and costly high temperature experiments.

中文翻译：

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通过弹粘塑性晶体塑性建模综合分析金属陶瓷设计和热循环稳定性


陶瓷金属复合材料或金属陶瓷表现出有益的特性，使其在许多工业应用中得到使用。金属陶瓷面临的一项挑战是陶瓷相和金属相之间的热膨胀系数 (CTE) 值不匹配，这会导致加工后产生残余应力、金属相的塑性、内应力以及热循环后的不稳定。为了预测这些特性，为金属陶瓷的设计提供信息，我们采用增量弹粘塑性自洽公式来计算两相多晶金属陶瓷材料中的热应变、弹性应变和塑性应变。该框架扩展到包括温度相关属性，这些属性在温度相关增量弹粘塑性自洽 (TE-VPSC) 模型中隐式调用。使用 TE-VPSC 框架进行温度诱导冷却和热循环模拟，以研究金属相中的残余应力和塑性应变。详细讨论了两种材料，它们的陶瓷相和金属相之间的 CTE 存在明显差异：WC/57-vol% Cu（表现出明显的 CTE 失配）和 YO/27-vol% Nb（表现出可忽略不计的 CTE 失配）。该模型展示了加工过程中铜相中的高残余应力和逆塑性，导致 WC/Cu 金属陶瓷热循环过程中塑性应变的恢复。此外，该模型显示 YO/Nb 具有相对较低的残余应力和塑性，热稳定点为 1251 °C，低于该温度，金属陶瓷不会产生塑性。 我们采用 TE-VPSC 模型作为金属陶瓷的设计工具，系统地研究工艺引起的微观结构变化（研究了体积分数、晶粒长宽比和晶体织构）和成分差异（探索了 19 种成分）对残余物的影响。应力、金属相的塑性程度和热稳定点。 TE-VPSC框架的计算效率使其成为桌面设计工具，可用于量化成分、加工和热机械载荷变化对金属陶瓷性能的影响，这有助于减少时间密集型的设计以及昂贵的高温实验。