目的 研究一种铸态Ni-Cr-Co基高温合金的宽温度和应变速率范围条件下的热变形行为,分析变形温度和应变速率对流变应力的影响规律和特征,利用元胞自动机（CA）方法建立合金热变形微观组织演化预测模型,为预测并控制高温合金热变形组织演化和优化热加工工艺提供理论依据。方法 在温度1 020~ 1 140 ℃、应变速率0.01~10 s-1及应变0.16~0.92条件下,在热模拟试验机上对均匀化热处理后的试样进行等温热压缩试验,利用光学显微镜（OM）、电子背散射衍射（EBSD）等表征手段观察不同变形参数下压缩试样的显微组织,分析动态再结晶（DRX）行为。基于流变应力数据和位错密度理论,利用Matlab构建合金热压缩微观组织CA预测模型,并通过实验结果进行对比验证。结果 铸态Ni-Cr-Co基高温合金流变应力随变形温度的升高或应变速率的降低而下降,流变应力变化呈现动态再结晶典型特征,在低温（1 020~ 1 050 ℃）大应变下,晶界开裂导致流变应力持续下降。合金热变形温度敏感性指数θ绝对值随应变速率的增加而增大,高应变速率下绝热升温效应加剧动态软化作用,应变速率敏感性指数m与温度呈正相关关系,在1 080 ℃以上m值显著增加。所建CA模型在1 020 ℃和1 140 ℃条件下对DRX体积分数和晶粒尺寸的预测值与实验结果的平均相对误差均在10%以内,可实现对合金变形后微观组织的模拟预测。结论 铸态Ni-Cr-Co基高温合金热变形过程中变形温度和应变速率对流变行为影响显著,低温变形时,晶界开裂是导致流变应力下降的主要原因,温度和应变速率敏感性指数与动态软化过程密切相关。所建立的CA模型能有效模拟合金热变形中的微观组织演化,为优化热加工工艺参数提供了可靠的理论支撑。
Abstract
The work aims to investigate the hot deformation behavior of an as-cast Ni-Cr-Co-based superalloy under a wide temperature and strain rate range, analyze the influence and characteristics of deformation temperature and strain rate on flow stress, and establish a prediction model for the microstructure evolution of the alloy using the cellular automata (CA) method, so as to provide a theoretical basis for microstructure prediction and control of the superalloy and optimizing the hot working process. After homogenization heat treatment, isothermal hot compression tests were carried out on the thermomechanical simulator at deformation temperature of 1 020-1 140 ℃, strain rate of 0.01-10 s-1 and strain of 0.16-0.92. The microstructure of the compressed samples under different deformation parameters was observed by optical microscope (OM) and electron backscatter diffraction (EBSD) to analyze the dynamic recrystallization (DRX) behavior. Based on the rheological stress data and dislocation density theory, a CA prediction model for microstructure evolution of the alloy during hot compression was constructed using Matlab, and the experimental results were compared and verified. The results showed that the flow stress of the as-cast Ni-Cr-Co-based superalloy decreased with the increase of deformation temperature or the decrease of strain rate. The change of flow stress presented typical characteristics of DRX. At low temperature (1 020-1 050 ℃), grain boundary cracking led to continuous decrease of flow stress at large strains. The absolute value of temperature sensitivity exponent θ increased with the increase of strain rate. The adiabatic heating effect at high strain rate intensified the dynamic softening effect. The strain rate sensitivity exponent m was positively correlated with temperature, and the value of m increased significantly above 1 080 ℃. The average relative errors of DRX volume fraction and grain size predicted by the CA model at 1 020 and 1 140 ℃ were within 10% compared with the experimental results, which could realize the simulation and prediction of the microstructure evolution after hot deformation. The deformation temperature and strain rate have a significant effect on the flow behavior of the as-cast Ni-Cr-Co based superalloy during hot deformation. At low deformation temperature, grain boundary cracking is the main reason for the decrease of flow stress. The temperature and strain rate sensitivity exponents are closely related to the dynamic softening process. The established CA model can effectively simulate the microstructure evolution of the alloy during hot deformation, providing reliable theoretical support for optimizing hot working process parameters.
关键词
铸态Ni-Cr-Co基高温合金 /
热变形 /
微观组织演化 /
CA模型
Key words
as-cast Ni-Cr-Co-based superalloy /
hot deformation /
microstructure evolution /
CA model
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基金
新疆维吾尔自治区自然科学基金青年科学基金项目（2025D01C342,2024D01C210); 天山英才-青年拔尖人才（2024TSYCJC0003）; 新疆高校基本科研业务费项目（XJEDU2025P102）; 庭州青年计划（2023QN08）
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