Shchyglo Oleg, Hammerschmidt Thomas, Čak Miroslav, Drautz Ralf, Steinbach Ingo
Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum, Universitätsstr. 150, Bochum 44801, Germany.
Materials (Basel). 2016 Aug 9;9(8):669. doi: 10.3390/ma9080669.
In this study we propose a unified multi-scale chemo-mechanical description of the BCT (Body-Centered Tetragonal) to BCC (Body-Centered Cubic) order-disorder transition in martensitic steel by adding the mechanical degrees of freedom to the standard CALPHAD (CALculation of PHAse Diagrams) type Gibbs energy description. The model takes into account external strain, the effect of carbon composition on the lattice parameter and elastic moduli. The carbon composition effect on the lattice parameters and elastic constants is described by a sublattice model with properties obtained from DFT (Density Functional Theory) calculations; the temperature dependence of the elasticity parameters is estimated from available experimental data. This formalism is crucial for studying the kinetics of martensite tempering in realistic microstructures. The obtained extended Gibbs energy description opens the way to phase-field simulations of tempering of martensitic steel comprising microstructure evolution, carbon diffusion and lattice symmetry change due to the ordering/disordering of carbon atoms under multiaxial load.
在本研究中，我们通过在标准的相图计算（CALPHAD）类型的吉布斯自由能描述中加入机械自由度，提出了一种统一的多尺度化学 - 力学描述，用于马氏体钢中体心四方（BCT）到体心立方（BCC）有序 - 无序转变。该模型考虑了外部应变、碳成分对晶格参数和弹性模量的影响。碳成分对晶格参数和弹性常数的影响通过一个亚晶格模型来描述，该模型的性质由密度泛函理论（DFT）计算得到；弹性参数的温度依赖性则根据现有的实验数据进行估算。这种形式体系对于研究实际微观结构中马氏体回火动力学至关重要。所得到的扩展吉布斯自由能描述为马氏体钢回火的相场模拟开辟了道路，该模拟包括微观结构演变、碳扩散以及在多轴载荷下由于碳原子的有序/无序导致的晶格对称性变化。
