Simple: GBS displacement = 0.22 × strain × grain size (0.22 is a well-defined physical parameter, explained below).
Scope: Covers 39 materials with distinct crystal structures and alloy compositions, grain sizes nm - mm, strains 0.1%-161%
The mechanical behavior of polycrystalline metals and alloys is significantly influenced by grain boundary sliding (GBS), a key mechanism of plastic deformation. GBS plays a crucial role in determining properties like creep, superplasticity, strength, and ductility, all of which are essential for high-performance alloys used in various industries.
Challenges
While the concept of GBS originated in 1913, key challenges remain after over 100 years of research. These include the lack of a unified approach for characterizing GBS and a clear understanding of how factors like stress, temperature, and substructure influence it.
Materials
Table 1. Summary of experimental data
where μgbs is GBS displacement, dg is grain size, and ε is strain. hs=0.22 is a coefficient related to the strain enhancement factor and grain geometry.
GBS Analytical Models
In the analytical model of GBS, variables such as stress, temperature, strain, grain size, stress exponent, creep rate, and subgrain size are comprehensively considered. By constructing seven combinations of variables and combining the Soft Constrained Bayesian Regularization Neural Network (SCBRNN) with statistical analysis methods, the model parameters are determined.
Findings
This study compiled a comprehensive grain boundary sliding (GBS) dataset encompassing a wide range of materials (Fe, ferritic steels, austenitic steels, Al, Mg, Cu, Zn, and their respective alloys), grain sizes (0.066-3250 μm), strain levels (0.1-161%), and deformation modes (creep, tensile, and superplasticity).
A unified method for GBS was proposed, converting all measurements to GBS displacement along the stress axis, enabling effective integration and comparison of experimental data from various sources.
The influence of different variables, alloy compositions, and mechanical behaviors on GBS was analyzed. Strain and grain size were revealed as the primary factors influencing GBS, and a simple GBS basic model was established: GBS displacement = 0.22 × strain × grain size (where 0.22 is a coefficient related to the strain enhancement factor and grain geometry).
This model can effectively predict GBS and has been successfully applied to predict the nucleation and growth of creep cavities.
Fig. 2. GBS displacement predicted by the GBS basic model for all materials under different conditions (left), and the corresponding regression plot of predicted values against experimental data (right).
This study provides data and theoretical support for grain boundary sliding (GBS). The study helps to a better understanding of material deformation behavior. It can serve as a reference for the evaluation of GBS and mechanical properties.
Future Research
Nanoscale GBS: Nanoscale data is limited in this study. Future work could systematically investigate GBS at the nanoscale and validate the applicability of the model.
Different conditions: The model covers creep, superplasticity, and tensile deformation. Future research could explore GBS under compression, irradiation, etc., to expand the applicability of the model.
