In-situ tensile characterization of micropore evolution in Al–Si alloys using a novel tracking algorithm

The influence of micropore characteristics on stress-limited crack propagations during tensile tests of Al-Si alloys is still qualitative rather than quantitative. In this study, in-situ X-ray computed tomography (XCT) has been employed to obtain the micropore damage evolution quantitatively in different regions of the uniaxial tension samples. By developing a novel micropore-tracking algorithm (MPTA), the characteristics of individual micropores can be quantified in nucleation, growth, and coalescence stages. The results reveal pronounced heterogeneity in micropore evolution. Prior to fracture, the ratio of maximum to minimum micropore growth rates in the spoke region is 15, while the average growth rate in the rim region (44.91) is substantially higher than that in the spoke region (13.01). Compared to classical micropore growth models, the Huang model shows better agreement with experimental observations (MRE = 0.83%, MaxRE = 3.74%) than the R-T model (MRE = 1.11%, MaxRE = 4.32%). The integration of digital volume correlation (DVC), three-dimensional fracture surface and SEM fractography further reveals region-dependent fracture mechanisms. In the spoke region, cracks initiate from edge micropores and propagate along micropore aggregation zones, accelerating fracture, whereas in the rim region, local strain induces oriented micropore coalescence bands that trigger fracture. Therefore, the findings highlight the influence of individual micropore heterogeneity and regional differences on fracture behavior, providing critical experimental evidence and guidance for improving micropore models and enhancing fracture prediction accuracy.