Evolution of microstructure and mechanical properties in large-scaled complex titanium alloy castings during service based on quantitative abnormal microstructure analysis

Abstract

This investigation delves into the microstructural heterogeneities of large-scale complex titanium alloy castings (LCTACs), with a specific focus on the emergence of abnormal coarse grains (ACGs), which pose a potential threat to the casting's operational longevity. This comprehensive analysis meticulously maps the spatial distribution of ACGs within the LCTAC, employing statistical methodologies to examine these grains across different zones subjected to varying service durations. The study reveals a nuanced correlation between wall thickness and the tendency for microstructural coarsening during operational life, concurrently tracing the evolution of mechanical properties in typical zones. Results demonstrate a distinctive 'staircase-like' progression in grain size distribution, accentuated as wall thickness increases. Throughout the operational lifespan, microstructures in zones of differential wall thickness exhibit varied degrees of growth. Notably, zones with thicker walls display a more marked enlargement in microstructure. This phenomenon coincides with a substantial increase in the extent of ACGs, ultimately leading to a significant diminution in mechanical properties, evidenced by a reduction exceeding 15% in both tensile and yield strength.