Non-targeted Microhardness Testing to Obtain Intrinsic Properties of Phases in Alloys

Microscale characterization of the mechanical properties of individual phases is critically important for understanding the macroscopic behavior of multiphase alloys. However, direct targeting of dispersed phases during microhardness testing is challenging due to indentation overlapping grain boundaries and is time-consuming. To resolve this problem, an alternative non-targeted microhardness (NTM) experimental/simulation testing strategy was developed for highly efficient automated microhardness equipment. A supplementary virtual NTM testing simulation program was developed and applied to two- and three-phase structures with different hardness values and phase dispersions. It was shown that the probability distribution function (PDF) obtained from an NTM test uniquely characterizes the intrinsic microhardness of individual phases for a specific multiphase structure and indentation load. This uniqueness allows inverse simulations to be applied to determine the intrinsic microhardness of individual phases in multiphase structures. Moreover, the proposed framework can be used to extract the intrinsic microhardness of dispersed phases when the indentation size is on the order of larger than the characteristic grain diameter. The proposed methodology improves phase-specific property characterization and supports the design of multiphase alloys. The NTM strategy has potential for the identification of solidification features, such as segregation, microporosity, and grain boundary imperfections. By establishing this baseline framework, future studies can compare virtual and experimental datasets obtained from the same structure to isolate and analyze these structural features.