In situ measurement of the orientation matrices for the austenite and martensite phases of the alloy Cu25Au30Zn45 across the interface was performed by synchrotron x-ray Laue microdiffraction at the ALS. Together with theoretical calculations, researchers verified directly and quantitatively the factors that contribute to the alloy’s elastically compatible interface, which ultimately leads to the ultralow fatigue property of phase transformation in martensitic materials. The approach can be generalized to characterize the evolution of microstructure when the transport properties are sensitive to the structural compatibility at the heterogenous phase boundaries. Article link.