Real time investigation of the grain refinement dynamics in zinc alloy by synchrotron microradiography

Highlights: • Synchrotron radiation is a powerful tool to investigate grain refinement kinetics. • The grain size of ZA27 reduced from 205.4 to 65.8 μm after adding 1.1% TiB₂. • TiB₂ particles facilitate heterogeneous nucleation. • TiB₂ particles enhance dendrite fragmentation of primary α-Al. • TiB₂ particles constrain the dendrite growth. - Abstract: The grain refining performance of titanium diboride particles in zinc alloy was investigated by adding in situ formed Al–TiB₂ master alloy into ZA27 alloy. The results showed that TiB₂ particles could significantly refine the structure of ZA27. After adding 1.1% TiB₂, the average grain size decreased markedly from 205.4 μm to 65.8 μm. To characterize the mechanism by which TiB₂ refines the grain size, synchrotron microradiography technique was used for the first time to investigate the effect of TiB₂ on the grain nucleation and growth kinetics. Real-time observations revealed that TiB₂ particles refine ZA27 by facilitating heterogeneous nucleation, enhancing dendrite fragmentation and constraining the dendrite growth