2020 journal article

Twinning behaviors and grain refinement mechanisms during friction stir processing of Zr alloy

MATERIALS CHARACTERIZATION, 163.

By: S. Li*, B. Luan*, L. Chu, X. Zhang*, G. Yuan, R. Liu*, K. Murty n, Q. Liu*

co-author countries: China 🇨🇳 United States of America 🇺🇸
Source: Web Of Science
Added: August 10, 2020

The twinning behaviors and grain refinement mechanisms during friction stir processing (FSP) of Zircaloy-4 were studied. The main deformation mode changed due to temperature and strain gradient existed in different regions of FSP sample. The 101¯2 and 101¯1 twins were activated successively in thermo-mechanically affected zone (TMAZ) but reduced rapidly and replaced by dislocations slip in stir zone (SZ) because of the elevated temperature and decreased grain size. Accordingly, the grain refinement mechanisms also varied with the deformation modes. A new recrystallization mechanism, twinning induced dynamic recrystallization (TDRX) was proposed for the first time in FSPed Zr alloy, which resulted in grain refinement in TMAZ. The occurrence of TDRX included the formation of slipped 101¯2 twin boundaries and the transformation of 101¯1 twins into high angle grain boundaries (HAGBs); these were attributed to the interaction between twins and dislocations. In contrast, continuous dynamic recrystallization (CDRX) related to dislocations slip at higher temperatures dominated the process of grain refinement in SZ, and finally the ultrafine grains with average size of ~1 μm were obtained.