Effect of aging time on discontinuous precipitates, continuous precipitates and mechanical properties of AZ80A magnesium alloy

Dependence of Tensile Properties and Fracture Behaviors on the Fractions of Continuous and Discontinuous Precipitates in Peak-Aged AZ80A Magnesium Alloy

“…This is because when a micro-crack in the CP region grows into the boundary of the DP region, it alters its growth direction to avoid the DP region. This phenomenon is consistent with our previous argument that the precipitation-strengthening effect in DP regions is much stronger than in CP regions [ 28 , 31 ]. As a result, the fracture length in the CP region is much longer than that in the DP region, despite the fraction of CP and DP regions being almost equal.…”

“…It would accelerate the CP reaction in the following aging process because the CP reaction is controlled by volume diffusion, and a higher vacancy concentration increases the diffusion coefficient [ 24 ]. According to the DP reaction mechanism [ 23 , 28 ], the DP reaction only stops when the Al atoms are exhausted by the CP reaction or when the CP precipitates grow large enough to impede the movement of the DP reaction front. Therefore, when the solution temperature increases, the CP reaction is accelerated, and the DP reaction is terminated earlier, leading to a smaller final fraction of DP regions.…”

“…Researchers control the ratio of CP- and DP-region fractions using many methods, including adjusting the aging temperature and time [ 24 , 28 ], grain refinement [ 29 ], micro alloying [ 22 , 30 ], and pre-twinning deformation [ 31 ]. However, other factors affecting the mechanical properties are also induced, such as the sizes and distribution of the precipitates, grain size, new strengthening phases, and twinning.…”

Grain-Scale In-Situ Study of Discontinuous Precipitation in Mg-Al

“…One limitation of in-situ TEM studies is the restriction to very small volumes of material; usually only one DP region in one grain is observed in any experiment. Attempts have also been made to perform "quasi-insitu" analysis of DP growth in the scanning electron microscope (SEM) [15] in the Mg-Al system, in which the same region is tracked, but heating takes place outside the microscope. This method allows for the evolution of DP in one region to be followed, but the sampling frequency is very low.…”