Structure Refinement and Fragmentation of Precipitates under Severe Plastic Deformation: A Review

Abstract

During severe plastic deformation (SPD), the processes of lattice defect formation as well as their relaxation (annihilation) compete with each other. As a result, a dynamic equilibrium is established, and a steady state is reached after a certain strain value. Simultaneously, other kinetic processes act in opposite directions and also compete with each other during SPD, such as grain refinement/growth, mechanical strengthening/softening, formation/decomposition of solid solution, etc. These competing processes also lead to dynamic equilibrium and result in a steady state (saturation), albeit after different strains. Among these steady-state phenomena, particle fragmentation during the second phase of SPD has received little attention. Available data indicate that precipitate fragmentation slows down with increasing strain, though saturation is achieved at higher strains than in the case of hardness or grain size. Moreover, one can consider the SPD-driven nanocrystallization in the amorphous phase as a process that is opposite to the fragmentation of precipitates. The size of these crystalline nanoprecipitates also saturates after a certain strain. The fragmentation of precipitates during SPD is the topic of this review.

Microstructure and Mechanical Properties of the Joints from Coarse- and Ultrafine-Grained Al-Mg-Si Alloy Obtained via Friction Stir Welding

“…The first one was that, for the UFG BM, β″ precipitates were also observed; however, their size was reduced ( Figure 6 a) compared to the CG BM ( Figure 5 a). SPD processing may result in various phenomena that occur with second-phase precipitates, such as acceleration of precipitation [ 36 ], fragmentation due to severe shear forces [ 37 ], or dissolution [ 38 ]. Based on a comparison between Figure 5 a and Figure 6 a, two final processes could have taken place in the case of the I-ECAP process on the Al-Mg-Si alloy.…”

The Cold Angular Rolling Process of Copper Sheets: Unraveling Plastic Deformation Behavior and Unveiling Microstructural Transformations

“…This trend is also reported in a comparison of grain sizes of Cu after various SPD techniques as well as ball milling. [ 125 ]…”

“…This trend is also reported in a comparison of grain sizes of Cu after various SPD techniques as well as ball milling. [125] The mechanical properties taken from different references are often not directly comparable to each other due to their strainrate and sample-size dependency. Thus, the summarized data of yield strength and ductility in Table 4 are only for general comparison.…”

The Effect of Rotary-Die Equal-Channel Angular Pressing Process on the Microstructure, the Mechanical and Friction Properties of GW103 Alloy

“…The above problems were solved by the development of the severe plastic deformation (SPD) technique, which is considered an effective method to simultaneously improve the strength and ductility. The grain refinement process for bulk materials or powder consolidation was induced by applying the accumulated high shear strain in the SPD process [13][14][15]. Equal channel angular pressing (ECAP) and high-pressure torsion (HPT) are two typical methods that have been widely used in the research on bulk Mg alloys due to their excellent refining ability in both grains and precipitates [16][17][18][19][20].…”