Jiaxin Zhao

Bio: Jiaxin Zhao is an academic researcher from Henan University of Science and Technology. The author has contributed to research in topics: Deformation (engineering) & Dynamic recrystallization. The author has an hindex of 1, co-authored 2 publications receiving 2 citations.

Dynamic precipitation and recrystallization mechanism during hot compression of Mg-Gd-Y-Zr alloy

Abstract: Hot compression tests of Mg-Gd-Y-Zr alloy at different deformation temperatures and strains were carried out with Gleeble-1500 simulator at strain rate of 0.002 s−1. The microstructure evolution of 400 °C/0.002 s−1 sample under different strain was analyzed emphatically by transmission electron microscopy and electron backscatter diffraction technology. Dynamic precipitation characteristics and nucleation-expansion mechanism of dynamic recrystallization (DRX) were discussed in detail. The results indicated that the dynamic precipitation takes place prior to DRX, and the morphology, size and distribution of precipitates change with increasing strain. At the later stage of deformation, the large-size hard phase β-Mg5(Gd,Y) can induce the particle-stimulated nucleation (PSN) mechanism under large strain and act as an effective nucleation site for DRX. In addition, we constructed a schematic diagram of the DRX nucleation-expansion mechanism of Mg-Gd-Y-Zr alloy under high temperature deformation. The first layer of DRX grains is formed by discontinuous dynamic recrystallization (DDRX) mechanism characterized by grain boundary bulge out, and the precipitates distributed at the original grain boundary promote DDRX nucleation; The expansion of necklace structure depends on continuous dynamic recrystallization (CDRX) mechanism; Subgrain division can further refine DRX grains.

Deformation behavior characterized by reticular shear bands and long chain twins in Mg-Gd-Nd(-Zn)-Zr alloys

Abstract: We analyzed the deformation behavior of Mg-Gd-Nd(-Zn)-Zr alloys under high temperature uniaxial compression, and reported two special nucleation mechanisms of dynamic recrystallization (DRX): Nucleation and expansion of DRX based on reticular shear bands (Shear band dynamic recrystallization, SBDRX) and long chain twins (Twin dynamic recrystallization, TDRX). The reticular shear bands in Mg-Gd-Nd-Zr alloy are mainly caused by the crossing of strain gradients from different directions, which is related to the high activity of pyramidal slip at high temperature. The addition of Zn makes the DRX mechanism mutate, and TDRX is dominant in Mg-Gd-Nd-Zn-Zr alloy. The nucleation of a large number of {10–12} twins is abnormal, which may be related to the decrease of I 2 stacking fault energy caused by Gd/Nd–Zn compound addition. Based on the mechanical properties and microstructure, it can be concluded that the addition of Zn can promote the DRX, reduce the deformation resistance and improve the workability.

Deformation behavior characterized by reticular shear bands and long chain twins in Mg-Gd-Nd(-Zn)-Zr alloys

Abstract: We analyzed the deformation behavior of Mg-Gd-Nd(-Zn)-Zr alloys under high temperature uniaxial compression, and reported two special nucleation mechanisms of dynamic recrystallization (DRX): Nucleation and expansion of DRX based on reticular shear bands (Shear band dynamic recrystallization, SBDRX) and long chain twins (Twin dynamic recrystallization, TDRX). The reticular shear bands in Mg-Gd-Nd-Zr alloy are mainly caused by the crossing of strain gradients from different directions, which is related to the high activity of pyramidal slip at high temperature. The addition of Zn makes the DRX mechanism mutate, and TDRX is dominant in Mg-Gd-Nd-Zn-Zr alloy. The nucleation of a large number of {10–12} twins is abnormal, which may be related to the decrease of I 2 stacking fault energy caused by Gd/Nd–Zn compound addition. Based on the mechanical properties and microstructure, it can be concluded that the addition of Zn can promote the DRX, reduce the deformation resistance and improve the workability.