Study on microstructure evolution and deformation behavior of Mg– Zn base alloy pipes during hot bending

Abstract

The strong basal fiber texture of magnesium (Mg) alloy pipes usually leads to poor secondary forming performance. In this study, Mg–2Zn-0.4Ce-0.4Mn (ZME) and Mg–2Zn-0.4Ce-0.4Mn-0.2Ca (ZMEX) pipes were prepared. Compared with the ZME pipe, the ZMEX pipe with a weaker initial texture exhibits excellent bending performance, with a peak load displacement (PLD) of 14.5 ± 0.5 mm and a total energy absorption (TEA) of 142.9 ± 1.7 J. The difference in bending performance between the two pipes is related to the deformation mechanism during hot bending. In the hardening stage, the deformation of the compression zone (CZ) of the two pipes is mainly ETW nucleation, and the overall proportion of twin grains is similar. However, in the tensile zone (TZ), the deformation of the ZME pipe is mainly prismatic slip, while the weak initial texture of the ZMEX pipe leads to the deformation dominated by both prismatic and multiple pyramidal slips, resulting in a higher hardening rate. In the softening stage, the deformation behavior in the CZ and TZ of both pipes tends to be similar. In addition, it is revealed that the softening phenomenon of both pipes after the bending displacement reaches PLD is caused by discontinuous dynamic recrystallization (DDRX) driven by high-density dislocations accumulated in the later CZ and TZ. The research on the microstructure evolution and deformation mechanism of Mg alloy pipe during bending deformation carried out in this study is of great significance for optimizing its secondary forming controllability and further expanding its application.

Keywords

• Mg alloy pipe
• Microstructure evolution
• Deformation mechanism
• Bendability