Constitutive behavior of a SIMA processed magnesium alloy by employing repetitive upsetting-extrusion (RUE)

• Published in: Journal of alloys and compounds 2018-06, Vol.748, p.694-705
• Main Authors: Xu, Yan, Chen, Chen, Jia, Jianbo, Zhang, Xuxing, Dai, Haohao, Yang, Yue
• Format: Article
• Language: English
• Subjects: Alloys; AZ91D magnesium alloy; Compacting; Compression tests; Computer simulation; Constitutive modeling; Constitutive models; Deformation; Deformation mechanisms; Elastic deformation; Extrusion; Magnesium; Magnesium base alloys; Plastic deformation; Repetitive upsetting-extrusion; Rheological properties; Semi-solid; Semisolids; Strain hardening; Strain rate; Thermal simulation; Thermal simulators; Thixoforming; Thixotropic compression; Upsetting
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.03.205

Thixotropic compression tests were carried out on a repetitive upsetting-extrusion (RUE) processed AZ91D magnesium alloy at temperatures ranging from 500 °C to 550 °C by using a Gleeble-1500 thermal-mechanical simulator. Semi-solid stress-strain data were obtained. A modified constitutive model was established to describe the thixotropic behavior of the RUE strained alloys. The results revealed that three stages of elastic-like deformation, strain hardening deformation and rheological viscoplastic deformation were involved in the thixoforming process. Furthermore, the compressed microstructures in semi-solid state were investigated with referring to microstructure observation. Dominant deformation mechanisms during the thixotropic compression were considered as the slipping or rotating mechanism of the solid particles along the liquid films, the slipping mechanism between the solid particles, the plastic deformation mechanism of the solid particles and the DRX behavior of the solid particles, whose function varied with the change of temperature and strain rate. [Display omitted] •Thixotropic behavior was clarified for the RUE-based SIMA treated AZ91D alloy.•Improved constitutive relationships relate to thixotropic factors were proposed.•An adjusting factor which denotes the effect of liquid was proposed.•Semi-solid microstructures after thixotropic compressions were clarified.•Deformation mechanisms during the thixotropic compression were discussed.