Dynamic precipitation, microstructure and mechanical properties of Mg-5Zn-1Mn alloy sheets prepared by high strain-rate rolling

• Published in: Materials & design Vol. 100; pp. 58 - 66
• Main Authors: Chen, Chao, Chen, Jihua, Yan, Hongge, Su, Bin, Song, Min, Zhu, Suqin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-06-2016
• Subjects: Dynamic mechanical properties; Dynamic precipitation; Dynamic recrystallization; Dynamics; High strain rate rolling (HSRR); Magnesium base alloys; Mechanical properties; Mg-Zn-Mn alloys; Microstructure; Precipitates; Precipitation; Dynamic precipitation; Mg-Zn-Mn alloys; Dynamic recrystallization; High strain rate rolling (HSRR)
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2016.03.129

Mg-5Zn-1Mn (wt%) alloy sheets with good strength-ductility balance were successfully fabricated by high strain-rate rolling (HSRR) in a wide temperature range from 250°C to 400°C. The microstructural evolution, dynamic precipitation characteristics and mechanical properties of the as-rolled sheets were investigated. The results show that the dynamic precipitation plays a key role in the as-rolled microstructural evolution and the mechanical properties. The uniform and dispersive precipitates with high spatial distribution density mainly nucleated on the α-Mn particles and along the dislocations during the HSRR. A typical bimodal microstructure can be obtained even at the high rolling temperature (400°C) by the HSRR process due to the dynamic precipitates strongly pinning the boundaries of the dynamic recrystallization (DRX) grains or subgrains. The sheet fabricated by HSRR at 300°C exhibits high strength and excellent ductility, with the ultimate tensile strength (UTS), yield tensile strength (YS) and elongation (EL) to failure of 359MPa, 258MPa and 20.1%, respectively. The superior mechanical properties can be attributed to the ultrafine DRX grains featured with the bimodal microstructure and the precipitates with high density.
High density of nano-sized precipitates dynamically nucleated on the Mn particles and the high density of dislocations induced by the high strain rate rolling (HSRR). The precipitates can effectively suppress the growth of DRX grains by pinning the boundaries of the DRX grains or subgrains. The superior combination of strength and ductility for the sheet is contributed to the grain refinement and precipitation strengthening. [Display omitted]
•Mg-5Zn-1Mn alloy sheets with high strength and good ductility were fabricated by high strain-rate rolling.•The rolled sheets exhibit optimal mechanical properties with ultimate tensile strength of 359MPa and elongation of 20.1%.•The enhanced strength and ductility benefit from ultrafine XRD grains and high density of nano-precipitates.•The nano-sized Mg-Zn phases were dynamically precipitated by heterogeneous nucleation on dislocations and α-Mn particles.