Microstructure and Mechanical Properties of Extruded Flame Retardant Mg-3Sm-1Gd-1Ca-0.5Zr Alloy

DONG Feihu; WANG Sheng; CHU Zhibing; CHENG Liren; CHE Chaojie; WANG Zi

doi:10.3969/j.issn.1674-6457.2025.11.017

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Journal of Netshape Forming Engineering ›› 2025, Vol. 17 ›› Issue (11) : 178-189. DOI: 10.3969/j.issn.1674-6457.2025.11.017

Light Alloy Forming

Microstructure and Mechanical Properties of Extruded Flame Retardant Mg-3Sm-1Gd-1Ca-0.5Zr Alloy

DONG Feihu^1,2, WANG Sheng^2,3, CHU Zhibing^1,*, CHENG Liren², CHE Chaojie^1,2, WANG Zi⁴

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Abstract

The work aims to develop the Mg-3Sm-1Gd-1Ca-0.5Zr (EVX311) alloy based on the traditional EV31 alloy, to study the microstructure, mechanical properties, and flame retardancy of the alloy in extruded state. Mg-3Sm-1Gd-1Ca-0.5Zr (EVX311) extruded plate was prepared by hot extrusion process with extrusion ratio of 20∶1, temperature of 350 ℃ and extrusion speed of 1 mm/min. The alloy contained Mg₂Ca, Mg₃RE, and Mg₅RE precipitation phases and the extruded alloy exhibited strong {0001} basal weave, and "bimodal structure" in the microscopic view. By transmission electron microscopy, the grain boundary bowing out due to the difference in dislocation density, high-density aggregation of dislocations within the grain, and dynamic recrystallization (PSN) phenomenon facilitated by a second phase with a micrometer scale were all observed. The yield strength of the extruded alloy reached 217.06 MPa, and a yield plateau occurred under the tensile action. Through the observation and analysis of the tensile fracture, it was concluded that the fracture mechanism was a mixed type of fracture and the ignition point of the extruded alloy reached 894 ℃. The EBSD of the extruded state alloy is characterized by a fine crystalline microstructure containing a large amount of dynamic recrystallization. The appearance of the yield plateau may be related to the cyclic interaction between the solute atoms Ca in the matrix and the pinning-depinning of the dislocations. The high ignition point of the alloy is closely related to the dense and highly oxidation-resistant film formed by Ca and rare earth elements, and the present alloy has the advantages of low elemental content and high ignition point as compared with the other flame-retardant alloys.

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Mg-3Sm-1Gd-1Ca-0.5Zr alloy / microstructure / mechanical properties / flame resistance / precipitation phase

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DONG Feihu, WANG Sheng, CHU Zhibing, CHENG Liren, CHE Chaojie, WANG Zi. Microstructure and Mechanical Properties of Extruded Flame Retardant Mg-3Sm-1Gd-1Ca-0.5Zr Alloy[J]. Journal of Netshape Forming Engineering. 2025, 17(11): 178-189 https://doi.org/10.3969/j.issn.1674-6457.2025.11.017

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Funding

National Natural Science Foundation of China (52175353); Shanxi Provincial Science and Technology Major Special Program, “Unveiling the List of Commanders” Project (202101110401009); Changchun Science and Technology Development Program (21GD03); Jilin Provincial Science and Technology Development Program (SK2202302038)