TY - JOUR

T1 - Microstructure, texture evolution and tensile properties of extruded Mg-4.58Zn-2.6Gd-0.16Zr alloy

AU - Xiao, Lei

AU - Yang, Guangyu

AU - Chen, Jieming

AU - Luo, S.F.

AU - Li, Jiehua

AU - Jie, Wanqi

N1 - Publisher Copyright: © 2018 Elsevier B.V.

PY - 2019/1/28

Y1 - 2019/1/28

N2 - Microstructure, texture evolution and mechanical properties of extruded Mg-4.58Zn-2.6Gd-0.18Zr alloy were investigated at extrusion temperatures of 260 °C, 280 °C and 300 °C, extrusion ratios of 10, 15 and 30, and ram speeds of 3 mm s −1 and 6 mm s −1, respectively. The results indicated that the as-cast experimental alloy was composed of α-Mg matrix, coarse α-Mg + W(Mg 3Zn 3Gd 2) eutectic and icosahedral quasicrystalline I(Mg 3Zn 6Gd) phase. A small amount of undissolved W phases were detected after the homogenization treatment at 505 °C up to 16 h, while most I phase dissolved into the α-Mg matrix. The initial crystallites before extrusion were randomly oriented, and showed a typical random texture. After extrusions, all samples exhibited a bimodal microstructure consisting of fine Dynamic recrystallization (DRX) grains and coarse elongated un-DRX grains, and the formation of ultra-fine DRX grains only occurred in the sample with an extrusion ratio of 10 at 260 °C, 3 mm s −1, which was caused by the solute segregation in homogenized billets and non-uniformly distributed W phase during the extrusion process. A fiber texture with {0002} planes and <1̄21̄0> directions paralleled to the extrusion direction was observed to be dominant in all the extruded samples. Furthermore, the increase of extrusion ratio was found to be beneficial for the DRX process and refinement of grain size, and the maximum texture intensity was accordingly weakened, which resulted in a decrease of tensile yield strength but an increase of elongation. With increasing the extrusion temperature or ram speed, both the grain size and DRX fraction gradually increased. Consequently, the texture was randomized and the maximum texture intensity decreased, which led to a reduction of the elongation and tensile yield strength. The tensile failure behaviors under different extrusion conditions were found to be related with the contraction twin lamellas formed in the un-DRX grains and the string-like W phases.

AB - Microstructure, texture evolution and mechanical properties of extruded Mg-4.58Zn-2.6Gd-0.18Zr alloy were investigated at extrusion temperatures of 260 °C, 280 °C and 300 °C, extrusion ratios of 10, 15 and 30, and ram speeds of 3 mm s −1 and 6 mm s −1, respectively. The results indicated that the as-cast experimental alloy was composed of α-Mg matrix, coarse α-Mg + W(Mg 3Zn 3Gd 2) eutectic and icosahedral quasicrystalline I(Mg 3Zn 6Gd) phase. A small amount of undissolved W phases were detected after the homogenization treatment at 505 °C up to 16 h, while most I phase dissolved into the α-Mg matrix. The initial crystallites before extrusion were randomly oriented, and showed a typical random texture. After extrusions, all samples exhibited a bimodal microstructure consisting of fine Dynamic recrystallization (DRX) grains and coarse elongated un-DRX grains, and the formation of ultra-fine DRX grains only occurred in the sample with an extrusion ratio of 10 at 260 °C, 3 mm s −1, which was caused by the solute segregation in homogenized billets and non-uniformly distributed W phase during the extrusion process. A fiber texture with {0002} planes and <1̄21̄0> directions paralleled to the extrusion direction was observed to be dominant in all the extruded samples. Furthermore, the increase of extrusion ratio was found to be beneficial for the DRX process and refinement of grain size, and the maximum texture intensity was accordingly weakened, which resulted in a decrease of tensile yield strength but an increase of elongation. With increasing the extrusion temperature or ram speed, both the grain size and DRX fraction gradually increased. Consequently, the texture was randomized and the maximum texture intensity decreased, which led to a reduction of the elongation and tensile yield strength. The tensile failure behaviors under different extrusion conditions were found to be related with the contraction twin lamellas formed in the un-DRX grains and the string-like W phases.

UR - http://www.scopus.com/inward/record.url?scp=85058224977&partnerID=8YFLogxK

U2 - 10.1016/j.msea.2018.11.142

DO - 10.1016/j.msea.2018.11.142

M3 - Article

VL - 744.2019

SP - 277

EP - 289

JO - Materials science and engineering: A, Structural materials: properties, microstructure and processing

JF - Materials science and engineering: A, Structural materials: properties, microstructure and processing

SN - 0921-5093

IS - January

ER -