Effect of Rare Earth Element Ce on the Bulk Texture and Mechanical Anisotropy of As-Extruded Mg-0.3Al- 0.2Ca-0.5Mn Alloy Sheets
ZHU Guijie1, WANG Siqing2, ZHA Min2, LI Meijuan1(), SUN Kai1(), CHEN Dongfeng1
1 Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413, China 2 Key Laboratory of Automobile Materials of Ministry of Education, School of Materials Science and Engineering, Jilin University, Changchun 130025, China
Cite this article:
ZHU Guijie, WANG Siqing, ZHA Min, LI Meijuan, SUN Kai, CHEN Dongfeng. Effect of Rare Earth Element Ce on the Bulk Texture and Mechanical Anisotropy of As-Extruded Mg-0.3Al- 0.2Ca-0.5Mn Alloy Sheets. Acta Metall Sin, 2024, 60(8): 1079-1090.
Because deformed magnesium alloys with low density and desirable mechanical properties can save energy and reduce emissions, they are in considerable demand in industrial applications. However, due to their hcp crystal structure, magnesium alloys have a limited number of slip systems that can be activated at room temperature. At present, many deformed magnesium alloys still face the problems of insufficient formability and poor mechanical anisotropy at room temperature, which limit the development of secondary forming processes. Meanwhile, many reports have proven that regulating the texture of deformed magnesium alloys is an effective strategy to improve their formability. Therefore, this study primarily employs the neutron diffraction technology, combined with microscopic characterization methods such as SEM and EBSD, to systematically study the effects of the minor rare earth element Ce on the microstructure, bulk texture, and mechanical anisotropy of extruded Mg-0.3Al-0.2Ca-0.5Mn magnesium alloy sheet. The results show that as the Ce content increases, second-phase particles in the extruded magnesium alloy sheet gradually transform from Al8Mn5 to Ce-containing Al8Mn4Ce and Al11Ce3 particles and the number density of second-phase particles increases remarkably. The addition of 0.05%Ce (mass fraction) did not considerably improve the basal texture of the sheet. However, after the addition of 0.5%Ce, fiber texture components distributed along the transverse direction (TD) are substantially reduced while the texture of (0002) pole figure of the alloy changed from a bimodal basal texture to a bimodal nonbasal texture along the extrusion direction (ED). This nonbasal texture formation is mainly caused by larger Ce-containing second-phase particles (> 1 μm) promoting the particle-stimulated nucleation effect and preferential growth of nonbasal-oriented recrystallized grains. Therefore, when 0.5%Ce is added, the basal texture of the alloy is remarkably optimized, so that the ratio of the tensile yield strength along TD to that along ED is close to 1, implying that the anisotropy of the extruded Mg-0.3Al-0.2Ca-0.5Mn alloy has been substantially reduced by the minor addition of Ce element.
Fund: National Key Research and Development Program of China(2023YFA1608801)
Corresponding Authors:
SUN Kai, professor, Tel: (010)69358821, E-mail: ksun@ciae.ac.cnLI Meijuan, professor, Tel: (010)69359040, E-mail: mjli@ciae.ac.cn
Table 1 Actual compositions of Mg alloys used in the present work
Fig.1 EBSD images (a, c, e) and grain size distributions (b, d, f) of the as-extruded AXM (a, b), AXM + 0.05Ce (c, d), and AXM + 0.5Ce (e, f) alloy sheets (dave—average grain size)
Fig.2 Low (a, c, e) and high (b, d, f) magnified SEM-backscattered electron (BSE) images of the as-extruded AXM (a, b), AXM + 0.05Ce (c, d), and AXM + 0.5Ce (e, f) alloy sheets (ND—normal direction, ED—extrusion direction)
Fig.3 XRD spectra of the as-extruded AXM, AXM + 0.05Ce, and AXM + 0.5Ce alloy sheets (a), and partially enlarged XRD spectra (b)
Fig.4 High magnification SEM-BSE images (a-c) and EDS analyses (d-f) of the as-extruded AXM (a, d), AXM + 0.05Ce (b, e), and AXM + 0.5Ce (c, f) alloy sheets, where Figs.4d-f are line-scan results of the typical second-phase particle at square regions A, B, and C in Figs.4a-c, respectively
Fig.5 (100) (a1-a3), (0002) (b1-b3), and (101) (c1-c3) pole figures (PFs) by neutron diffraction of the as-extruded AXM (a1-c1), AXM + 0.05Ce (a2-c2), and AXM + 0.5Ce (a3-c3) alloy sheets (TD—transverse direction)
Fig.6 Mechanical properties at room temperature of the as-extruded AXM (a), AXM + 0.05Ce (b), and AXM + 0.5Ce (c) alloy sheets along ED and TD; and tensile yield strength (TYS) ratio along ED and TD (d)
Sample
TYS / MPa
UTS / MPa
EL / %
ED
TD
ED
TD
ED
TD
AXM
171.6 ± 0.5
100.2 ± 1.8
226.8 ± 0.7
208.3 ± 1.0
19.1 ± 0.9
19.8 ± 0.6
AXM + 0.05Ce
174.3 ± 1.3
98.6 ± 2.4
233.1 ± 1.8
202.5 ± 4.1
13.7 ± 1.3
12.8 ± 2.4
AXM + 0.5Ce
140.7 ± 1.5
138.5 ± 2.6
218.0 ± 1.5
219.1 ± 2.1
13.1 ± 1.1
11.3 ± 0.7
Table 2 Mechanical properties of the as-extruded AXM alloy sheets with different Ce contents
Sample
a / nm
c / nm
c / a
AXM
0.321424
0.521882
1.62365
AXM + 0.05Ce
0.321317
0.521645
1.62346
AXM + 0.5Ce
0.321447
0.521800
1.62328
Table 3 c / a values obtained by the XRD data of the AXM, AXM + 0.05Ce, and AXM + 0.5Ce alloys
Fig.7 EBSD analyses of the as-extruded AXM (a-e), AXM + 0.05Ce (f-j), and AXM + 0.5Ce (k-o) alloy sheets (a, f, k) band contrast maps of the as-extruded AXM (a), AXM + 0.05Ce (f), and AXM + 0.5Ce (k) alloy sheets, respectively (b, g, l) EBSD images of square regions in Figs.7a (b), f (g), and k (l), respectively (c, h, m) (0002) PFs with scatter data of square regions in Figs.7a (c), f (h), and k (m), respectively (d, i, n) inverse pole figures (IPFs) with scatter data along ED of square regions in Figs.7a (d), f (i), and k (n), respectively (e, j, o) basal pole tilt distribution maps of square regions in Figs.7a (e), f (j), and k (o), respectively
Fig.8 (0002) PFs and corresponding IPFs along ED of grain size of the as-extruded AXM (a1-a4), AXM + 0.05Ce (b1-b4), and AXM + 0.5Ce (c1-c4) alloy sheets (a1-c1) all grains (a2-c2) grain size < 10 μm (a3-c3) grain size 10-25 μm (a4-c4) grain size > 25 μm
Fig.9 Schmid factor (SF) distribution maps of (0001)<110> basal slip of the as-extruded AXM (a, b), AXM + 0.05Ce (c, d), and AXM + 0.5Ce (e, f) alloy sheets along ED (a, c, e) and TD (b, d, f)
Fig.10 Average Schmid factor ratios along TD and ED of (0001)<110> basal slip of the as-extruded AXM, AXM + 0.05Ce, and AXM + 0.5Ce alloy sheets
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