Mg-Y-Ni alloys with different second phases were designed by changing Y/Ni atomic ratio from 1.5 to 0.5.The microstructure and mechanical properties of as-cast and as-extruded alloys were investigated.The as-cast Mg-Y...Mg-Y-Ni alloys with different second phases were designed by changing Y/Ni atomic ratio from 1.5 to 0.5.The microstructure and mechanical properties of as-cast and as-extruded alloys were investigated.The as-cast Mg-Y-Ni alloy with Y/Ni ratio of 1.5 is composed ofα-Mg and long period stacking ordered(LPSO)phase.When Y/Ni ratio is equal to 1,nanoscale lamellarγ’phase and eutectic Mg2Ni phase are formed in addition to LPSO phase.As Y/Ni ratio decreases further,the amount of eutectic Mg2Ni phase increases,while the amount of LPSO phase decreases.After extrusion,the LPSO andγ’phases are distributed along the extrusion direction,while eutectic Mg2Ni phase is broken and dispersed in the as-extruded alloys.LPSO phase and Mg2Ni phase in the alloys promote dynamic recrystallization(DRX)during extrusion,whileγ’phase inhibits DRX.Consequently,the Mg96Y2Ni2(at.%)alloy with LPSO phase andγ’phase as the main second phases shows the strongest basal texture after extrusion.The tensile yield strength of the as-extruded Mg-Y-Ni alloys increases first and then decreases with decreasing Y/Ni ratio.The as-extruded Mg96Y2Ni2(at.%)alloy with Y/Ni=1 exhibits excellent mechanical properties with tensile yield strength of 465 MPa,ultimate tensile strength of 510 MPa and elongation to failure of 7.2%,which is attributed to the synergistic effect of bulk LPSO phase and nanoscaleγ’phase.展开更多
The structures and properties of Y-substituted Mg<sub>2</sub>Ni alloys and the corresponding hydrides are investigated by a first-principles plane-wave pseudopotential method within density functional theo...The structures and properties of Y-substituted Mg<sub>2</sub>Ni alloys and the corresponding hydrides are investigated by a first-principles plane-wave pseudopotential method within density functional theory. Results show that Mg<sub>2</sub>Ni has the best structural stability when Y atom occupies the Mg(6f) lattice sites. The calculated enthalpies of formation for Mg<sub>2</sub>Ni, Mg<sub>2</sub>NiH<sub>4</sub> and Mg<sub>15</sub>YNi<sub>8</sub>H<sub>32</sub> are -51.612, -64.667 and -62.554 kJ/mol, respectively. It is implied that the substitution of Y alloying destabilizes the stability of the hydrides. Moreover, the dissociated energies of H atoms are decreased significantly, indicating that Y alloying benefits the improvement of the dehydrogenating properties of Mg<sub>2</sub>Ni hydrides. The calculation and analysis of the electronic structures suggest that there is a stronger interaction between H and Ni atoms than the interaction between H and Mg atoms in Mg<sub>2</sub>NiH<sub>4</sub>. However, the Ni-H bond is weakened by the substitution of Y. Therefore, the substitution is an effective technique to decrease the structural stability of the hydrides and benefit for hydrogen storage.展开更多
Yttrium （Y） has been used as the partial substitution element for lanthanum （La） to improve the electrochemical kinetic performances of La-Mg-Ni-based hydrogen storage alloys. Lao.80-xYxMg0.20Ni2.85Mn0.10Coo.55Al0...Yttrium （Y） has been used as the partial substitution element for lanthanum （La） to improve the electrochemical kinetic performances of La-Mg-Ni-based hydrogen storage alloys. Lao.80-xYxMg0.20Ni2.85Mn0.10Coo.55Al0.10 （x=0.00, 0.05 and 0.10） alloys were prepared by the inductive melting technique. The alloys were composed of LaNi5 and （La,Mg）2Ni7 phases, the introduction of Y promoted the formation of （La,Mg）2Ni7 phase, and thus the Y-substituted alloy electrodes exhibited higher discharge capacities. Y substitution was also found to be effective to improve the discharge kinetics of the alloy electrodes. When the Y content x increased from 0.00 to 0.10, the high-rate dischargeability of the alloy electrodes at a discharge current density of 1800 mA/g （HRDl800） in- creased from 23.6% to 39.7% at room temperature. In addition, the measured HRD1800 showed a linear dependence on both the ex- change current density and the hydrogen diffusion coefficient at different temperatures, respectively.展开更多
通过粉末冶金烧结方法制备A2B7型含镁La_(1.9-x)Y_(x)Mg_(0.1)Ni_(6.48)Mn_(0.32)Al_(0.2)(x=0~1.8)和无镁La_(0.8)Y_(1.2)Ni_(6.48)Mn_(0.32)Al_(0.2)合金,研究了掺杂Mg条件下Y元素对合金物相组成、晶体结构和电化学性能的影响规律和...通过粉末冶金烧结方法制备A2B7型含镁La_(1.9-x)Y_(x)Mg_(0.1)Ni_(6.48)Mn_(0.32)Al_(0.2)(x=0~1.8)和无镁La_(0.8)Y_(1.2)Ni_(6.48)Mn_(0.32)Al_(0.2)合金,研究了掺杂Mg条件下Y元素对合金物相组成、晶体结构和电化学性能的影响规律和协同作用。结果表明,适量增加Y含量有助于含Mg合金形成2H-Ce_(2)Ni_(7)型相单相组织,Mg与Y原子优先占据2H-Ce_(2)Ni_(7)型主相中的[A_(2)B_(4)]结构单元,随Y含量x增加,2H-Ce_(2)Ni_(7)型主相晶胞参数a,c,V_(cell)及[A_(2)B_(4)]与[AB_(5)]单元结构的体积差ΔV_(d)均逐渐减小,但无镁及含镁x=1.8合金的2H-Ce_(2)Ni_(7)型主相具有相对较高的V_(cell)和ΔV_(d)值。合金的放氢PCT曲线特征和电化学性能与掺Mg,Y含量及ΔV_(d)关系密切,含镁合金的电化学性能优于无镁合金,其中含镁x=1.0~1.2合金具有较小的ΔV_(d)和最佳的电化学性能,该电极放电容量达到最大值375 m Ah·g^(-1),经100周充放电循环后的容量保持率S100为91%,放电电流密度为900 mA·g^(-1)时的高倍率放电性能HRD_(900)为80%。通过掺Mg和优化Y含量可明显改善La-Y-Ni系A_(2)B_(7)型合金的电化学性能。展开更多
基金the National Key Research and Development Program of China(No.2016YFB0301102)。
文摘Mg-Y-Ni alloys with different second phases were designed by changing Y/Ni atomic ratio from 1.5 to 0.5.The microstructure and mechanical properties of as-cast and as-extruded alloys were investigated.The as-cast Mg-Y-Ni alloy with Y/Ni ratio of 1.5 is composed ofα-Mg and long period stacking ordered(LPSO)phase.When Y/Ni ratio is equal to 1,nanoscale lamellarγ’phase and eutectic Mg2Ni phase are formed in addition to LPSO phase.As Y/Ni ratio decreases further,the amount of eutectic Mg2Ni phase increases,while the amount of LPSO phase decreases.After extrusion,the LPSO andγ’phases are distributed along the extrusion direction,while eutectic Mg2Ni phase is broken and dispersed in the as-extruded alloys.LPSO phase and Mg2Ni phase in the alloys promote dynamic recrystallization(DRX)during extrusion,whileγ’phase inhibits DRX.Consequently,the Mg96Y2Ni2(at.%)alloy with LPSO phase andγ’phase as the main second phases shows the strongest basal texture after extrusion.The tensile yield strength of the as-extruded Mg-Y-Ni alloys increases first and then decreases with decreasing Y/Ni ratio.The as-extruded Mg96Y2Ni2(at.%)alloy with Y/Ni=1 exhibits excellent mechanical properties with tensile yield strength of 465 MPa,ultimate tensile strength of 510 MPa and elongation to failure of 7.2%,which is attributed to the synergistic effect of bulk LPSO phase and nanoscaleγ’phase.
基金the financial supports from the National Natural Science Foundation of China(Nos.52175321,52101138)Start-up Fund from Huazhong University of Science and Technology,China(Nos.3004110125,3004110142)+4 种基金State Key Lab of Advanced Metals and Materials,China(No.2020-Z01)State Key Laboratory for Mechanical Behavior of Materials,China(No.20202205)State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,China(No.32015001)Guangdong Basic and Applied Basic Research Foundation,China(No.2020A1515110531)Natural Science Foundation of Hubei Province,China(No.2020CFB259)。
文摘The structures and properties of Y-substituted Mg<sub>2</sub>Ni alloys and the corresponding hydrides are investigated by a first-principles plane-wave pseudopotential method within density functional theory. Results show that Mg<sub>2</sub>Ni has the best structural stability when Y atom occupies the Mg(6f) lattice sites. The calculated enthalpies of formation for Mg<sub>2</sub>Ni, Mg<sub>2</sub>NiH<sub>4</sub> and Mg<sub>15</sub>YNi<sub>8</sub>H<sub>32</sub> are -51.612, -64.667 and -62.554 kJ/mol, respectively. It is implied that the substitution of Y alloying destabilizes the stability of the hydrides. Moreover, the dissociated energies of H atoms are decreased significantly, indicating that Y alloying benefits the improvement of the dehydrogenating properties of Mg<sub>2</sub>Ni hydrides. The calculation and analysis of the electronic structures suggest that there is a stronger interaction between H and Ni atoms than the interaction between H and Mg atoms in Mg<sub>2</sub>NiH<sub>4</sub>. However, the Ni-H bond is weakened by the substitution of Y. Therefore, the substitution is an effective technique to decrease the structural stability of the hydrides and benefit for hydrogen storage.
基金Project supported by the National Natural Science Foundation of China(51171165,21303157)the Natural Science Foundation of Hebei Province(B2012203027,B2012203104 and B2014203114)
文摘Yttrium （Y） has been used as the partial substitution element for lanthanum （La） to improve the electrochemical kinetic performances of La-Mg-Ni-based hydrogen storage alloys. Lao.80-xYxMg0.20Ni2.85Mn0.10Coo.55Al0.10 （x=0.00, 0.05 and 0.10） alloys were prepared by the inductive melting technique. The alloys were composed of LaNi5 and （La,Mg）2Ni7 phases, the introduction of Y promoted the formation of （La,Mg）2Ni7 phase, and thus the Y-substituted alloy electrodes exhibited higher discharge capacities. Y substitution was also found to be effective to improve the discharge kinetics of the alloy electrodes. When the Y content x increased from 0.00 to 0.10, the high-rate dischargeability of the alloy electrodes at a discharge current density of 1800 mA/g （HRDl800） in- creased from 23.6% to 39.7% at room temperature. In addition, the measured HRD1800 showed a linear dependence on both the ex- change current density and the hydrogen diffusion coefficient at different temperatures, respectively.
文摘通过粉末冶金烧结方法制备A2B7型含镁La_(1.9-x)Y_(x)Mg_(0.1)Ni_(6.48)Mn_(0.32)Al_(0.2)(x=0~1.8)和无镁La_(0.8)Y_(1.2)Ni_(6.48)Mn_(0.32)Al_(0.2)合金,研究了掺杂Mg条件下Y元素对合金物相组成、晶体结构和电化学性能的影响规律和协同作用。结果表明,适量增加Y含量有助于含Mg合金形成2H-Ce_(2)Ni_(7)型相单相组织,Mg与Y原子优先占据2H-Ce_(2)Ni_(7)型主相中的[A_(2)B_(4)]结构单元,随Y含量x增加,2H-Ce_(2)Ni_(7)型主相晶胞参数a,c,V_(cell)及[A_(2)B_(4)]与[AB_(5)]单元结构的体积差ΔV_(d)均逐渐减小,但无镁及含镁x=1.8合金的2H-Ce_(2)Ni_(7)型主相具有相对较高的V_(cell)和ΔV_(d)值。合金的放氢PCT曲线特征和电化学性能与掺Mg,Y含量及ΔV_(d)关系密切,含镁合金的电化学性能优于无镁合金,其中含镁x=1.0~1.2合金具有较小的ΔV_(d)和最佳的电化学性能,该电极放电容量达到最大值375 m Ah·g^(-1),经100周充放电循环后的容量保持率S100为91%,放电电流密度为900 mA·g^(-1)时的高倍率放电性能HRD_(900)为80%。通过掺Mg和优化Y含量可明显改善La-Y-Ni系A_(2)B_(7)型合金的电化学性能。
