Deformation behavior of Mg-Y-Ni alloys containing different volume fraction of LPSO phase during tension and compression through in-situ synchrotron diffraction
Deformation behavior of Mg-Y-Ni alloys containing different volume fraction of LPSO phase during tension and compression through in-situ synchrotron diffraction
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DOI：
10.1016/j.jma.2023.01.013
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发表时间：
2023-02
影响因子：
17.6
通讯作者：
S.Z. Wu;Y. Chi;G. Garcés;X.H. Zhou;H. Brokmeier;X. Qiao;M. Y. Zheng
中科院分区：
文献类型：
--
作者：
S.Z. Wu;Y. Chi;G. Garcés;X.H. Zhou;H. Brokmeier;X. Qiao;M. Y. Zheng
采用原位同步衍射研究了不同体积分数长周期有序堆积相（LPSO）挤压态Mg-Y-Ni合金在拉伸和压缩过程中的变形行为。结合变形机理，探讨了合金的微观屈服、宏观屈服、拉压不对称和应变硬化行为。微屈服以拉伸状态下动态再结晶（DRXed）晶粒的基底滑移为主，压缩状态下非动态再结晶（非DRXed）晶粒的扩展孪晶为主。宏观屈服时，非DRXed晶粒在拉伸下仍处于弹性变形状态，而DRXed晶粒在压缩下的基底滑移被激活。同时，LPSO相仍然保持弹性变形，但可以承受更多的载荷，因此，硬LPSO相的体积分数越高，合金的拉伸/压缩宏观屈服强度越高。得益于非drxed晶粒的低体积分数以及LPSO和γ′相对扩展孪晶的延迟效应，挤压态合金表现出优异的拉伸-压缩对称性。当LPSO相的体积分数达到~ 50%时，拉伸-压缩不对称被逆转，这是由于LPSO相在压缩时比在拉伸时更强。拉伸应变硬化行为以位错滑移为主，而压缩应变硬化的主要机制则随着LPSO相体积分数的增加，由α-Mg晶粒的孪晶转变为LPSO相的扭结。扭结活化导致压缩应变硬化速率恒定在~ 2500 MPa，显著高于拉伸应变硬化速率。
The deformation behavior of the as-extruded Mg-Y-Ni alloys with different volume fraction of long period stacking ordered (LPSO) phase during tension and compression was investigated byin-situsynchrotron diffraction. The micro-yielding, macro-yielding, tension-compression asymmetry and strain hardening behavior of the alloys were explored by combining with deformation mechanisms. The micro-yielding is dominated by basal slip of dynamic recrystallized (DRXed) grains in tension, while it is dominated by extension twinning of non-dynamic recrystallized (non-DRXed) grains in compression. At macro-yielding, the non-DRXed grains are still elastic deformed in tension and the basal slip of DRXed grains in compression are activated. Meanwhile, the LPSO phase still retains elastic deformation, but can bear more load, so the higher the volume fraction of hard LPSO phase, the higher the tensile/compressive macro-yield strength of the alloys. Benefiting from the low volume fraction of the non-DRXed grains and the delay effect of LPSO and γ′ phases on extension twinning, the as-extruded alloys exhibit excellent tension-compression symmetry. When the volume fraction of LPSO phase reaches ∼50%, tension-compression asymmetry is reversed, which is due to the fact that the LPSO phase is stronger in compression than in tension. The tensile strain hardening behavior is dominated by dislocation slip, while the dominate mechanism for compressive strain hardening changes from twinning in the α-Mg grains to kinking of the LPSO phase with increasing volume fraction of LPSO phase. The activation of kinking leads to the constant compressive strain hardening rate of ∼2500 MPa, which is significantly higher than the tensile strain hardening rate.