Microstructure and texture evolution in Mg/Nb layered materials made by accumulative roll bonding
Microstructure and texture evolution in Mg/Nb layered materials made by accumulative roll bonding
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DOI：
10.1016/j.ijplas.2019.08.015
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发表时间：
2020-02-01
影响因子：
9.8
通讯作者：
Knezevic, Marko
中科院分区：
文献类型：
--
作者：
Savage, Daniel J.;Beyerlein, Irene J.;Knezevic, Marko
在这项工作中，结合了两种完全六角镁锂合金（MG-4LI和MG-5LI WT％）和纯niobium（NB）的层状复合材料板是通过累积滚动键（ARB）制造的。由于超过两个真正的菌株的极高紧张，单个层被完善至200 mu m。与应变相结合相之间的强度差异足够低，可以促进粘结而没有不稳定性。另外，通过中间退火增强了变形的同质性，尤其是对于MG-XLI阶段。衍射方法和多晶建模用于研究每个随后的ARB通行证后各个相的微观结构和纹理演变。通过电子反向衍射和中子衍射的表征揭示了在MG-XLI相中，相位的显着变化和阶段的纹理变化，几乎没有变形。确定和讨论谷物形态的演变以及跨越ARB和退火的层的晶粒数量。为了将纹理演变与处理过程中的基于滑动的变形机制联系起来，开发了两相MG-4LI/NB复合材料的多尺度多晶模型，其中包括一种相对方向性合规性（RDC）方法，可以考虑到阶段的相互作用，从而使基于多个Slip and ing notb of Moulty Slip n of Moulty Slim n of Moulty notb in n of Moulty notb of Moulty notb in n of Moulty note note note note and note note notem notem in n of Moulty notb。该模型表明，在ARB周期期间MG-4LI相的变形是由更多的基础<a>和比以前报道的MG-4LI滚动的棱柱形<a>，Pyramidal <c + a>越来越少的棱柱形<a>和twinning的。实验纹理不能完全用晶粒形状来解释，并且晶粒尺寸较小，需要按预期的预期金字塔和棱镜滑动性增加。该模型与测量结果一致，预测MG-4LI相的C轴从板的正常方向向滚动方向倾斜，并且强gamma纤维和异常弱的A纤维应在NB中发育，并具有较大的ARB ARB扭伤MG-XLI/NB复合材料。
In this work, lamellar composite sheets combining one of two fully hexagonal magnesium-lithium alloys (Mg-4Li and Mg-5Li wt%) and pure niobium (Nb) are manufactured via accumulative roll bonding (ARB). With extreme straining of over two true strain, the individual layers were refined to 200 mu m. The strength differential between co-deforming phases with strain is characterized to be low enough to facilitate bonding without instabilities. Additionally, homogeneity in deformation was enhanced by intermediate annealing, especially for the Mg-xLi phase. Diffraction methods and polycrystal modeling are employed to study the microstructure and texture evolution of the individual phases after each subsequent ARB pass. Characterization by electron backscatter diffraction and neutron diffraction reveals substantial changes in microstructure and texture in both phases and very little deformation twinning in the Mg-xLi phase. Evolution of grain morphology and the number of grains that span a layer with ARB and annealing are determined and discussed. To link texture evolution to slip-based deformation mechanisms during the processing, a multiscale polycrystalline model of the two-phase Mg-4Li/Nb composite was developed, which included a relative directional compliance (RDC) method to account for anisotropic interactions in the phases, allowing appropriate slip sensitivity to dislocation density based hardening on the multiple slip modes in Mg-4Li and in Nb. The model indicates that the deformation of the Mg-4Li phase during ARB cycles was accommodated by more basal < a > and progressively smaller amounts of prismatic < a > , pyramidal < c + a > , and twinning than previously reported for rolling of Mg-4Li. The experimental textures cannot be entirely explained by grain shape and an increase in pyramidal and prismatic slip resistance are required as expected with a small grain size. Consistent with measurements, the model predicts that c-axis of the Mg-4Li phase tilts from the sheet's normal direction towards the rolling direction, and that the strong gamma-fiber and the unusually weak a-fiber should develop in Nb with large ARB straining of the Mg-xLi/Nb composites.