Achieving high strength and ductility in a heterogeneous bimodal grain structured TiC/AZ61 magnesium nanocomposites via powder metallurgy
Achieving high strength and ductility in a heterogeneous bimodal grain structured TiC/AZ61 magnesium nanocomposites via powder metallurgy
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DOI：
10.1016/j.msea.2022.144344
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发表时间：
2022-11
期刊：
影响因子：
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通讯作者：
Lingling Fan;Mingyang Zhou;Yuwenxi Zhang;H. Dieringa;Xiaoying Qian;Ying Zeng;Xianwen Lu;Y. Huang-Y
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文献类型：
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作者：
Lingling Fan;Mingyang Zhou;Yuwenxi Zhang;H. Dieringa;Xiaoying Qian;Ying Zeng;Xianwen Lu;Y. Huang-Y
为了同时提高纳米颗粒增强镁基复合材料的强度和塑性，制备了由TiC稀疏粗晶（CG）带和富TiC细晶（FG）带组成的TiC/AZ 61纳米复合材料。通过调节球磨时间，改变不同形貌粉末的比例，可以优化CG带的分数。结果表明，球磨12 h后，复合材料开始形成异质双峰晶粒（HBG）结构。随着球磨时间从12 h进一步增加到30 h，球形粉末的比例下降，CG带的体积分数从48.4%下降到11.7%。球磨20 h后，添加质量分数为25%（体积分数）的CG带的复合材料具有优异的综合力学性能（抗拉强度为417 MPa，屈服强度为323 MPa，伸长率为10.2%）。此外，HBG-20 h复合材料在极限拉伸强度下具有显著的附加强化，这是由于粗晶带内存在几何必需位错（GNDs），这是由CG带和FG区之间的机械不相容性引起的。这种位错在HBG-20 h复合材料中提供了最佳的背应力加工硬化，这是由于其合适的CG带分数（1.25体积%），有助于高应变硬化。
Heterogeneous TiC/AZ61 nanocomposites, consisting of TiC-rare coarse grain (CG) bands and TiC-rich fine grain (FG) zones, were fabricated to simultaneously improve the strength and ductility of nanoparticles reinforced Mg matrix composites. The fraction of CG bands could be optimized by adjusting the mechanical ball milling time to change the proportion of powders with different morphologies. It was found that composites began to form a heterogeneous bimodal grain (HBG) structure after 12 h ball milling. With further increasing the ball milling time from 12 h to 30 h, the proportion of spherical powder decreased, the volume fraction of CG bands decreased from 48.4% to 11.7%. Excellent comprehensive mechanical properties (ultimate tensile strength: 417 MPa, yield strength: 323 MPa, and elongation: 10.2%) were achieved for the composite with ∼25 vol% CG bands after 20 h of ball milling. Moreover, the HBG-20 h composite had significant additional strengthening at ultimate tensile strength owing to the existence of geometrically necessary dislocations (GNDs) inside the coarse grain bands, which were introduced by mechanical incompatibility between the CG band and FG zone. Such dislocations provided optimum back-stress work hardening at the HBG-20 h composite due to its suitable CG band fraction (∼ 25 vol%), contributing to the high strain-hardening.