Micro-strain Evolution and Toughening Mechanisms in a Trimodal Al-Based Metal Matrix Composite
Micro-strain Evolution and Toughening Mechanisms in a Trimodal Al-Based Metal Matrix Composite
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DOI：
10.1007/s11661-014-2729-8
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发表时间：
2015-01
期刊：
影响因子：
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通讯作者：
Yuzheng Zhang;T. Topping;Hanry Yang;E. Lavernia;J. Schoenung;S. Nutt
中科院分区：
文献类型：
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作者：
Yuzheng Zhang;T. Topping;Hanry Yang;E. Lavernia;J. Schoenung;S. Nutt
基于 AA（铝合金）5083（Al-4.4Mg-0.7Mn-0.15Cr wt pct）的三峰金属基复合材料（MMC）是通过低温研磨粉末，然后使用两个连续的双模动态锻造压实混合粉末和陶瓷颗粒来合成的。微观结构由 66.5% 超细晶粒 (UFG) 区域、30% 粗晶粒 (CG) 区域和 3.5% 增强碳化硼颗粒组成。与传统 AA 5083 (242 MPa) 相比，该微观结构具有高拉伸屈服强度 (581 MPa)，与 100% UFG Al MMC 相比，延展性更高。使用原位扫描电子显微镜微拉伸试验研究了异质结构的变形行为以及CG区域对裂纹扩展的影响。使用数字图像相关测量的微应变演化显示了 CG 区域的早期塑性应变局部化。由于 CG/UFG 界面处的应变不匹配而产生的微空隙是裂纹萌生的原因。 CG区域增韧是通过塑性诱导裂纹闭合和不连续微裂纹的区域屏蔽来实现的。然而，这些增韧机制并没有有效抑制其脆性行为。需要进一步优化 CG 分布（间距和形态）以达到结构应用所需的韧性水平。
A trimodal metal matrix composite (MMC) based on AA (Al alloy) 5083 (Al-4.4Mg-0.7Mn-0.15Cr wt pct) was synthesized by cryomilling powders followed by compaction of blended powders and ceramic particles using two successive dual mode dynamic forgings. The microstructure consisted of 66.5 vol pct ultrafine grain (UFG) region, 30 vol pct coarse grain (CG) region and 3.5 vol pct reinforcing boron carbide particles. The microstructure imparted high-tensile yield strength (581 MPa) compared to a conventional AA 5083 (242 MPa) and enhanced ductility compared to 100 pct UFG Al MMC. The deformation behavior of the heterogeneous structure and the effects of CG regions on crack propagation were investigated usingin situscanning electron microscopy micro-tensile tests. The micro-strain evolution measured using digital image correlation showed early plastic strain localization in CG regions. Micro-voids due to the strain mismatch at CG/UFG interfaces were responsible for crack initiation. CG region toughening was realized by plasticity-induced crack closure and zone shielding of disconnected micro-cracks. However, these toughening mechanisms did not effectively suppress its brittle behavior. Further optimization of the CG distribution (spacing and morphology) is required to achieve toughness levels required for structural applications.