The complex interaction between microstructural features and crack evolution during cyclic testing in heat-treated Al-Si-Mg-Cu cast alloys

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:825

Article

Bogdanoff, Toni¹  Lattanzi, Lucia^1,2  Merlin, Mattia²  Ghassemali, Ehsan¹  Jarfors, Anders E. W.¹  Seifeddine, Salem¹ 

[1] Jonkoping Univ, Dept Mat & Mfg, Box 1026, S-55111 Jonkoping, Sweden

[2] Univ Ferrara, Dept Engn, Via Giuseppe Saragat 1, I-44122 Ferrara, Italy

关键词: Aluminium alloys;    Electron microscopy;    Characterisation;    Casting methods;    Fatigue;   

DOI  :  10.1016/j.msea.2021.141930

来源: Elsevier

【 摘 要 】

The study aimed to investigate crack initiation and propagation at the micro-scale in heat-treated Al-7Si-Mg cast alloys with different copper (Cu) contents. In-situ cyclic testing in a scanning electron microscope coupled with electron back-scattered diffraction and digital image correlation was used to evaluate the complex interaction between the crack path and the microstructural features. The three-nearest-neighbour distance of secondary particles was a new tool to describe the crack propagation in the alloys. The amount of Cu retained in the alpha-Al matrix after heat treatment increased with the Cu content in the alloy and enhanced the strength with a slight decrease in elongation. During cyclic testing, the two-dimensional (2D) crack path appeared with a mixed propagation, both trans- and inter-granular, regardless of the Cu content of the alloy. On fracture surfaces, multiple crack initiation points were detected along the thickness of the samples. The debonding of silicon (Si) particles took place during crack propagation in the Cu-free alloy, while cracking of Si particles and intermetallic phases occurred in the alloy with 3.2 wt% Cu. Three-dimensional tomography using focused ion beam revealed that the improved strength of the alpha-Al matrix changes the number of cracked particles ahead of the propagating crack with Cu concentration above 1.5 wt%.

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