研究目的
To study the influence of the microstructural gradient on the strain localization in repaired structures, specifically focusing on the interface between the base material and the repaired region.
研究成果
The study highlights the strong spatial gradient of microstructure in Inconel 718 components repaired using Laser Cladding technology. The microstructural gradient induces a plastic strain localization in the cladded region, explained on the large scale by grain size effect using the Hall-Petch law. The variation of the plastic strain distribution at a smaller scale involves more complex phenomena and interactions.
研究不足
The study is limited by the 2D observations on a 3D structure, the use of Inconel 718 without precipitation hardening, and the inability to observe the strain pattern induced around Laves phase due to stress concentration with the current DIC precision.
1：Experimental Design and Method Selection
In-situ SEM tensile tests completed by EBSD observations of the microstructure in the interface neighborhood between the base material and the repaired region. Digital Image Correlation methods were used to monitor the evolution of the local plastic strain distribution at the grain level until failure.
2：Sample Selection and Data Sources
Repaired specimens of Inconel 718, a nickel alloy, were used. The substrate was a wrought Inconel 718 plate, and the powder used for Laser Cladding was Inconel 718 with particle diameter between 45-105 μm.
3：List of Experimental Equipment and Materials
FEI Quanta 600 FEG-ESEM for SEM and EBSD analysis, Gatan PECS II machine for ion polishing, Innovastest Falcon 400 for Vickers hardness measurements, homemade tensile machine for SEM in-situ tests.
4：Experimental Procedures and Operational Workflow
The surface of the samples was mechanically polished up to 1 μm before ion polishing. A gold grid with a 3 μm pitch was deposited by electro-lithography on the face view of the specimen in the interface area. SEM in-situ tests were displacement-controlled at 0.002 mm/s with several loading steps.
5：Data Analysis Methods
Digital Image Correlation software Correlation Manual Value was used to compute strain maps. The strain maps were superimposed to the grain maps obtained by EBSD. Detection of the grain contours was conducted with a Matlab code.
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