Research On Microstructure Evolution And Mechanical Properties Of GH5188 Foil

Cold rolled GH5188 foil (0.12mm thickness) was studied in the present work. In view of the materials in three states: cold-rolled, welding process, fatigue tested servicing in a simple simulation condition, researches were made on their microstructures and mechanical properties with some modern analysis and detection methods to provide a theoretical basis for the design, the safe use and test of metal honeycomb structure. The researches included: the microstructures of the GH5188 foil, phase structure and sub-structure analysis, the deformation behavior of tensile properties, hardness test and three-point bending fatigue test.The results showed that the microstructures of the cold-rolled GH5188 foil were mainlyγphase in the matrix and precipitated phases in grains and on the boundary. The average grain size of the state one specimen was 10μm, the internal structure was compact and uniform, and a large number of twin crystal existed while granular precipitate was little. However, mass M2C and M6C precipitates and dislocation existed in both state two and state three specimens. Microstructure close to the solder was tend to be widmanstatten, but in the areas away from the solder, it remained the state one specimen, certain changes only occured on the boundary. There were a lot of twin crystals in the structure of the three state specimens. It showed that twin crystal growed up in the way of wrong layer overlay and the steps formed at the rear.So the type of the twin crystal is annealing twin.GH5188 foil's tensile fracture surface showed that the overall fracture mode was ductile fracture, and dimples distribute on most of the fracture surface, brittle fracture only occured in few defective regions. The mechanical properties at room temperature of the state one specimen were outstanding, its tensile strength was 1254MPa and extension rate was 41.0%. Compared to the state one foil, the extension rate of the state two specimen was only 4.9% because of the brittle fracture of the solder, and there was a slight decline in tensile properties after tested on three-point bending fatigue, and its fracture mode was both ductile fracture and brittle fracture.The hardness of the foil in different states was analyzed and contrasted. The results showed that the process, the stress and temperature all had a certain influence on the micro hardness of the foil plate. Three-point bending fatigue tests detected that honeycomb sandwich panel could withstand a maximum static load of 1100N, and its fatigue life under high temperature was higher than room temperature. The main reason was that high temperature made the slip systems inside the material easy to start, and reduced the trend of dislocation pileup and inside defects.