Production of Nanostructured Fasteners with High Shear and Fatigue Strength for Use in Aircraft

Multi-axis forging (MAF) and cyclic heat treatment are among the most widely used and easy to apply grain refinement methods. In this study, microalloyed steel samples were first subjected to MAF treatments at 880° C. Microstructural analysis showed that the average grain size, which was 13.2 µm initially, decreased to 11.2 µm application of the MAF. As a second grain refinement technique, cyclic heat treatment was used. Samples were subjected to 1, 3, 5, 7 and 10 cyclic quenching. With this method, it was observed that the average grain size decreased to 2,3 µm. The mechanical tests showed that second MAF process increased the yield and tensile strength of the material about %16 while decrease the elongation only by %2. These tests also presented cyclic quenching increase tensile strength of the samples after first application.