Optimized Process Design for Uniform Microstructure and High-Strength Ti-6Al-4 V Alloy Fasteners in Aerospace Applications

Abstract

Ti-6Al-4V alloy is extensively used in the aerospace industry due to its high specific strength and excellent corrosion resistance. However, its limited workability makes the conventional manufacturing of aerospace fasteners complex, involving multiple steps such as cutting, rolling, drawing, heading, and heat treatment. In this study, an innovative warm-forging technique using a 1-die 2-blow system was developed to enable high-efficiency bulk production of fasteners with a uniform microstructure and enhanced strength. Finite element simulation was employed to optimize the forging temperature, ensuring effective material flow and minimal defects. Subsequently, the forged bolts were heat treated under optimized conditions to obtain a fine equiaxed alpha-phase. The heat treatment parameters including solution temperature (degrees C), solution time (min), aging temperature (degrees C), and aging time (h) were optimized using an artificial neural network (ANN) model to maximize strength (kN). The ANN predicted an optimal heat treatment condition of 927 degrees C for 17 min (solution treatment) followed by aging at 482 degrees C for 4 h. The alpha-phase size in the as-forged and optimally heat-treated Ti-6Al-4 V bolts was 4 +/- 1.2 mu m and 3.51 +/- 0.97 mu m, respectively. The resulting aerospace-grade fasteners demonstrated a favorable combination of high strength and ductility, confirming the effectiveness of the proposed process.