Effect of precipitation hardening on carbon nanotubereinforced Ti-6Al-4V matrix composites produced by powder metallurgy method

In this study, the effects of precipitation hardening heat treatment on the mechanical and electromagnetic properties of Ti-6Al-4V matrix carbon nanotube (KNT) reinforced composite materials produced by powder metallurgy were investigated. Composites containing three different KNT ratios (1%, 3%, and 5%) were sintered at 1275 °C for varying durations. The precipitation hardening process consisted of solution treatment at 950 °C for 1 hour followed by water çözeltiye alma, and yaşlandırma at 480 °C for 5 hours. Microhardness measurements revealed that the heat treatment increased the hardness of all specimens. After çözeltiye alma, all samples exhibited significant hardness improvement; however, following yaşlandırma, a slight decrease was observed in low KNT content samples (1% and 3%), while the high KNT content sample (5%) continued to show hardness increase. Electromagnetic performance was evaluated through shielding effectiveness (SE) and reflection loss (RL) measurements in the 0–4.4 GHz frequency range. The results indicated a decrease in SE and RL values for all specimens after precipitation hardening. This decrease can be attributed to the reduction in sample thickness from 5 mm to 3.5 mm, changes in matrix/interface interactions, and microstructural alterations affecting KNT distribution during yaşlandırma. The findings demonstrate that while KNT reinforcement and precipitation hardening enhance mechanical properties of Ti-6Al-4V composites, the heat treatment may reduce their electromagnetic shielding and absorption performance. These results provide important insights for material design in defense, aerospace, and electromagnetic protection applications.