In Situ Reaction Kinetics and Microstructure Evolution in Preparing Particle-Containing Copper Alloys by Mechanical Alloying

To improve alloy properties and the distribution level of TiB 2 particles in the alloy matrix, mechanical alloying was used to prepare the Cu-TiB 2 alloy. But even after long-time ball milling, the in situ reaction between Cu-B and Cu-Ti alloy powders still cannot be observed in the whole process. The kinetics of the in situ reaction during high-temperature heat treatment was first investigated and led to the following results. With the increase of heat-treatment time t or diffusion depth X , both the moving speed Δ x /Δ t of reaction front edge and nucleation rate Z ( x ) of TiB 2 particles decrease at a fast rate and finally stabilize at a very low level. The falling rate of moving speed Δ x /Δ t increases with the decrease of temperature. Although the C Ti ′ value of the Ti element gives a poor effect on the moving speed Δ x /Δ t , it significantly affects the nucleation rate of TiB 2 particles, and its falling rate increases with a decreasing C Ti ′ value. And for the same diffusion depth X and C Ti ′, the nucleation rate of TiB 2 decreases with increasing the heat-treatment temperature. These results were verified by the microstructure change after the heat treatments at temperatures of 773 K, 973 K, and 1173 K (500 °C, 700 °C, and 900 °C), respectively. Finally, the best combination of ball-milling and heat-treatment conditions was obtained.