The growth restriction effect of TiCN nanoparticles on Al-Cu-Zr alloys via ultrasonic treatment

Ex situ and in situ synchrotron X-radiography study on Al-Cu-Zr alloys with addition of Al-5Ti-1B and TiCN nanoparticles (TiCN(np)) were carried out at different cooling rates. Al-Zr alloy can be effectively refined by TiCN(np) via Ultrasonic treatment as compared with Al-5Ti-1B which has Zr poisoning effect. The influence of cooling rate on the nucleation and growth of grains have been studied quantitatively. The results show that the grain size was decreased and the growth rate was increased with the increasing of cooling rate. At the same cooling rate, the grain size with addition of 0.5% TiCN(np) was smaller than that with the same addition of Al-5Ti-1B. The blocking factor [Formula: see text] of TiCN(np) decreases with increasing cooling rate. Based on the free growth model, a new numerical model considering the growth restriction effect of nanoparticles was established. The growth of grain was inhibited by the combining effect of solute and nanoparticles. The growth rate of grain is reduced due to part of the solid/liquid interface coated by nanoparticles. The blocking factor [Formula: see text] is linearly decreased with the coverage ratio [Formula: see text] which is proportional to the critical grain radius. The grain size decreases with increasing cooling rate and decreasing [Formula: see text] . This study is especially beneficial for Al alloys that have poisoning phenomenon inoculated by traditional refiner.