On preparation of bimodal Ti-5Al-5V-5Mo-3Cr-0.4Si (Ti-5553s) alloy: α+β forging and heat treatment

The role of the forging temperature, forging strain and solution temperature on the preparation of bimodal Ti-5553s alloy has been studied in this paper. The initial full lamellar Ti-5553s alloy could be forged within a wide temperature scope of 600-800 °C by a high compression strain (0.88), demonstrating the excellent thermal processing ability in the α+β field. The sub-transus forging is essential to the preparation of the bimodal alloy, and the recommended forging temperature and the critical forging strain for the lamellar Ti-5553 alloy are 780 °C and 0.3, respectively. To prevent the coarsening of the β grain, the recommended solution temperature for bimodal alloy lies in 790-820 °C. The decrease in the forging temperature or the increase in the solution temperature may lead to the increase in the Vickers hardness of the bimodal alloy. The relationship between the forging factors, the microstructure and the mechanical performance of Ti-5553s alloy has been developed, and these laboratory results provide a guideline for the preparation of the large-scale Ti-5553s alloy component with the homogeneous bimodal microstructure.