Brittle precipitates regulation in Ni/Ti composition gradient materials under pulsed current

There are mass brittle precipitates in Ni/Ti bimetals, which seriously weaken the metallurgical bonding strength. The gradient structure can reduce the formation rate of brittle precipitates, but cannot avoid them. In this paper, the pulsed current was used to regulate the brittle precipitates in Ti6Al4V/Inconel 625 gradient materials, and the effect is remarkable. The pulsed current can promote the dissolution of main precipitates including Laves, (Cr, Mo), Ni 3 Ti, NiTi, NiTi 2 and α -Ti, resulting in better structural homogenization and stability. Meanwhile, the recrystallization was also accelerated during pulsed treatment to release the stress concentration. Furthermore, the pulsed current also plays a significant role in pushing the evolution of snowflake-like particles to the spherical shape. Finally, the compression and hardness tests showed that the mechanical properties of Ni/Ti gradient materials can be significantly improved after pulsed treatment.