Intermetallic phase formation during combustion synthesis of mechanically activated Ni-Ti alloy

Subject Areas : Mechanical Engineering

Seyed Khatiboleslam  Sadrnezhaad ¹ (Sharif University of Technology)
Shahin  Katiraei ² ()
Abbas  Ghasemi ³ ()

Received: 2014-07-19 Accepted : 2017-10-31 Published : 2014-12-01

Keywords:

Abstract :

Intermetallic phase formation and oxidation reaction during combustion synthesis (CS) of Ni-Ti equiatomic mixture are affected by mechanical activation (MA) and pre-heating conditions. Important parameters are ignition time, reaction duration, temperature rise, microstructural change, titanium oxidation and intermetallic phase formation. Superelasticity and shape memory effects are influenced by two-stage austenite-rhombohedral and rhombohedral-martensite transformations detected by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) of the combusted samples. Tension tests indicated superelastic behavior after 1 h, production of Ni3Ti after ½ h and delayed superelastic/thermoelastic behavior after 2 h MA. Results indicate that pre-combustion heating fosters mono-phase formation and titanium oxidation; while mechanical activation lowers ignition-start-time, synthesis-duration and Ni3Ti formation.