Influence of the recrystallization process on the mechanical properties of Ti₅₁Ni₁₃Pd₃₆ high temperature memory alloy

The Ingots of high temperature shape memory alloy Ti₅₁Ni₁₃Pd₃₆ were prepared by means of levitation melting technology in a high frequency vacuum furnace. The samples were subjected to a cold working and a sequent annealing treatment to provide improvement in its mechanical properties and the shape memory effect. It was found that recovery of the cold-worked alloys took place near 673 K and the recrystallization temperature was approximately 748 K. The average grain size decreased with the increase of annealing temperature below 923 K, then increased for temperatures above 923 K. The smallest average grain size of about 3.5 μm, being approximately 10 times smaller than the hot rolled one, revealed the best combination of mechanical properties for the alloy, which was annealed at 923 K for 1 hour. The resulting change of forward and reverse transformation temperatures shows that both curves of A_p and M_p temperatures display a maximum appearing near 873 K annealing temperature, where the smallest grain size was obtained.