Ni-Ti Alloys Prepared by Reactive Sintering and Spark Plasma Sintering Method

Abstract

Powder metallurgy processes such as reactive sintering and spark plasma sintering are simple methods for synthesis of Ni-Ti shape memory alloys. These methods enable one to prepare alloys with exact chemical composition, while there is no danger of alloy contamination by the material of crucible which occurs with vacuum induction melting. The main reaction of the formation of NiTi phase starts approx. at 970 °C, while this temperature depends on the chemical composition of powder mixture and the heating rate used. The transformation temperatures are influenced by addition of alloying elements. The spark plasma sintering method produces a highly dense material but the combination of milling and spark plasma sintering suppresses shape memory effects and undesirable phases are formed.