TiNi-Based Shape Memory Foams Produced by Self-Propagating High Temperature Synthesis
TiNi-Based Shape Memory Foams Produced by Self-Propagating High Temperature Synthesis
Thursday, May 23, 2013: 15:15
Congress Hall 2 (OREA Pryamida Hotel)
The crystalline structure, martensitic transformations and shape memory effects were studied in the TiNi-based shape memory foams. The TiNi foams of different compositions were produced by self-propagating high temperature synthesis (SHS) at different pre-heating temperatures. It was shown that a pre-heating temperature hardly influenced the properties of TiNi-based foams. The main parameter influencing the structure and properties of TiNi-based foams was Ni concentration in the Ti+Ni powder mixture using for SHS. It was found that an increase in the Ni concentration from 45 to 52 at % resulted in a decrease in volume fractions of precipitates (Ti2Ni, Ti3Ni4, TiNi3) and an increase in volume fraction of TiNi phase. However, as concentration of Ni in TiNi phase increased, volume fraction of TiNi phase undergoing a martensitic transformation decreased. In this case TiNi-based foams demonstrated poor functional properties. To improve a martensitic transformation kinetics and shape memory effects TiNi-based foams were subjected to annealing at a temperature range of 300 – 600 oC for duration of 30 – 240 min. It was found that maximum of volume fraction of TiNi phase undergoing a martensitic transformation was observed in TiNi-based foams annealed at 500 oC for 2 hours. It resulted in observation of good shape memory and pseudoeleasticity effects. It was shown that Ti55Ni45 foam demonstrated functional properties like a Ti50Ni50 cast alloy and properties of Ti50Ni50 and Ti48Ni52 foams were closed to the properties of Ti49.3Ni50.7 cast alloy. It was shown that variation in Ni concentration and annealing parameters allowed one to obtain a TiNi foams with a different temperatures of martensitic transformations and various functional properties which will be used for different applications.