A. Coda, L. Fumagalli, M. Bertoldi, SAES Getters S.p.A, Lainate, Italy
Porous NiTi shape memory alloy are an active area of research for medical application due to their similar structure and to their good biointegration into human bone. Powder metallurgy is a promising method for the production of near-net-shape components of NiTi alloys. In this work, NiTi pre-alloyed powders were used for the preparation of sintered porous sheets with sound functional properties. A preliminary chemical and physical characterization of NiTi powders was done by using common analytical techniques. A better understanding of the microstructural and functional properties and the effects of different annealing treatments on NiTi powders will be presented.
Preparation of NiTi porous sheets from the characterized powders was conducted by sintering. The powder characterization was a necessary starting point to set up the sintering experiments. Chemical and microstructural properties of the sintered samples were investigated by chemical analysis, scanning electron microscopy (SEM) and differential calorimetry (DSC). Effects of composition, sintering parameters and aging treatments on shape memory and superelastic behavior were investigated by dynamo-mechanical analysis (DMA).
The summary of data suggests that the evolution of DSC charts of NiTi sintered porous sheets may be very complex, depending on several factors, such as starting composition, impurity content, grain size distribution, homogeneity of the pre-alloyed powders. DMA results confirm the feasibility of NiTi porous parts by sintering processes.
Summary: The microstructure characterization on pre-alloyed Nitinol powder and the dynamo-mechanical behaviour of sintered sheets is presented.
