Preparation And Characterization Of Porous NiTi Alloys

Porous NiTi alloy was prepared using elemental powder sintering method, which have excellent compatibility of biologic mechanics for the porous microstructure. The porous NiTi alloy can keep the growth of bionic tissue and the transmission of body fluid, so that the implant and bone tissue of the body combined very solid. So the porous NiTi alloy will replace hard tissue and surgical implant material in the future. The power of NiTi alloy prepared by milling and the effection of milling time was investigated in power size, morphology and distribution. At the same time, the preparation parameters such as sintering temperature, sintering time, pre-forming pressure were studied for the infection of porosity, morphology, phase composition and so on. The dissolution behavior of Ni was studied in Hank's by using UV photometer.The result indicated that preparation of the NiTi alloy powder in the size distribution of 1.986～55.84um. With the milling time, the powder particle size increased and then decreased after the thinning, surface roughness decreased after the first increase.In a variety of prepared sintering conditions, porous NiTi alloys with the main component for the B2 (NiTi) phase, B19 (NiTi) and with Ni₄Ti₃ phase, in which the main phase with B2. To a certain temperature range, with the sintering temperature, porous NiTi alloys, the average pore size increased gradually, toward uniform pore distribution, gradually smooth-walled hole, with the extension of the holding time, the pore size decreases, the liquefaction phenomenon obviously. At the same time as the sintering temperature and holding time to increase the porous NiTi alloys in the name of increased compressive strength, but the holding time is too long, porous NiTi alloys porosity will be reduced. With the pre-forming pressure increases, porous NiTi alloys reduce the porosity, the name of increasing compressive strength. However, pre-forming pressure not be too big, blank or pre-stress is too large, easy to make the process of sintering samples have cracks. With the added pore volume of porous NiTi alloys in the name of the gradual lowering of compressive strength.Heat treatment process of porous NiTi alloys pore morphology, phase composition and mechanical properties, such as the impact of research results show that: after the heat treatment of porous NiTi alloy block away most of the skeleton on the porous, phase composition has not changed, but the number of Ni₄Ti₃ phase, in the name compressive strength increased slightly.Ni ion dissolution behavior study: porous NiTi alloy immersed in Hank's solution, with the increase in the soaking time, Ni-ion dissolution rate of decline in the latter part of the immersion, the dissolution rate steady,and relatively low.