Spark Plasma Sintering, Microstructures, and Mechanical Properties of Macroporous Titanium Foams

Abstract

Porous materials with interconnected porosity have widespread applications in many fields of engineering. [1] Bulk porous metallic materials (honeycomb, foam, and hollow spheres) are known for their interesting combinations of the advantages of a metal (strong, hard, tough, electrically, and thermally conductive, etc.) with the functional properties of porous structures (lightweight with adjustable properties by selecting the density. [2] Because of this, porous metals are interesting for a number of engineering applications such as structural panels, energy absorption devices, acoustic damping panels, compact heat exchangers, and biomedical implants etc. [3] Porous titanium (Ti) and its alloy were widely used in the biomedical field due to their outstanding mechanical properties, low density, chemical resistance, and biocompatibility. As a kind of long-term load-bearing implant, the porous structures of Ti and its alloy could lead to a reliable anchoring of host tissue into the porous structure, and allow mechanical interlocking between bone and implant. [4] The ingrowths of bone into the porous structure could ensure a good transfer of mechanical forces. Therefore, a porous structure is preferable for the Ti and its alloys using as bone scaffolds.However, porous Ti and its alloys are difficult to be produced from the liquid state, due to the high melting point, the high reactivity at high temperature above 1000 8C and the contamination susceptibility. Thus, fabrication processes for porous Ti has to date focused on the powder metallurgy (PM) route and avoided the liquid route. [5] Many techniques have been applied to produce porous Ti and its alloy implants in recent years. [6][7][8][9][10] Nevertheless, there are still problems to be solved in the field of porous Ti for biomedical applications [11] : the difficulty to create controlled porosity and pore sizes, the insufficient knowledge of porous structureproperty relationships, the requirements of new sintering techniques with rapid energy transfer, and less energy consumption and so on.Spark plasma sintering (SPS) as one of the field assisted sintering techniques, is a relative new sintering technique for PM and ceramics. SPS is a high efficient and energy saving powder consolidation and sintering technology capable of processing conductive and non-conductive materials. [12] However, most of SPS researches were performed on dense materials; fewer studies were on porous materials. [13] The SPS studies on porous Ti alloys were mainly using low temperature and low pressure to decrease the relative density of samples. [14][15][16][17][18][19] The samples exhibited pore sizes of some tens of micrometers and a porosity in the range of 20-45%. As bone foams, high porosity (>50%) and macropore size (>200 mm) are essential requirements for the bone growth and the osteoconduction. [20,21] Macroporous nanostructured tricalcium phosphate scaffolds have been successfully COMMUNICATION [*] Dr. for his support in mechanical testing.Macroporous pure titanium (Ti) foams with...

Sintering and Heat Treatment of Titanium Alloys by Pulsed Electric Current Sintering

“…In this study, the Ti6Al4V foams were fabricated by using PECS at controlled porosity followed by dissolution of NaCl phase and post heat treatment at 1100 o C. Previous investigations showed that high-density pure Ti foams can be fabricated with NaCl as spacer by the PECS at 700 o C for 8 min under 50 MPa [11]. However, the Ti6Al4V/NaCl mixture cannot be densified at the same condition.…”

“…Thus the local surfaces of the particles melt, allowing junctions to be formed between particles in contact. The combination of the PECS technique with a NaCl space holder was used in porous pure Ti to fabricate macroporous Ti foams with controlled architectures recently [11]. This indicated that the PECS may be able to fabricate Ti6Al4V foams from the Ti6Al4V/NaCl powder mixture.…”

Metallic materials for medical use

“…Some of the most recently used are partial (loose) sintering of metal powders [28], space holder method [20], spark plasma sintering (porous Ti with yield strength 27.2-94.2 MPa and elastic modulus 6.2-36.1 GPa was derived in [29]), microwave sintering (Ti-6Al-4V/multiwall carbon nanotubes composite with porosity of approximately 25%, yield strength of 145.48 ± 27.28 MPa and elastic modulus of 10.87 ± 2.46 GPa obtained in [30]), combustion synthesis [31], selective laser melting (porous Ti-10Mo alloy with compressive yield strength of 95.59 MPa and an elastic modulus of 4.89 GPa was created in [23]). "3D printing" techniques seems to be most promising among them, since they allow the formation of desired porous structure along with exact implant shape according to the CAD model based on tomography data.…”

Near-Net Shapes Al2O3–SiCw Ceramic Nanocomposites Produced by Hybrid Spark Plasma Sintering

“…The main advantage of the spark plasma sintering technique is very high heating and cooling rates that allow to produce highly dense traditionally difficult-to-sinter materials. A wide range of material types such as nanostructured materials [2], functional-graded materials [3], hard alloys [4], titanium alloys [5], bioceramics [6], porous materials [7] for various applications was fabricated by spark plasma sintering.…”