Abstract
Commercially pure (c.p.) titanium grade IV with a bimodal microstructure is a promising material for biomedical implants. The influence of the processing parameters on the physical, microstructural, and mechanical properties was investigated. The bimodal microstructure was achieved from the blends of powder particles with different sizes, while the porous structure was obtained using the space-holder technique (50 vol.% of ammonium bicarbonate). Mechanically milled powders (10 and 20 h) were mixed in 50 wt.% or 75 wt.% with c.p. titanium. Four different mixtures of powders were precompacted via uniaxial cold pressing at 400 MPa. Then, the specimens were sintered at 750 °C via hot pressing in an argon gas atmosphere. The presence of a bimodal microstructure, comprised of small-grain regions separated by coarse-grain ones, was confirmed by optical and scanning electron microscopies. The samples with a bimodal microstructure exhibited an increase in the porosity compared with the commercially available pure Ti. In addition, the hardness was increased while the Young’s modulus was decreased in the specimens with 75 wt.% of the milled powders (20 h).
Highlights
The research field related to biomedical materials has been grown in recent decades as a result of the demand for implants for bone replacement [1]
The Scanning Electron Microscopy (SEM) images of the as-received titanium powders are shown in the Figure 1a, where an irregular shape is appreciated, typically from its processing via hydrogenation/dehydrogenation
Some investigations have shown the relevance of spacer particle size and morphology to generate a structure where the total porosity is controlled in an appropriate manner [17,36,59]
Summary
The research field related to biomedical materials has been grown in recent decades as a result of the demand for implants for bone replacement [1]. There is mismatch between the stiffness of bone and metallic biomaterials. This incompatibility generates the stressshielding phenomenon which promotes bone resorption at the implant–bone interface and can even induce implant failure [4,5]. It is well known that porous structures exhibit lower elastic modulus than their fully-dense counterparts [3,6]. It has been identified that titanium components that possess optimal macro/micro porosities allow for the tuning of the elastic modulus in a considerably wide range, which favors bone cell ingrowth and vascularization [3]
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