Purpose - The aim of the paper is the study of the change in the mechanical properties (and in particular in ductility), with the microstructure, of a biomedical Ti-6Al-4V alloy produced by different ...variants of selective laser melting (SLM).Design methodology approach - Ti-6Al-4V alloy produced by different variants of SLM has been mechanically characterized through tensile testing. Its microstructure has been investigated by optical observation after etching and by X-ray diffraction analysis.Findings - SLM applied to Ti-6Al-4V alloy produces a material with a martensitic microstructure. Some microcracks, due the effect of incomplete homologous wetting and residual stresses produced by the large solidification undercooling of the melt pool, are observable in the matrix. Owing to the microstructure, the tensile strength of the additive manufactured parts is higher than the strength of hot worked parts, whereas the ductility is lower. A pre-heating of the powder bed is effective in assisting remelting and reducing residual stresses, but ductility does not increase significantly, since the microstructure remains martensitic. A post-building heat treatment causes the transformation of the metastable martensite in a biphasic a-b matrix, with a morphology that depends on the heat treatment. This results in an increase in ductility and a reduction in strength values.Originality value - The study evidenced how it is possible to obtain a fully dense material and make the martensite transform in Ti-6Al-4V alloy through the variation of the SLM process. The stabilization of the microstructure also results in an improvement of the ductility.
Purpose - The purpose of this paper is the microstructural and mechanical characterization of a biomedical Ti-6Al-4V alloy produced by electron beam melting, and the study of the stability of the ...as-built microstructure upon heat treatment.Design methodology approach - Ti-6Al-4V alloy produced by electron beam melting has been mechanically characterized through tensile and fatigue testing. Its microstructure has been investigated by optical observation after etching and by X-ray diffractometry analysis. The stability of the microstructure of the as-built material has been deepened carrying out suitable heat treatments, after an analysis by dilatometry test.Findings - The microstructure of a Ti-6Al-4V alloy produced by electron beam melting has a very fine and acicular morphology, because of the intrinsically high-solidification rate of the process. This microstructure is very stable, and the traditional thermal treatments cannot modify it; the microstructure changes significantly only when an amount of strain is introduced in the material. However, the mechanical properties of the alloy produced by electron beam melting are good.Originality value - The paper provides evidence of the microstructural stability of the material produced by electron beam melting. Even if the microstructure of the as-built material is not recommended by the specific ISO standard, the related mechanical properties are fully satisfactory. This is a significant indication from the point of view of the production of Ti-6Al-4V orthopaedic and dental prostheses by electron beam melting.
It was the aim of this study to analyze osseointegrative properties of porous additive manufactured titanium implants made by direct metal laser sintering in a sheep model after an implantation ...period of 2 and 8 weeks.
Three different types of implants were placed in the pelvis of six sheep. In each sheep were placed three standard machined (M), three sandblasted and etched (SE), and three porous additive manufactured (AM) implants. Of these three implants (one per type) were examined histologically and six implants were tested biomechanically. Additionally a semiquantitative histomorphometrical and qualitative fluorescent microscopic analysis were performed.
After 2 and 8 weeks bone-to-implant-contact (BIC) values of the AM surface (2w: 20.49% ± 5.18%; 8w: 43.91% ± 9.69%) revealed no statistical significant differences in comparison to the M (2w: 20.33% ± 11.50%; 8w: 25.33% ± 4.61%) and SE (2w: 43.67 ± 12.22%; 8w: 53.33 ± 8.96%) surfaces. AM surface showed the highest increase of the BIC between the two observation time points. Considering the same implantation period histomorphometry and fluorescent labelling disclosed no significant differences in the bone surrounding the three implants groups. In contrast Removal-torque-test showed a significant improve in fixation strength (P ≤ 0.001) for the AM (1891.82 ± 308, 44 Nmm) surface after eight weeks in comparison to the M (198.93±88,04 Nmm) and SE (730.08 ± 151,89 Nmm) surfaces.
All three surfaces (M, SE, and AM) showed sound osseointegration. AM implants may offer a possible treatment option in clinics for patients with compromised bone situations.
Synthetic calcium phosphate bone substitutes are widely used in sinus graft procedures due to their osteoconductive and biocompatible properties. Hydroxyapatite (HA), beta-tricalcium phosphate ...(β-TCP), and HA/β-TCP composite are the most applied materials. The aim of this study was to propose a new mineralogical formulation, HA/tetracalcium phosphate (TTCP), as biomaterial for bone regeneration in the maxillary sinus.
Sinus grafts were performed by using granules of a HA/TTCP blend and a collagen membrane. Bone response at time points of 14 and 17 weeks was histologically evaluated.
After 14 weeks of healing, histomorphometric analysis showed the formation of new bone trabeculae among HA/TTCP granules. After 17 weeks, the bone trabeculae were thicker and HA/TTCP granules were still present. Histomorphometric analysis revealed a bone graft contact (BGC) of 64%.
After 17 weeks from implantation, HA/TTCP synthetic bone graft performed very well as osteoconductive material: BGC was found very high, and bone volume and vital bone showed an ideal bone density for implant placement. HA/TTCP granules are accounted for to accelerate new bone formation and to reduce the time needed for the graft healing, thus achieving high quantity of the new bone formed.
Purpose The purpose of this paper is the microstructural and mechanical characterization of a biomedical Ti6Al4V alloy produced by electron beam melting, and the study of the stability of the asbuilt ...microstructure upon heat treatment. Designmethodologyapproach Ti6Al4V alloy produced by electron beam melting has been mechanically characterized through tensile and fatigue testing. Its microstructure has been investigated by optical observation after etching and by Xray diffractometry analysis. The stability of the microstructure of the asbuilt material has been deepened carrying out suitable heat treatments, after an analysis by dilatometry test. Findings The microstructure of a Ti6Al4V alloy produced by electron beam melting has a very fine and acicular morphology, because of the intrinsically highsolidification rate of the process. This microstructure is very stable, and the traditional thermal treatments cannot modify it the microstructure changes significantly only when an amount of strain is introduced in the material. However, the mechanical properties of the alloy produced by electron beam melting are good. Originalityvalue The paper provides evidence of the microstructural stability of the material produced by electron beam melting. Even if the microstructure of the asbuilt material is not recommended by the specific ISO standard, the related mechanical properties are fully satisfactory. This is a significant indication from the point of view of the production of Ti6Al4V orthopaedic and dental prostheses by electron beam melting.
Purpose The aim of the paper is the study of the change in the mechanical properties and in particular in ductility, with the microstructure, of a biomedical Ti6Al4V alloy produced by different ...variants of selective laser melting SLM. Designmethodologyapproach Ti6Al4V alloy produced by different variants of SLM has been mechanically characterized through tensile testing. Its microstructure has been investigated by optical observation after etching and by Xray diffraction analysis. Findings SLM applied to Ti6Al4V alloy produces a material with a martensitic microstructure. Some microcracks, due the effect of incomplete homologous wetting and residual stresses produced by the large solidification undercooling of the melt pool, are observable in the matrix. Owing to the microstructure, the tensile strength of the additive manufactured parts is higher than the strength of hot worked parts, whereas the ductility is lower. A preheating of the powder bed is effective in assisting remelting and reducing residual stresses, but ductility does not increase significantly, since the microstructure remains martensitic. A postbuilding heat treatment causes the transformation of the metastable martensite in a biphasic ab matrix, with a morphology that depends on the heat treatment. This results in an increase in ductility and a reduction in strength values. Originalityvalue The study evidenced how it is possible to obtain a fully dense material and make the martensite transform in Ti6Al4V alloy through the variation of the SLM process. The stabilization of the microstructure also results in an improvement of the ductility.
