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In situ investigation of phase transformations in Ti-6Al-4V under additive manufacturing conditions combining laser melting and high-speed micro-X-ray diffraction.

ABSTRACT: We present combined in situ X-ray diffraction and high-speed imaging to monitor the phase evolution upon cyclic rapid laser heating and cooling mimicking the direct energy deposition of Ti-6Al-4V in real time. Additive manufacturing of the industrially relevant alloy Ti-6Al-4V is known to create a multitude of phases and microstructures depending on processing technology and parameters. Current setups are limited by an averaged measurement through the solid and liquid parts. In this work the combination of a micro-focused intense X-ray beam, a fast detector and unidirectional cooling provide the spatial and temporal resolution to separate contributions from solid and liquid phases in limited volumes. Upon rapid heating and cooling, the ?????' phase transformation is observed repeatedly. At room temperature, single phase ?' is observed. Secondary ?-formation upon formation of ?' is attributed to V partitioning to the ?-phase leading to temporary stabilization. Lattice strains in the ?'-phase are found to be sensitive to the ?'???? phase transformation. Based on lattice strain of the ?-phase, the martensite start temperature is estimated at 923?K in these experiments. Off-axis high speed imaging confirms a technically relevant solidification front velocity and cooling rate of 10.3?mm/s and 4500?K/s, respectively.

SUBMITTER: Kenel C

PROVIDER: S-EPMC5703903 | biostudies-other | 2017 Nov

REPOSITORIES: biostudies-other

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In situ investigation of phase transformations in Ti-6Al-4V under additive manufacturing conditions combining laser melting and high-speed micro-X-ray diffraction.

Kenel C C Grolimund D D Li X X Panepucci E E Samson V A VA Sanchez D Ferreira DF Sanchez D Ferreira DF Marone F F Leinenbach C C

Scientific reports 20171127 1

We present combined in situ X-ray diffraction and high-speed imaging to monitor the phase evolution upon cyclic rapid laser heating and cooling mimicking the direct energy deposition of Ti-6Al-4V in real time. Additive manufacturing of the industrially relevant alloy Ti-6Al-4V is known to create a multitude of phases and microstructures depending on processing technology and parameters. Current setups are limited by an averaged measurement through the solid and liquid parts. In this work the com ...[more]

PMID: 29180780

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Project description:Currently, selective laser melting (SLM) has been thriving in implant dentistry for on-demand fabricating dental implants. Based on the coarse microtopography of SLM titanium surfaces, constructing nanostructure to form the hierarchical micro-nano topography is effective in enhancing osseointegration. Given that current nanomodification techniques of SLM implants, such as anodization and hydrothermal treatment, are facing the inadequacy in costly specific apparatus and reagents, there has been no recognized nanomodified SLM dental implants. The present study aimed to construct hierarchical micro-nano topography on self-made SLM dental implants by a simple and safe inorganic chemical oxidation, and to evaluate its contribution on osteoblastic cells bioactivity and osseointegration. The surface chemical and physical parameters were characterized by FE-SEM, EDS, profilometer, AFM, and contact angle meter. The alteration on bioactivity of MG-63 human osteoblastic cells were detected by qRT-PCR. Then the osseointegration was assessed by implanting implants on the femur condyle of New Zealand Rabbits. The hierarchical micro-nano topography was constituted by the microrough surface of SLM implants and nanoneedles (diameter: 20∼50 nm, height: 150∼250 nm), after nanomodifying SLM implants in 30% hydrogen peroxide and 30% hydrochloride acid (volume ratio 1:2.5) at room temperature for 36 h. Low chemical impurities content and high hydrophilicity were observed in the nanomodified group. Cell experiments on the nanomodified group showed higher expression of mitophagy related gene (PINK1, PARKIN, LC3B, and LAMP1) at 5 days and higher expression of osteogenesis related gene (Runx2 and OCN) at 14 days. In the early stage of bone formation, the nanomodified SLM implants demonstrated higher bone-to-implant contact. Intriguingly, the initial bone-to-implant contact of nanomodified SLM implants consisted of more mineralized bone with less immature osteoid. After the cessation of bone formation, the bone-to-implant contact of nanomodified SLM implants was equal to untreated SLM implants and marketable TixOs implants. The overall findings indicated that the inorganic chemical oxidized hierarchical micro-nano topography could enhance the bioactivity of osteoblastic cells, and consequently promote the peri-implant bone formation and mineralization of SLM dental implants. This study sheds some light on improvements in additive manufactured dental implants.

Dataset Information

In situ investigation of phase transformations in Ti-6Al-4V under additive manufacturing conditions combining laser melting and high-speed micro-X-ray diffraction.

Publications

In situ investigation of phase transformations in Ti-6Al-4V under additive manufacturing conditions combining laser melting and high-speed micro-X-ray diffraction.

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