다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

https://spiral.imperial.ac.uk/bitstream/10044/1/67871/2/J291_Leung_Acta_as_accepted_181212.pdf

The effect of powder oxidation on defect formation in laser additive manufacturing

An overview of tailoring strain delocalization for strength-ductility synergy

Lightweight materials are of paramount importance to reduce energy consumption and emissions in today's society. For materials to qualify for widespread use in lightweight structural assembly, they must be weldable or joinable, which has been a long-standing issue for high strength aluminum alloys, such as 7075 (AA7075) due to their hot crack susceptibility during fusion welding. Here, we show that AA7075 can be safely arc welded without hot cracks by introducing nanoparticle-enabled phase control during welding. Joints welded with an AA7075 filler rod containing TiC nanoparticles not only exhibit fine globular grains and a modified secondary phase, both which intrinsically eliminate the materials hot crack susceptibility, but moreover show exceptional tensile strength in both as-welded and post-weld heat-treated conditions. This rather simple twist to the filler material of a fusion weld could be generally applied to a wide range of hot crack susceptible materials.

/pdf/nanoparticle-enabled-phase-control-for-arc-welding-of-4fgm69e8sr.pdf

Nanoparticle-enabled phase control for arc welding of unweldable aluminum alloy 7075.

The selective laser melting (SLM) technology is widely used for the manufacturing of Ti6Al4V alloy components in the biomedical and aerospace industries, and the residual pores are one of the significant defects obstructing its further application. X-ray computed tomography (XCT) technique was applied for the examination and analysis of the spatial and morphological features of pore defects, which will influence the tensile properties of the SLM-manufactured Ti6Al4V samples. Hence, the effects of processing parameters on pore defects and their formation mechanism are discussed thoroughly. The results showed that two major types of pore defects are observed: the lack-of-fusion caused by low volumetric energy density (VED), and the keyhole mode resulting from excessive energy densities. The highest relative density of 99.995% was obtained at a VED value of 58.8 J/mm3. Besides, the quantitative information of the porosity defects, such as size distribution, morphology and formation direction, was evaluated using XCT to reveal their formation mechanisms. Furthermore, the tensile properties of SLM-manufactured Ti6Al4V alloy under different VED values were evaluated to correlate with the porosity variation. Overall, the tensile strength and ductility were notably degraded with the increase of porosity. The fractography study based on XCT and SEM showed that lack-of-fusion and porosities are responsible for the early fracture. In conclusion, the XCT technique can provide direct and precise inspection of the process of laser-based additive manufacturing to control the overall quality.

Study of pore defect and mechanical properties in selective laser melted Ti6Al4V alloy based on X-ray computed tomography

https://macsphere.mcmaster.ca/bitstream/11375/23809/1/2016_ActaMat_Biao.pdf

Dendritic evolution during coarsening of Mg-Zn alloys via 4D synchrotron tomography

The influence of nanoparticles on dendritic grain growth in Mg alloys

Fast synchrotron X-ray tomographic quantification of dendrite evolution during the solidification of Mg-Sn alloys

https://macsphere.mcmaster.ca/bitstream/11375/24382/1/2018_ActaMat_Shuai_etal.pdf

Sansan Shuai

Papers

Study of pore defect and mechanical properties in selective laser melted Ti6Al4V alloy based on X-ray computed tomography

Dendritic evolution during coarsening of Mg-Zn alloys via 4D synchrotron tomography

The influence of nanoparticles on dendritic grain growth in Mg alloys

Fast synchrotron X-ray tomographic quantification of dendrite evolution during the solidification of Mg-Sn alloys

Synchrotron tomographic quantification of the influence of Zn concentration on dendritic growth in Mg-Zn alloys