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Kanwal Chadha,Yuan Tian,John Spray,Clodualdo Aranas 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.1
Microtextural characterization using electron backscatter difraction analysis was performed on laser powder bed fusion manufactured SS316L (SS316L). The crystallographic textures of as-printed (AP) and hot isostatic pressed (HIP) samples havebeen determined using orientation distribution function maps. The AP sample consists of mostly<110>||BD and<100>||BDfber textures without any clear presence of twins. Conversely, the HIP sample featured<110>||BD and<111>||BD grains. The formation of<111>||BD texture was due to the deformation associated with the HIP process. Moreover, HIP generateda signifcant fraction of coincident site lattice Σ3 boundaries due to the low stacking fault energy of SS316L. These twinboundaries allow considerable plasticity during subsequent deformation. The spacing of deformation twins is wider (1–5 μm)compared to the subgrain boundaries (0.2–0.7 μm). Kernel Average Misorientation maps depict the occurrence of dynamicrecrystallization, which is assisted by deformation twinning. The results explain the increased ductility of LPBF-produced,HIP processed SS316L without sacrifce to its tensile strength.
Nelson Luis Costa dos Santos Filho,Eden Santos Silva,Clodualdo Aranas Jr.,Fulvio Siciliano,Gedeon Silva Reis,Samuel Filgueiras Rodrigues 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11
The correlation between hardening and softening in an ASTM F-1586 stainless steel used as biomaterial was investigatedby means of hot torsion simulations. Multi-pass deformation under continuous cooling was employed to simulate industrialhot rolling. Samples were subjected to 17 deformation passes of strains of 0.20 and 0.30, strain rate of 1.0 s−1 in a temperaturerange of 1250 to 930 °C. Interpass times (tp) of 5.0, 10, 20, 40, and 80 s were used. The obtained results showed directdependence of the mean flow stress (MFS) and all applied thermomechanical parameters. The work hardening rate associatedwith the degree of stress accumulation (Δσ) inhibited the metadynamic recrystallization. This led to the variation ofthe non-recrystallization temperature (Tnr), associated with intense static recovery in the material. From the experimentaldata, a constitutive function of the mean flow stress (MFS) obtained through multiple nonlinear regression technique wasproposed. The study aimed to have a better understanding of the physical metallurgy behind the thermomechanical behaviorof the steel under a multi-pass process. The results allowed to monitor the recrystallized fraction (X) and the grain size (d)during the simulated conditions.
Kim, Sang Hoon,Yeon, Si-Mo,Kim, Jin Hak,Park, Seong Je,Lee, Ji Eun,Park, Suk-Hee,Choi, Joon-Phil,Aranas, Clodualdo,Son, Yong American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.18
<P>A novel In-Sn-Bi solder with a low electrical resistivity of 14.3 × 10<SUP>-6</SUP> Ω cm and a melting temperature of 99.3 °C was produced for use in adhesive joining on a flexible poly(ethylene terephthalate) substrate. We determined that the fine microstructure of the In-based solder (which had an average phase size of 62.2 nm) strongly influenced its superplasticity and toughness at diffusive temperatures of 55-85 °C because the late-forming BiIn intermetallic compound (IMC) suppressed the growth of two other IMCs, In<SUB>3</SUB>Sn and In<SUB>0.2</SUB>Sn<SUB>0.8</SUB>, which formed earlier in the soldering process. Thus, an elongation of 858.3% and toughness of 36.0 MPa were obtained at a temperature of 85 °C and a strain rate of 0.0020 s<SUP>-1</SUP>. However, due to phase boundary fracturing, the phase-refined solder exhibited a slightly more brittle nature (with an elongation of 74.3%) at room temperature compared with a standard In-Sn solder consisting only of the In<SUB>3</SUB>Sn and In<SUB>0.2</SUB>Sn<SUB>0.8</SUB> IMCs, which had a slightly larger phase size of 84.9 nm and higher ductility (with an elongation of 80.7%). In terms of superplastic deformation, the conventional fracture system based on the Hall-Petch effect transformed into phase boundary sliding at the solder operating temperature, significantly enhancing ductility.</P> [FIG OMISSION]</BR>