[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

SKPFM measured Volta potential correlated with strain localisation in microstructure to understand corrosion susceptibility of cold-rolled grade 2205 duplex stainless steel

With the increasing application of orthopedic scaffolds, a dramatically increasing number of requirements for scaffolds are precise The porous structure has been a fundamental design in the bone tissue engineering or orthopedic clinics because of its low Young's modulus, high compressive strength, and abundant cell accommodation space The porous structure manufactured by additive manufacturing (AM) technology has controllable pore size, pore shape, and porosity The single unit can be designed and arrayed with AM, which brings controllable pore characteristics and mechanical properties This paper presents the current status of porous designs in AM technology The porous structures are stated from the cellular structure and the whole structure In the aspect of the cellular structure, non-parametric design and parametric design are discussed here according to whether the algorithm generates the structure or not The non-parametric design comprises the diamond, the body-centered cubic, and the polyhedral structure, etc The Voronoi, the Triply Periodic Minimal Surface, and other parametric designs are mainly discussed in parametric design In the discussion of cellular structures, we emphasize the design, and the resulting biomechanical and biological effects caused by designs In the aspect of the whole structure, the recent experimental researches are reviewed on uniform design, layered gradient design, and layered gradient design based on topological optimization, etc These parts are summarized because of the development of technology and the demand for mechanics or bone growth Finally, the challenges faced by the porous designs and prospects of porous structure in orthopedics are proposed in this paper

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Porous Scaffold Design for Additive Manufacturing in Orthopedics: A Review.

Titanium alloys have been considered as unique materials for many years. Even their microstructure and operational properties have been well known and described in details, the new technologies introduced—e.g., 3D printing—have restored the need for further research in this area. It is understood that martensitic transformation is usually applied in heat treatment of hardenable alloys (e.g., Fe alloys), but in the case of titanium alloys, it also occurs during the thermomechanical processing or advanced additive manufacturing. The paper summarizes previous knowledge on martensite formation and decomposition processes in two-phase titanium alloys. It emphasizes their important role in microstructure development during conventional and modern industrial processing.

https://www.mdpi.com/2075-4701/11/3/481/pdf

Martensite Formation and Decomposition during Traditional and AM Processing of Two-Phase Titanium Alloys—An Overview

In many processing operations, it is critical to know the relationship between the resultant sample geometry and the distribution of crystallographic or grain orientations within the polycrystalline aggregates. The spatial variations in crystallographic texture associated with different parts of the sample geometry can influence differences in the plastic response within different regions of a sample. In this paper we present a study of such local variations in the texture (microtexture) as well as grain boundary or mesotexture associated with copper wire and its implications for micromechanical inhomogeneity within a sample volume. The unique experimental and analytical aspects of such microtexture characterization are discussed along with the issues of grain boundary structural parameters and its role in microtexture and anisotropy. The presence of differences in twin frequency in different regions of the sample is suggested as a possible source of strength anisotropy.

Microtexture and anisotropy in wire drawn copper

The research demonstrates microstructural changes and development of specific texture in Ti-6Al-4V specimens produced by electron beam melting (EBM) under different conditions. The effect of two factors, namely, raw material (powder) recycling and hot isostatic pressing (HIP), on the EBM produced samples structure and properties, has been explored. The as-printed and treated samples were investigated using electron backscattered diffraction (EBSD) analysis. Modification of mechanical properties after the EBM and HIP are explained by the EBSD data on microstructural phenomena and phase transformations. The work is devoted to assessing the possibility of reusing the residual titanium alloy powder for the manufacture of titanium components by the combination of EBM and HIP methods.

https://www.mdpi.com/1996-1944/14/16/4473/pdf

Texturing and Phase Evolution in Ti-6Al-4V: Effect of Electron Beam Melting Process, Powder Re-Using, and HIP Treatment

X-ray diffraction analysis and transmission and scanning electron microscopy have been used to study regularities of the formation of structure and phase composition of a VT16 alloy during its quenching. The formation of an athermal ω phase in the VT16 alloy with the initial (α + β) structure during quenching of the alloy from 800°C was found to be possible. Quenching temperatures (Tq) at which various metastable phase compositions, such as the metastable β solid solution, β + α″ + ω, β + α″, and α″ martensite, are formed have been determined to be 750, 800, 750–850, and ≤850°C, respectively. Dependences of variations in the volume fractions of phases were plotted. It has been shown that, at quenching temperatures close to the β-transus, the active growth of β-phase grains takes place at the expense of a decrease in the α-phase volume fraction.

Effect of quenching temperature on structure and properties of titanium alloy: Structure and phase composition

Regularities of the formation of physicomechanical properties of the VT16 alloy (Ti-3.33Al-5.18Mo-4.57V, wt %) quenched after furnace and rapid heating have been established using optical microscopy, X-ray diffraction (XRD), and dynamic mechanical analysis. It has been shown that changes in the modulus of elasticity of the VT16 alloy correlate with a decrease in the volume fraction of the α phase in the structure, except for a slight increase in the modulus of elasticity (related to the presence of the ω phase) in the case when quenching temperatures of 800–825°C were used. It has been found that the use of rapid heating to the quenching temperature leads to an increase in the temperature of the alloy transition into the single-phase β state, hampers grain growth during heating for quenching at temperatures close to the polymorphic-transition temperature, and creates conditions for more efficient strengthening in the course of subsequent aging.

Effect of quenching temperature on structure and properties of titanium alloy: Physicomechanical properties

The texture of the cold-drawn copper wire was investigated along the radius using electron backscatter diffraction. The complex fiber texture of the central region of the wire was considered as the rolling texture consisting of a set of preferred orientations. The texture of the periphery region was revealed to be similar to the shear texture. The orientation-dependent properties of the wire were proven to be determined by the texture of the near-surface layers.

Fiber vs Rolling Texture: Stress State Dependence for Cold-Drawn Wire

Methods of X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and differential scanning calorimetry have been used to study the formation of the structure and phase composition upon the cold rolling of rodlike semi-finished products of the VT16 alloy quenched for martensite (Tq = Tpt − 10 K). It has been established that, with an increasing degree of elongation caused by rolling in the range under investigation, a more complete deformation-induced transformation occurs according to the scheme α″ → (α′ + βa) with the formation of a βa solid solution with an anomalously large lattice parameter because of the development of accommodation processes due to the difference in the specific volumes of the initial (α″) and arising (α′) martensitic phases. A correlation between the phase composition and the microhardness and elastic characteristics has been established. The temperature intervals of the occurrence of the processes of solid-solution decomposition have been determined upon the continuous heating in the quenched and cold-rolled states.

S. I. Stepanov

Papers

Texturing and Phase Evolution in Ti-6Al-4V: Effect of Electron Beam Melting Process, Powder Re-Using, and HIP Treatment

Effect of quenching temperature on structure and properties of titanium alloy: Structure and phase composition

Effect of quenching temperature on structure and properties of titanium alloy: Physicomechanical properties

Fiber vs Rolling Texture: Stress State Dependence for Cold-Drawn Wire

Structural and phase transformations in a quenched two-phase titanium alloy upon cold deformation and subsequent annealing