Akiyoshi Araki - Academia.edu (original) (raw)

Papers by Akiyoshi Araki

The Japan Society of Applied Physics, Feb 8, 2016

Springer eBooks, 2015

The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni2Si precipitates have been... more The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni2Si precipitates have been studied. The SEM/EBSP result indicated that the nano-scale deformation twins cannot grow to micro twins during room temperature deformation. The results also revealed that the formation and growth of deformation twinning needs certain strain and stress level in the alloy aged at 723 K for 3.6k and deformed at 77 K. In contrast, it started from initial stage of deformation in the alloy aged at 723 K for 64.8 ks and deformed at 77 K. These results indicate that the deformation twinning needs certain level of stress rather than strain in precipitate strengthened Cu-Ni-Si alloy.

Materials transactions, 2016

Micro-tensile tests of pure copper and a precipitation strengthening-type Cu alloy, Cu-Ni-Si allo... more Micro-tensile tests of pure copper and a precipitation strengthening-type Cu alloy, Cu-Ni-Si alloy, were performed using micro-sized tensile specimens with 10 × 10 µm 2 in cross-section and 40 µm in length and a micro-gripper, which were fabricated by a focused ion beam system. The obtained experimental results were compared with the results of Cu-Ni-Si alloy bulk sample. The micro-tensile tests of both pure Cu and Cu-Ni-Si alloy showed the typical serrations caused by moving of dislocations and a decrease of ow stress by the necking. In the Cu-Ni-Si alloy, characteristic deformation of work-hardening was observed. Electron back scatter diffraction analysis showed a gradual change in crystal orientation at the necking area.

Crystals, Dec 21, 2020

The aim of this study is to investigate a characteristic deformation behavior of a precipitation ... more The aim of this study is to investigate a characteristic deformation behavior of a precipitation strengthening-type Cu-Ni-Si alloy (Cu-2.4Ni-0.51Si-9.3Zn-0.15Sn-0.13Mg) by microcompression specimens. Three micropillars with a square cross-section of 20 × 20 × 40 µm 3 were fabricated by focused ion beam (FIB) micromachining apparatus and tested by a machine specially designed for microsized specimens. The three pillars were deformed complicatedly and showed different yield strengths depending on the crystal orientation. The micromechanical tests revealed work hardening by the precipitation clearly. Electron backscattered diffraction analysis of a deformed specimen showed a gradual rotation of grain axis at the grain boundaries after the compression test.

The Japan Society of Applied Physics, 2016

Cu materials are often used as micro-components in MEMS devices [1]. For applications of material... more Cu materials are often used as micro-components in MEMS devices [1]. For applications of materials in MEMS, investigating mechanical properties of micro-sized specimens is very important. Mechanical behaviors of samples with small dimensions are different from that of bulk materials, which is known that strength of the specimen is stronger when the specimen size is decreased. So, micro-mechanical test has been extensively studied since when a technique was proposed and developed by Uchic et al [2]. Based on this technical background, we have reported several studies on micro-bending [3], micro-compression [4] and micro-tensile [5] tests with a specially designed micro-testing machine. Cu-Ni-Si alloy is a precipitation strengthening-type alloy and receives a lot of attention for its high strength, high electrical conductivity and excellent bending workability [5]. However, there is still no report on micro-mechanical properties of the alloy. In this study, we report deformation behav...

Crystals, 2020

The aim of this study is to investigate a characteristic deformation behavior of a precipitation ... more The aim of this study is to investigate a characteristic deformation behavior of a precipitation strengthening-type Cu-Ni-Si alloy (Cu-2.4Ni-0.51Si-9.3Zn-0.15Sn-0.13Mg) by microcompression specimens. Three micropillars with a square cross-section of 20 × 20 × 40 μm3 were fabricated by focused ion beam (FIB) micromachining apparatus and tested by a machine specially designed for microsized specimens. The three pillars were deformed complicatedly and showed different yield strengths depending on the crystal orientation. The micromechanical tests revealed work hardening by the precipitation clearly. Electron backscattered diffraction analysis of a deformed specimen showed a gradual rotation of grain axis at the grain boundaries after the compression test.

MATERIALS TRANSACTIONS, 2016

Micro-tensile tests of pure copper and a precipitation strengthening-type Cu alloy, Cu-Ni-Si allo... more Micro-tensile tests of pure copper and a precipitation strengthening-type Cu alloy, Cu-Ni-Si alloy, were performed using micro-sized tensile specimens with 10 × 10 µm 2 in cross-section and 40 µm in length and a micro-gripper, which were fabricated by a focused ion beam system. The obtained experimental results were compared with the results of Cu-Ni-Si alloy bulk sample. The micro-tensile tests of both pure Cu and Cu-Ni-Si alloy showed the typical serrations caused by moving of dislocations and a decrease of ow stress by the necking. In the Cu-Ni-Si alloy, characteristic deformation of work-hardening was observed. Electron back scatter diffraction analysis showed a gradual change in crystal orientation at the necking area.

TMS/TMS2015, 2015

The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni2Si precipitates have been... more The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni2Si precipitates have been studied. The SEM/EBSP result indicated that the nano-scale deformation twins cannot grow to micro twins during room temperature deformation. The results also revealed that the formation and growth of deformation twinning needs certain strain and stress level in the alloy aged at 723 K for 3.6k and deformed at 77 K. In contrast, it started from initial stage of deformation in the alloy aged at 723 K for 64.8 ks and deformed at 77 K. These results indicate that the deformation twinning needs certain level of stress rather than strain in precipitate strengthened Cu-Ni-Si alloy.

Lecture Notes in Business Information Processing, 2014

MATERIALS TRANSACTIONS, 2014

The work hardening behavior and deformed microstructure of the CuNiSi alloy aged at 723 K for var... more The work hardening behavior and deformed microstructure of the CuNiSi alloy aged at 723 K for various times and then deformed at 293 and 77 K were extensively investigated. The precipitate microstructure was also observed using transmission electron microscopy after aging treatment at 723 K for 0.30, 3.6, 64.8 and 345.6 ks. Deformation twins were clearly observed by transmission electron microscopy in the under-aged specimen deformed by 10% in tension at 293 K, in accordance with the enhanced work hardening rate observed during tensile deformation. The thickness of the deformation twins observed was approximately 140 nm. In addition, a significant fraction of larger deformation twins were observed by EBSD on the surface of the under-aged and peak-aged specimens tested at 77 K, for which the stressstrain behavior exhibited a nearly constant work hardening rate, i.e., high tensile strength and high elongation. These results show that the deformation twins formed during tensile deformation at 293 K contribute to strengthening of the specimen as new obstacles to the dislocation slip. Moreover, the enhanced twinning deformation at 77 K achieves high strength and elongation in the under-aged and peak-aged conditions. On the other hand, only a few deformation twins were observed in the supersaturated solid solution and over-aged specimens.

The Japan Society of Applied Physics, Feb 8, 2016

Springer eBooks, 2015

The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni2Si precipitates have been... more The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni2Si precipitates have been studied. The SEM/EBSP result indicated that the nano-scale deformation twins cannot grow to micro twins during room temperature deformation. The results also revealed that the formation and growth of deformation twinning needs certain strain and stress level in the alloy aged at 723 K for 3.6k and deformed at 77 K. In contrast, it started from initial stage of deformation in the alloy aged at 723 K for 64.8 ks and deformed at 77 K. These results indicate that the deformation twinning needs certain level of stress rather than strain in precipitate strengthened Cu-Ni-Si alloy.

Materials transactions, 2016

Micro-tensile tests of pure copper and a precipitation strengthening-type Cu alloy, Cu-Ni-Si allo... more Micro-tensile tests of pure copper and a precipitation strengthening-type Cu alloy, Cu-Ni-Si alloy, were performed using micro-sized tensile specimens with 10 × 10 µm 2 in cross-section and 40 µm in length and a micro-gripper, which were fabricated by a focused ion beam system. The obtained experimental results were compared with the results of Cu-Ni-Si alloy bulk sample. The micro-tensile tests of both pure Cu and Cu-Ni-Si alloy showed the typical serrations caused by moving of dislocations and a decrease of ow stress by the necking. In the Cu-Ni-Si alloy, characteristic deformation of work-hardening was observed. Electron back scatter diffraction analysis showed a gradual change in crystal orientation at the necking area.

Crystals, Dec 21, 2020

The aim of this study is to investigate a characteristic deformation behavior of a precipitation ... more The aim of this study is to investigate a characteristic deformation behavior of a precipitation strengthening-type Cu-Ni-Si alloy (Cu-2.4Ni-0.51Si-9.3Zn-0.15Sn-0.13Mg) by microcompression specimens. Three micropillars with a square cross-section of 20 × 20 × 40 µm 3 were fabricated by focused ion beam (FIB) micromachining apparatus and tested by a machine specially designed for microsized specimens. The three pillars were deformed complicatedly and showed different yield strengths depending on the crystal orientation. The micromechanical tests revealed work hardening by the precipitation clearly. Electron backscattered diffraction analysis of a deformed specimen showed a gradual rotation of grain axis at the grain boundaries after the compression test.

The Japan Society of Applied Physics, 2016

Cu materials are often used as micro-components in MEMS devices [1]. For applications of material... more Cu materials are often used as micro-components in MEMS devices [1]. For applications of materials in MEMS, investigating mechanical properties of micro-sized specimens is very important. Mechanical behaviors of samples with small dimensions are different from that of bulk materials, which is known that strength of the specimen is stronger when the specimen size is decreased. So, micro-mechanical test has been extensively studied since when a technique was proposed and developed by Uchic et al [2]. Based on this technical background, we have reported several studies on micro-bending [3], micro-compression [4] and micro-tensile [5] tests with a specially designed micro-testing machine. Cu-Ni-Si alloy is a precipitation strengthening-type alloy and receives a lot of attention for its high strength, high electrical conductivity and excellent bending workability [5]. However, there is still no report on micro-mechanical properties of the alloy. In this study, we report deformation behav...

Crystals, 2020

The aim of this study is to investigate a characteristic deformation behavior of a precipitation ... more The aim of this study is to investigate a characteristic deformation behavior of a precipitation strengthening-type Cu-Ni-Si alloy (Cu-2.4Ni-0.51Si-9.3Zn-0.15Sn-0.13Mg) by microcompression specimens. Three micropillars with a square cross-section of 20 × 20 × 40 μm3 were fabricated by focused ion beam (FIB) micromachining apparatus and tested by a machine specially designed for microsized specimens. The three pillars were deformed complicatedly and showed different yield strengths depending on the crystal orientation. The micromechanical tests revealed work hardening by the precipitation clearly. Electron backscattered diffraction analysis of a deformed specimen showed a gradual rotation of grain axis at the grain boundaries after the compression test.

MATERIALS TRANSACTIONS, 2016

Micro-tensile tests of pure copper and a precipitation strengthening-type Cu alloy, Cu-Ni-Si allo... more Micro-tensile tests of pure copper and a precipitation strengthening-type Cu alloy, Cu-Ni-Si alloy, were performed using micro-sized tensile specimens with 10 × 10 µm 2 in cross-section and 40 µm in length and a micro-gripper, which were fabricated by a focused ion beam system. The obtained experimental results were compared with the results of Cu-Ni-Si alloy bulk sample. The micro-tensile tests of both pure Cu and Cu-Ni-Si alloy showed the typical serrations caused by moving of dislocations and a decrease of ow stress by the necking. In the Cu-Ni-Si alloy, characteristic deformation of work-hardening was observed. Electron back scatter diffraction analysis showed a gradual change in crystal orientation at the necking area.

TMS/TMS2015, 2015

The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni2Si precipitates have been... more The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni2Si precipitates have been studied. The SEM/EBSP result indicated that the nano-scale deformation twins cannot grow to micro twins during room temperature deformation. The results also revealed that the formation and growth of deformation twinning needs certain strain and stress level in the alloy aged at 723 K for 3.6k and deformed at 77 K. In contrast, it started from initial stage of deformation in the alloy aged at 723 K for 64.8 ks and deformed at 77 K. These results indicate that the deformation twinning needs certain level of stress rather than strain in precipitate strengthened Cu-Ni-Si alloy.

Lecture Notes in Business Information Processing, 2014

MATERIALS TRANSACTIONS, 2014

The work hardening behavior and deformed microstructure of the CuNiSi alloy aged at 723 K for var... more The work hardening behavior and deformed microstructure of the CuNiSi alloy aged at 723 K for various times and then deformed at 293 and 77 K were extensively investigated. The precipitate microstructure was also observed using transmission electron microscopy after aging treatment at 723 K for 0.30, 3.6, 64.8 and 345.6 ks. Deformation twins were clearly observed by transmission electron microscopy in the under-aged specimen deformed by 10% in tension at 293 K, in accordance with the enhanced work hardening rate observed during tensile deformation. The thickness of the deformation twins observed was approximately 140 nm. In addition, a significant fraction of larger deformation twins were observed by EBSD on the surface of the under-aged and peak-aged specimens tested at 77 K, for which the stressstrain behavior exhibited a nearly constant work hardening rate, i.e., high tensile strength and high elongation. These results show that the deformation twins formed during tensile deformation at 293 K contribute to strengthening of the specimen as new obstacles to the dislocation slip. Moreover, the enhanced twinning deformation at 77 K achieves high strength and elongation in the under-aged and peak-aged conditions. On the other hand, only a few deformation twins were observed in the supersaturated solid solution and over-aged specimens.