Microstructures and Properties of High-strength Alloys Severely Deformed by Machining

Tanaka, Manabu; Kato, Ryuichi; Kobayashi, Junya; Yoda, Rika

doi:10.2355/isijinternational.48.815

Cited by 5 publications

(4 citation statements)

References 27 publications

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“…8) Ni and his co-workers reported similar results on 1 100 aluminum 9) and pure Cu. 10) According to the microstructural analysis by the FE-SEM/EBSP method, 11,12) Tanaka et al 13,14) recently found that the chip specimen with γ ≈ 7.5 of the ferritic SUS430 (16Cr) steel with body-centered cubic (bcc) structure was principally composed of equiaxed submicron grains (SMGs). However, the chip specimens with shear strain (γ) up to ~10 of the 6061-T6 alloy as well as the chip specimen with γ ≈ 14 of the austenitic SUS304 (18Cr-8Ni) steel (fcc) had principally a deformed microstructure with elongated grains.…”

Section: Introductionmentioning

confidence: 99%

Microstructures of Machined Chips in Pure Titanium, Pure Iron and 0.83%C Steel

Tanaka

Fujita

2013

ISIJ Int.

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Microstructures were examined on the chip specimen of pure titanium with close-packed hexagonal (cph) structure (α-Ti, the shear strain, γ, is ~22), and those of pure iron (α-Fe, γ ≈ 7.5) and 0.83%C steel which had originally pearlite structure (γ ≈ 7.5) with body-centered cubic (bcc) structure by the FE-SEM/ EBSP method and optical microscopy. The hardness of the chip specimens was also measured and compared to that of the original materials. UFGed materials could be produced at relatively small shear strain (~7.5) in pure iron and 0.83%C steel. The average grain diameter of the chip specimen was slightly larger in the 0.83%C, because lamellar cementite phase in original pearlite structure hindered the formation of submicron grains. The hardness of the chip specimens increased with increasing shear strain, and the hardness of the chip specimen with γ ≈ 7.5 (391 Hv) was ~4 times as much as that of the original material (93.9 Hv) in pure iron. However, it was impossible to produce the ultra-fine grained materials by machining of α-Ti even at γ ≈ 22. According to the experimental results obtained so far, the number of slip systems (crystal structure) as well as shear strain seems to be one of the important factors controlling the generation of equiaxed submicron grain structure. Higher stacking fault energy is favorable for cross-slip or climb of dislocations in dynamic recovery which probably governs the generation of submicron grains.

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Section: Introductionmentioning

confidence: 99%

Microstructures of Machined Chips in Pure Titanium, Pure Iron and 0.83%C Steel

Tanaka

Fujita

2013

ISIJ Int.

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“…19) Figure 5 summarizes the result of crystallographic analysis on the chip specimens with γ ≈ 10 and γ ≈ 22 of the Inconel X-750 alloy. The analyzed area is 20 μm × 20 μm (Fig.…”

Section: Inconel X-750 Alloymentioning

confidence: 99%

“…A rough estimation of shear strain was also made using the above equations for a chip specimen of the Inconel X-750 alloy (γ ≈ 3) produced under the non two-dimensional cutting condition in the previous study. 19) In order to produce chip specimens with the same microstructure by machining, it is necessary to control the cutting conditions with or without usage of cutting fluid. The works should be machined using cutting tools of the same material, and the rake angle, the cutting depth, the feed and the cutting speed should be kept constant during cutting process.…”

Section: Materials and Production Of Chip Specimensmentioning

confidence: 99%

“…However, the analysis by the FE-SEM/EBSP method (an orientation imaging microscopy, OIM) 17,18) revealed that most of grain boundaries (~70%) are small angle grain boundaries (θ <5°) in the chip specimen with a shear strain (γ ) of ~4 of the 6061-T6 alloy produced by machining. 19) Thus, it seems necessary to examine a wide area by the FE-SEM/EBSP method in order to characterize the grain structures of chip specimens.…”

Section: Introductionmentioning

confidence: 99%

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Microstructures of Cutting Chips of SUS430 and SUS304 Steels, and NCF 750 and 6061-T6 Alloys

et al. 2011

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Microstructures of chip specimens of high-strength materials produced by machining were examined by FE-SEM/EBSP method (an orientation imaging microscopy, OIM). In the ferritic SUS430 (16Cr) steel, the chip specimen with shear strain (γ) of ~7.5 was principally composed of equiaxed submicron grains which were for the most part surrounded by large angle grain boundaries (misorientation, θ ≥15°). A similar microstructure was observed in the chip specimen with γ ≈ 22 of the Inconel X-750 (NCF 750) nickel-base alloy. However, the chip specimen of the austenitic SUS304 (18Cr-8Ni) steel (γ ≈ 14) and that of the 6061-T6 (aluminum) alloy (γ ≈ 10) exhibited principally a deformed microstructure with elongated grains and sub grains separated by small angle (2°≤θ <5°) or medium angle grain boundaries (5°≤θ <15°), although equiaxed submicron grains were partly observed. The chip specimens exhibited very high hardness compared to the original materials except 6061-T6 alloy. The maximum hardness value (609 Hv) was observed in the chip specimen with γ ≈ 22 of the Inconel X-750 alloy. Strong particles with equiaxed submicron grain structure, which can be easily produced by milling of cutting chips of commercial alloys, will be potential strengthener for metal matrix composites.

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