Relevance of instrumented nano-indentation for the assessment of the mechanical properties of eutectic crystals and α-Al grain in cast aluminum alloys

Okayasu, Mitsuhiro; Takasu, Satoshi; Mizuno, Mamoru

doi:10.1007/s10853-011-5791-2

Cited by 16 publications

(10 citation statements)

References 12 publications

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“…The material properties of the eutectic phase were determined on the basis of the applied load vs deformation relationships, measured using a dynamic ultra-micro-hardness tester (DUH-211 Shimadzu). [15,16] This tester can measure the mechanical properties in a small region on the specimen surface. Because of the greater hardness of the eutectic phase compared to the Al matrix phase, arising from the hard Fe-and Si-based structures, the Poisson ratio for the eutectic phase was determined to be 0.3, while that for Al matrix was 0.33.…”

Section: B Experimental Detailsmentioning

confidence: 99%

“…In fact, in some associated samples, cracks did not grow through the artificial defect of /0.25 mm for GC samples (see Figure 13(d)). One of the present authors has examined the hardness of eutectic structures in ADC12 aluminum alloys using an ultra-microhardness tester, in which high Martens hardness value of 6.36 GPa for the Al-Fe-based eutectic structures, [15] φ0.25 φ0.25 which are about 8 times higher than the hardness of the a-Al phase (0.8 GPa). To verify this, direct observation of the fracture surfaces was conducted.…”

Section: Strain Characteristicsmentioning

confidence: 99%

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The Effects of Defects on Tensile Properties of Cast ADC12 Aluminum Alloy

Okayasu

Sakai

2015

Metall Mater Trans A

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To better understand the effects of cast defects on mechanical properties, cast aluminum alloys with various porosities were used. Porosity in the cast samples was created during the casting process, and to clearly identify the porosity effects on the mechanical properties, artificial defects (porosity-like tiny holes) were created mechanically. The tensile properties for the cast aluminum alloys appear to be attributed to the area fraction of the porosity on the fracture surface (namely, the defect rate, DR), although there were different trends because of the different stress concentrations: the ultimate tensile strength and 0.2 pct proof strength were linearly related to DR, while a non-linear correlation was detected for fracture strain. Even in Al alloys with small amounts of defects, significant reductions in the fracture strain were observed. These results were verified using tensile tests on specimens containing artificial defects. The effects of artificial defects on the tensile properties were further investigated using numerous tiny holes, created in several formations. The artificial defects (several small holes), lined up at perpendicular (90 deg) and 45 deg directions against the loading direction, made significant reductions in the tensile properties, even though only weak defect effects were observed for the 90 deg loading direction. No severe defect effects were obvious for the specimen with a tiny defect of /0.1 mm, because of the lower stress concentration, compared to the microstructural effects in the cast Al alloys: the grain boundaries and the second phases. Such phenomena were clarified using tensile tests on cast samples with differently sized microstructures. There were no clear defect effects on the yield strength as the defect amount was less than 10 pct, and microstructural effects were not detected either in this case. Failure characteristics during tensile loading were revealed directly by in-situ strain observations using high-speed cameras.

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Section: B Experimental Detailsmentioning

confidence: 99%

Section: Strain Characteristicsmentioning

confidence: 99%

The Effects of Defects on Tensile Properties of Cast ADC12 Aluminum Alloy

Okayasu

Sakai

2015

Metall Mater Trans A

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“…The differences in the size of α-Al grain among the cast samples can no longer be detected clearly after the aging process, although a comparison of HMC sample I and HMC sample II shows a slightly different size of the eutectic phases: the larger eutectic phases are obtained for the sample with the longer aging time. [15]. From Fig.…”

Section: Mechanical and Microstructural Examinationsmentioning

confidence: 97%

Precise analysis of effects of aging on mechanical properties of cast ADC12 aluminum alloy

Okayasu

2015

Materials Science and Engineering: A

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“…Small primary a-Al size implies that the structure is fine, with the associated benefits including better distributed porosity and finer intermetallics [19]. All of these metallurgical changes of the structure are responsible for the good mechanical properties.…”

Section: Characteristics Of Primary A-al Phasementioning

confidence: 99%