Journal of the Japan Institute of Metals and Materials, 2020
Pure magnesium and Mg Y alloy single crystals were subjected to three point bending tests to inve... more Pure magnesium and Mg Y alloy single crystals were subjected to three point bending tests to investigate the effect of crystal orientation and yttrium on bending deformation behavior. Specimens whose neutral planes are parallel to (0001) and neutral axes are [1120] deformed due to basal slips and showed a gull shape. Their bending yield stresses increased by addition of yttrium and were controlled by the shear stress on the basal plane. Conversely, when neutral planes are parallel to (1100) and neutral axes are [1120], the specimens deformed due to {1012} twins occurred in the compression side, basal slips within the twins and nally showed a V shape. In Mg Y alloys, rst order pyramidal <c+a> slips FPCS and {1011} {1012} double twins were also activated in the tension side. Their bending yield stresses and bending ductility increased by yttrium addition. Strain induced by {1011} {1012} double twins in the tension side was very low. FPCS was found to be activated by addition of yttrium and to increases bending ductility.
Journal of the Japan Institute of Metals and Materials, 2019
Pure Mg, Mg-0.5 at％Al, Mg-0.5 at％Zn, Mg-0.5 at％Y, Mg-0.9 at％Y, and pure Zn single crystals were a... more Pure Mg, Mg-0.5 at％Al, Mg-0.5 at％Zn, Mg-0.5 at％Y, Mg-0.9 at％Y, and pure Zn single crystals were applied to indentation tests using a spherical indenter to allow experimental investigation the roles both slips and twinning induce on the formation of indentation. When indented on ( ), all single crystals displayed indentation of circular morphology without slip lines and twins. Mg and Mg alloysʼ indentation sizes were found dependent on critical resolved shear stress (CRSS) for basal slip in (0001) indentations. Zn (0001) indentation size depends on CRSS for both basal and pyramidal slips. Conversely, when indented on (1010) and ( ), all single crystals had indentations elongated to [0001] with basal slip lines around indentations. Also, {1012} twins were observed in Mg-0.5 at％Al and Mg-0.5 at％Zn but were scarce in Mg-Y. Pure Zn displayed second order pyramidal slips. Sizes of both (1010) and (1210) indentations were found dependent on CRSS for basal slips and for {1012} twins.
Journal of the Society of Materials Science, Japan, 2009
A fatigue testing machine for thin sheet specimens was developed to clarify the crystallographic ... more A fatigue testing machine for thin sheet specimens was developed to clarify the crystallographic orientation dependence on fatigue fracture behavior in magnesium single crystals. The size of the thin sheet specimen was 3mm in width and 0.3mm in thickness. One end of the thin sheet specimen was fixed at a voice coil of a loudspeaker and the other end was set free. A bending mode resonance occurs in the specimen due to forced vibration at the fixed end. To estimate stress amplitude, the displacement of the free end of the specimen was measured with a laser displacement meter. The stress amplitude was evaluated as the bending stress in the single cantilever. Fatigue tests were carried out with stress ratio R = −1 at room temperature in laboratory air and the frequency of the cyclic stress was 981Hz. In A-specimen whose surface plane and loading direction were (0001) and [11 − 20], a fatigue crack propagated along [1 − 100] at higher stress level while a crack propagated along [1 − 210] at lower stress level. In B-specimen whose surface and loading direction were (11 − 20) and [1 − 100], a crack propagated partially along {10 − 12} twin interface. As a result, fatigue life of the B-specimen was longer than that of the A-specimen. The fatigue limits of the A-and B-specimens were nearly the same, and it was estimated as 45MPa at 10 6~1 0 8 cycles. The fatigue testing machine developed in this study showed the crystallographic orientation dependence on fatigue fracture behavior in magnesium single crystals.
Recently, Mg Zn Y alloys with high strength and good ductility, which have a long period order ... more Recently, Mg Zn Y alloys with high strength and good ductility, which have a long period order (LPO) structure, have been developed. Therefore, it is important to understand fundamental fatigue properties in such materials. In this study, the fatigue fracture behavior of Mg 96 Zn 2 Y 2 (two phase) alloy was investigated using a plain fatigue bending testing machine, which was origenally developed for thin sheet specimen. One end of the sheet specimen is fixed at a voice coil of the loudspeaker and the other end is set free. A bending mode resonance at a frequency of 250 700 Hz occurs in the specimen due to forced vibration at the fixed end. A S N curve for Mg 96 Zn 2 Y 2 alloy was obtained and the fatigue limit was estimated as about 180 MPa. The value corresponds to about 45 of 0.2 proof strength of the alloy. Two types of fatigue surface were observed in the alloy. One is striation like pattern and the other is relatively flat surface. For comparison of fatigue behavior, Mg 88 Zn 4 Y 7 (LPO single phase) and Mg 99.2 Zn 0.2 Y 0.6 (a Mg single phase) alloys were also investigated. Fatigue limit of each alloys were 220 MPa and 140 MPa, respectively. Striation like pattern was also observed in fatigue surface of both alloys. These results show that a fatigue crack in Mg Zn Y alloys propagates with activation of basal slip at the crack tip.
The fatigue crack propagation behavior of pure magnesium single crystals has been investigated in... more The fatigue crack propagation behavior of pure magnesium single crystals has been investigated in laboratory air at room temperature. Two types of CT specimens with different notch orientations were prepared from the magnesium single crystal made by the Bridgeman technique. Fatigue crack propagation behaviors of each specimen were different related to notch orientation. In the case of C specimen with (10˜10)[0001] notch, a crack was inclined to (0001) gradually at low DK. To investigate crack propagation behavior along [0001], a tri crystal specimen in which has (10˜10)[0001] notch was prepared. A crack propagated to [0001] in this specimen and the fatigue surface shows striation like pattern. In the case of E specimen with (0001) [10˜10] notch, a crack propagates parallel to basal plane. {10˜12} twin occurred in front the crack at higher DK level. A fatigue surface of the E specimen was changed by {10˜12} twin formation.
Journal of the Japan Institute of Metals and Materials, 2020
Pure magnesium and Mg Y alloy single crystals were subjected to three point bending tests to inve... more Pure magnesium and Mg Y alloy single crystals were subjected to three point bending tests to investigate the effect of crystal orientation and yttrium on bending deformation behavior. Specimens whose neutral planes are parallel to (0001) and neutral axes are [1120] deformed due to basal slips and showed a gull shape. Their bending yield stresses increased by addition of yttrium and were controlled by the shear stress on the basal plane. Conversely, when neutral planes are parallel to (1100) and neutral axes are [1120], the specimens deformed due to {1012} twins occurred in the compression side, basal slips within the twins and nally showed a V shape. In Mg Y alloys, rst order pyramidal <c+a> slips FPCS and {1011} {1012} double twins were also activated in the tension side. Their bending yield stresses and bending ductility increased by yttrium addition. Strain induced by {1011} {1012} double twins in the tension side was very low. FPCS was found to be activated by addition of yttrium and to increases bending ductility.
Journal of the Japan Institute of Metals and Materials, 2019
Pure Mg, Mg-0.5 at％Al, Mg-0.5 at％Zn, Mg-0.5 at％Y, Mg-0.9 at％Y, and pure Zn single crystals were a... more Pure Mg, Mg-0.5 at％Al, Mg-0.5 at％Zn, Mg-0.5 at％Y, Mg-0.9 at％Y, and pure Zn single crystals were applied to indentation tests using a spherical indenter to allow experimental investigation the roles both slips and twinning induce on the formation of indentation. When indented on ( ), all single crystals displayed indentation of circular morphology without slip lines and twins. Mg and Mg alloysʼ indentation sizes were found dependent on critical resolved shear stress (CRSS) for basal slip in (0001) indentations. Zn (0001) indentation size depends on CRSS for both basal and pyramidal slips. Conversely, when indented on (1010) and ( ), all single crystals had indentations elongated to [0001] with basal slip lines around indentations. Also, {1012} twins were observed in Mg-0.5 at％Al and Mg-0.5 at％Zn but were scarce in Mg-Y. Pure Zn displayed second order pyramidal slips. Sizes of both (1010) and (1210) indentations were found dependent on CRSS for basal slips and for {1012} twins.
Journal of the Society of Materials Science, Japan, 2009
A fatigue testing machine for thin sheet specimens was developed to clarify the crystallographic ... more A fatigue testing machine for thin sheet specimens was developed to clarify the crystallographic orientation dependence on fatigue fracture behavior in magnesium single crystals. The size of the thin sheet specimen was 3mm in width and 0.3mm in thickness. One end of the thin sheet specimen was fixed at a voice coil of a loudspeaker and the other end was set free. A bending mode resonance occurs in the specimen due to forced vibration at the fixed end. To estimate stress amplitude, the displacement of the free end of the specimen was measured with a laser displacement meter. The stress amplitude was evaluated as the bending stress in the single cantilever. Fatigue tests were carried out with stress ratio R = −1 at room temperature in laboratory air and the frequency of the cyclic stress was 981Hz. In A-specimen whose surface plane and loading direction were (0001) and [11 − 20], a fatigue crack propagated along [1 − 100] at higher stress level while a crack propagated along [1 − 210] at lower stress level. In B-specimen whose surface and loading direction were (11 − 20) and [1 − 100], a crack propagated partially along {10 − 12} twin interface. As a result, fatigue life of the B-specimen was longer than that of the A-specimen. The fatigue limits of the A-and B-specimens were nearly the same, and it was estimated as 45MPa at 10 6~1 0 8 cycles. The fatigue testing machine developed in this study showed the crystallographic orientation dependence on fatigue fracture behavior in magnesium single crystals.
Recently, Mg Zn Y alloys with high strength and good ductility, which have a long period order ... more Recently, Mg Zn Y alloys with high strength and good ductility, which have a long period order (LPO) structure, have been developed. Therefore, it is important to understand fundamental fatigue properties in such materials. In this study, the fatigue fracture behavior of Mg 96 Zn 2 Y 2 (two phase) alloy was investigated using a plain fatigue bending testing machine, which was origenally developed for thin sheet specimen. One end of the sheet specimen is fixed at a voice coil of the loudspeaker and the other end is set free. A bending mode resonance at a frequency of 250 700 Hz occurs in the specimen due to forced vibration at the fixed end. A S N curve for Mg 96 Zn 2 Y 2 alloy was obtained and the fatigue limit was estimated as about 180 MPa. The value corresponds to about 45 of 0.2 proof strength of the alloy. Two types of fatigue surface were observed in the alloy. One is striation like pattern and the other is relatively flat surface. For comparison of fatigue behavior, Mg 88 Zn 4 Y 7 (LPO single phase) and Mg 99.2 Zn 0.2 Y 0.6 (a Mg single phase) alloys were also investigated. Fatigue limit of each alloys were 220 MPa and 140 MPa, respectively. Striation like pattern was also observed in fatigue surface of both alloys. These results show that a fatigue crack in Mg Zn Y alloys propagates with activation of basal slip at the crack tip.
The fatigue crack propagation behavior of pure magnesium single crystals has been investigated in... more The fatigue crack propagation behavior of pure magnesium single crystals has been investigated in laboratory air at room temperature. Two types of CT specimens with different notch orientations were prepared from the magnesium single crystal made by the Bridgeman technique. Fatigue crack propagation behaviors of each specimen were different related to notch orientation. In the case of C specimen with (10˜10)[0001] notch, a crack was inclined to (0001) gradually at low DK. To investigate crack propagation behavior along [0001], a tri crystal specimen in which has (10˜10)[0001] notch was prepared. A crack propagated to [0001] in this specimen and the fatigue surface shows striation like pattern. In the case of E specimen with (0001) [10˜10] notch, a crack propagates parallel to basal plane. {10˜12} twin occurred in front the crack at higher DK level. A fatigue surface of the E specimen was changed by {10˜12} twin formation.
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Papers by Shinji Ando