Orientation Dependence of Fatigue Crack Propagation in Magnesium Single Crystals

Abstract

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.

An experimental study of fatigue crack propagation in extruded AZ31B magnesium alloy

“…Similar crack striation patterns were experimentally observed by Ando et al [32][33][34] in Mg single crystal having a crystal orientation identical to the idealized crystal orientation in the T-L specimen under investigation. The alternative slip mechanisms under both low and high DK values described in previous paragraph were first proposed by Ando and Tonda [32][33][34] in their study of Mg single crystal and were supported by TEM observation of dislocation pattern near the crack tip.…”

“…The alternative slip mechanisms under both low and high DK values described in previous paragraph were first proposed by Ando and Tonda [32][33][34] in their study of Mg single crystal and were supported by TEM observation of dislocation pattern near the crack tip.…”

Relationship between Fatigue Strength and Grain Size in AZ31 Magnesium Alloys

“…5,10,11) It is expected that the extruded AZ31B alloys used in this study also have the similar texture, and that the fatigue crack would propagate perpendicular to the basal plane. The notch whose plane and direction are parallel to (10 1 10) and [0001] was introduced into the Mg single crystal, and the fatigue crack propagation behaviors have been reported by Ando et al 12,13) As a result, striation-like-patterns were observed on the fracture surface. They proposed the reason why the striation-like-patterns were observed on the fracture surface in the Mg single crystal.…”

“…On the other hand, Ando et al 13) have reported that the effects of the twinning on the fatigue crack growth rate in Mg single crystals. The fatigue crack growth rate of the Mg single crystal with twinning is lower than those without twining under the fatigue test.…”

Fatigue Crack Propagation Behavior of Textured Polycrystalline Magnesium Alloys

“…Depending on their texture, wrought magnesium alloys show unique deformation behavior such as mechanical anisotropy, [2][3][4] pseudoelasticity in compression and tension loading-unloading, [4][5][6][7][8] and asymmetricity of stress-strain hysteresis loops in strain controlled low-cycle fatigue tests [9][10][11][12][13][14] and even in load controlled high-cycle fatigue tests, 4,9) etc. The orientation dependence of fatigue crack propagation behavior of magnesium single crystals, [15][16][17] and the effect of grain size [18][19][20][21] and texture [22][23][24][25] on fatigue properties of polycrystalline magnesium alloys have been reported in previous works. However, the effect of texture on the fatigue crack propagation behavior of textured polycrystalline magnesium alloys is still poorly understood.…”