日本金属学会誌
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
論文
Ti3SiC2-MAX相におけるクリープ変形に伴うキンク形成とキンク強化の可能性
松井 大輝森田 孝治寺田 大将池田 賢一三浦 誠司
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2021 年 85 巻 12 号 p. 439-448

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Kink formation and kink strengthening mechanisms were examined in the polycrystalline Ti3SiC2-MAX phase prepared by a spark-plasma-sintering technique. The creep behavior tested by compression at 1200℃ showed two deformation regions depending on the applied stresses; at lower stresses of <120 MPa, the stress exponent n exhibited ≈1.8, whereas at higher stresses, it exhibited n ≥ 6.0. The creep behavior can be ascribed to grain boundary sliding mechanism for the lower stresses with n ≈ 1.8 and dislocation-related creep mechanisms for the higher stresses with n ≥ 6.0. The kink bands were frequently observed to form in the grains deformed only at the higher stresses when its basal plane inclined by about 10-20° against the compressive axis. This suggests that the kink bands might be formed only when two factors of the large stresses acting on the basal plane and the resultant dislocation activities were satisfied. Nanoindentation tests conducted around the formed kink boundaries showed that the hardness increased linearly with decreasing in the distance from the kink boundaries and showed higher values around the kink boundaries. Since the kink boundaries blocked the slip line caused by the nanoindentation, those become a resistance against the dislocation motion caused by the indentation deformation. This suggests that the kink boundaries would be contributed to improve the mechanical properties of the Ti3SiC2-MAX phase.

(a) Low magnification SPM image of nanoindentations #0-#9 tested at the kink-formed grain; the arrows indicate kink boundaries of KB① and KB②. (b) Enlarged SPM image of the nanoindentations #2 and #4. (c) Nanohardness Hn plotted as a function of the distance L from the nearest kink boundary (KB) along the basal plane. Fullsize Image
 
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