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A Phenomenological micromechanical model of FCC metals under radiation induced crystal defects

照射誘起結晶欠陥を有するFCC金属の現象論的微小力学モデル

青柳 吉輝; 都留 智仁  ; 加治 芳行 

Aoyagi, Yoshiteru; Tsuru, Tomohito; Kaji, Yoshiyuki

本研究では、照射誘起結晶欠陥の情報を導入した照射欠陥-結晶塑性モデルを構築することを目的とし、照射によって誘起された不完全転位ループ密度及び積層欠陥四面体密度の情報を結晶塑性論における硬化係数に導入した。その際に、転位運動に起因する不完全転位ループの消失も考慮した。結晶塑性解析に用いる照射欠陥の影響を表す数値係数を分子動力学法を用いた数値解析によって同定した。本モデルを用いてCu単結晶平板を想定した単純引張条件下における3次元結晶塑性有限要素法解析を行い、初期照射欠陥密度の増加に伴う降伏応力の上昇並びに加工硬化率の減少を再現した。また、照射欠陥密度が最も高いものでは、降伏後の軟化が現れ、照射欠陥の存在が変形の局所化に影響を与えるといった知見を得た。

In this study, we construct a new crystal plasticity model considering densities of crystal defects induced by irradiation. Evolution equation of densities of imperfect dislocation loop is proposed by considering disappearance of imperfect dislocation loops originated in dislocation movement. Moreover, in order to predict increase of CRSS due to irradiation and decrease of work-hardening ratio, information of densities of imperfect dislocation loop and stacking fault tetrahedron are introduced into a hardening modulus of crystal. Value of controlling parameters operating effect of crystal defects on flow stress are decided by a MD simulation. We conduct a crystal plasticity simulation for simple tension of polycrystal using the presented model. The macroscopic stress-strain responses such as increase of yield stress and decrease of work-hardening ratio due to irradiation are numerically predicted. We investigate comprehensively the effect of behaviors of crystal defects on the mechanical property of irradiated materials and the generation of dislocation substructures depending on mechanical conditions.

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