| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 105 === The main purpose of this paper is using the molecular dynamics to investigate mechanical behavior of iron nanowire contains precipitate. Simulation results show, iron nanowires of <110>/<100> structure and Bi-Crystal will dominate by twin deformation in uniaxial tensile process. If iron nanowire of single crystalline contains precipitate, it will destroy perfect crystal structure of iron nanowire, resulting in reduced yield stress. When iron nanowire of Bi-Crystal contains precipitate on grain boundary, precipitate will obstruct twinning, resulting in strain and stress of yield are raised.If the interfacial bonding strength between precipitate and matrix is strong, due to precipitate and matrix have strong bonding force, in process of dislocations slip will be accompanied by high shearing stress. When dislocation bypass precipitate, it will form a dislocation loop, follow by dislocation loop will accompanied by a high shear force and shear of precipitate. If the interfacial bonding strength between precipitate and matrix is weak, due to shearing force of dislocation slipping cannot shear precipitate, the precipitate will prevent the dislocation slipping and form a dislocation loop and microvoid around the precipitate. The microvoid are stretched by stress after necking, and the microvoid will be elongate. Finally, the model break around the precipitate and form a ductile fracture feature “dimple” on the rupture surface.
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