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Published: 20-09-2019| Version 3 | DOI: 10.17632/knd8ps8hs2.3
Jian-Li Shao


Fig.1 The He number density for equilibrium He bubble at 300K. The green and red dots correspond to the unsaturated and saturated state, respectively. Fig.2 The pressure of equilibrium He bubbles with d and He/vacancy ratios at 300K. The He bubbles reach to the saturated state when He/vacancy ratios increases to 0.85 for all sizes. The pressure of unsaturated He bubbles increases as He/vacancy ratio increases, whereas the pressure of saturated He bubbles tends to be stable with some fluctuation. Fig.3 The relationship between the bubble pressure and volume at different temperatures. The Y-L equation, even considering the finite width of the interface, is no longer agrees well with the saturated He bubble unless the temperature exceeds the melting point of samples. The state of unsaturated He bubbles approximates the ideal gas EOS. A modified EOS containing the correction terms of temperature and volume is proposed to describe the saturated He bubbles. Fig.4 The variation of volume with the number of He atoms (N) . The results show a near-linear relationship between volume and the number of He atoms both in unsaturated and saturated state. The modified EOS agrees well with the MD results for N<15000. Fig.5 The relaxation process of He bubbles for different He/vacancy ratios (r) . A closed stacking fault octahedron is formed for r=1, while the closed SFO is insufficient to keep He bubble stability for r=1.5. Fig.6 The microstructure of the Al matrix induced by the equilibrium He bubbles with different initial configurations. Upper: the diameters of He bubbles are 1nm, 2nm, 3nm, 4nm and 5nm, respectively. Fig.7 The morphologies of He bubbles with d and r at 300K. Upper: the diameters are 1nm, 2nm, 3nm, 4nm and 5nm,respectively. Fig.8 The local lattice environment of He bubble on (111) plane at different temperatures. Atoms are color-coded by their local lattice structure (FCC (green), HCP (red) and disordered (white)) as obtained from dislocation extraction algorithm(DXA). The shape of He bubble shows a strong temperature dependence: (A)irregular polygon; (B)further deformation; (C)hexagon; (D)circle. Fig.9 (A)Sketch of the octahedral stress; (B)Sessile junctions obtained by removing the atoms of τ<2GPa Fig.10 The shear stress-field nephogram around He bubbles.The nephograms show the shear stress-field inhomogeneously increases as the increasing d and r. Besides, the domain of shear stress field increases as the increasing d and r. Fig.11 No dislocation atoms are found in unsaturated state. The number of dislocation atoms is nearly linear with N in saturated state.