《Table 2 Calculated enthalpy (H0) of solution at infinite dilution (k J/mol) [24]》

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《微量In对Al-Cu-1.0Li-(Mg)合金微观组织与拉伸性能的影响（英文）》

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At T6 aging，the role of In independent addition in causingthe formation of cubic?precipitates is weakened or suppressed by the In+Mg combined addition，which promotes the uniform and concentrated precipitation of T1 phases instead.It is known that Al possesses a higher stacking fault energy，but Mg elements can assemble on the close-packed surface of{111}Al to decrease the stacking fault energy[6，7].Therefore，as a small amount of Mg is added to Al-Cu-Li alloy，considerable stacking faults are formed.These stacking faults provide beneficial sites for T1 heterogeneous nucleation，because the energy barrier for T1 nucleation is lowered at the stacking faults.Besides，there exists strong interaction between Mg and In，between Li and In，and between Mg and Cu，as predicted by the calculated enthalpies of solution at infinite dilution，?H0.Table 2 shows some extracted values of?H0 from the lists reported by Niessen et al[24].In the solutionized alloy，Mg and In atoms assemble on the close-packed surface of{111}Al，forming Mg-In atom co-clusters due to their strong interaction.Then，at the early aging stage，Li atoms and Cu atoms are attracted to Mg-In atom co-clusters，due to strong interaction between Li and In atoms and between Cu and Mg atoms.That is to say，as small Mg and In are simultaneously added，the formed stacking faults assembled with Mg atoms provide the sites for T1 heterogeneous nucleation，and Mg-In atom co-clusters act as catalysis and bridge for promoting the diffusion of Cu and Li atoms to the stacking faults.Therefore，the precipitation of T1 is significantly promoted，but that of the?phase is suppressed.Because the strengthening effect of T1 phase precipitated at{111}Al plane is higher than that of other phases[25]，the strength of the Al-Cu-Li alloy with In+Mg combined addition is correspondingly enhanced，compared to that of the alloy with In independent addition.