The effect of Mg content on the mechanical properties and microstructures of GH761 alloy has been studied, and the distribution of Mg in phases has been measured, and the influence of Mg addition on the alloy and its mechanism have been analyzed. It is found that Mg in the alloy segregates in Y'-phase and minor phase, which changes the chemical compositions of Y'-phase and carbide. Furthermore, because Mg in GH761 alloy also segregates in grain boundary and the Mg atoms fill in the defect sites of grain boundary, the interface energies and the diffusion coefficient in grain 1 boundary decrease, that make the size of Y'-phase lessen and the precipitates in grain boundary become blocky. Because of the effect of Mg on the alloy microstructures, the rupture life and elongation of stress-rupture and creep strength of GH761 alloy at 650 ℃ are improved.
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