关键词: 低稀土, 镁合金, 时效, 弥散析出, 强化

Abstract: High-strength rare-earth magnesium alloys have broad application prospects in aerospace, transportation and other fields. However, conventional methods obtaining high-strength magnesium alloys by increasing rare-earth contents raise material production costs. Therefore, there is an urgent need to develop a high-strength, low-cost magnesium alloy with low rare-earth content. The evolution of microstructure and properties of the Mg-5.3Gd-4.1Y-0.13Zr solid-solution magnesium alloy during rolling deformation and aging processes is investigated. The contribution of each strengthening mechanism is calculated, with a focus on the unique precipitation strengthening mechanism at peak aging. The results indicate that the cubic compound Mg₅(GdY), which exists throughout the entire aging period, is primarily distributed along the grain boundaries. Its size ranges from 40 nm to 300 nm, and it is relatively soft with poor strengthening effect. During peak aging, 2～6 nm ellipsoidal precipitates are observed to be finely dispersed within the matrix. Due to the relatively low rare-earth content, these precipitates only nucleate and do not grow, contributing significantly to the strengthening of the alloy. At peak aging, the alloy’s yield strength reached 341.14 MPa, with a contribution from precipitation strengthening of 159 MPa, accounting for 47% of the total. The ultimate tensile strength reached 504.40 MPa, which is superior to most Mg-Gd and Mg-Gd-Y alloy systems. This is a novel method for obtaining high-strength magnesium alloys under low rare-earth content by controlling the nucleation and growth behavior of the precipitates, thereby regulating their morphology and distribution. This approach provides new principles and ideas for designing and developing high-strength rare-earth magnesium alloys through precipitation control.

Key words: low rare earth, magnesium alloy, aging, dispersion precipitation, strengthening