高强变形镁合金通常都是通过第二相强化提高合金强度，但高体积分数的第二相常导致合金塑性降低。为开发低成本高强韧低合金镁合金，本项目基于溶质晶界偏聚工程，对含Ca的低合金镁合金，利用温挤压变形以及晶界偏聚对再结晶晶粒长大的抑制作用，制备亚微米超细晶低合金镁合金；同时通过溶质晶界偏聚提高晶界结合强度，弱化织构；充分利用亚微米超细晶的细晶强化和溶质晶界偏聚强化，开发新型含晶界偏聚的超细晶高强韧低合金Mg-Ca-(Zn/Al)镁合金。研究合金成分、温挤压变形和热处理工艺对晶界偏聚的影响规律，调控镁合金的晶界偏聚行为；揭示溶质晶界偏聚与超细晶和弱织构形成的作用机理；阐明晶界偏聚对晶界结合及超细晶低合金高强韧镁合金的强韧性的影响规律和机理。本项目将发展具有镁合金特色的溶质原子晶界偏聚强韧化理论，为开发新型超细晶高强韧镁合金提供一条新途径。

The development of high-strength wrought magnesium alloys are mostly based on second phase strengthening. However, High density of second phases usually leads to reduced ductility. In this proposal, we develop new high-strength-low-alloy magnesium alloys based on the solute grain boundary segregation engineering. The Ca containing Mg alloys will be used since the Ca has the great grain boundary segregation tendency. The ultrafine-grained Mg alloys will be produced since the warm extrusion is applied and the inhibition of grain growth during dynamic recrystallization by solute grain boundary segregation. In addition, the solute grain boundary segregation leads to the increased grain boundary bond strength and random crystallographic texture of the magnesium alloys. In this project, the new ultrafine-grained high-strength low-alloy Mg-Ca-(Zn/Al) magnesium alloys will be developed by taking full advantage of fine-grain strengthening induced by ultrafine grains and solute grain boundary segregation strengthening. The effect of alloy composition, warm extrusion processing and annealing parameters on the grain boundary segregation will be characterized to control the solute grain boundary segregation behavior. The interaction between grain boundary segregation and formation of ultrafine grains and random texture will be clarified. The effect of grain boundary segregation on grain boundary bond strength will be revealed, and the strengthening and toughening mechanism of the ultrafine-grained high-strength low-cost alloys will be established. The research will develop a new alloy design theory for high-strength low-alloy Mg alloys based on solute grain boundary segregation strengthening and toughening and open a new path for the develop of low cost ultrafine-grained high-strength low-cost Mg alloys.