Mg-Al-Ca-Mn-Zn变形镁合金的组织和力学性能

将Mg-1Al-0.4Ca-0.5Mn-0.2Zn(质量分数，%)合金在不同温度挤压，研究其微观组织和力学性能。结果表明：在260℃和290℃挤压的合金均发生不完全动态再结晶，再结晶晶粒尺寸分别为0.75 μm和1.2 μm。二者均具有高密度的G.P.区和球状纳米析出相，能抑制位错运动并为动态再结晶提供丰富的形核位点。沿晶界析出的纳米相能抑制晶界的运动和限制再结晶晶粒的生长，从而生成尺寸为0.75 μm的超细晶粒。随着挤压温度从260℃提高到290℃，合金的屈服强度从322 MPa提高到343 MPa，伸长率分别为13.4%和13%，没有明显的变化。挤压温度的提高促进了动态析出和动态回复，使合金中积累了高密度纳米盘状相和球状相，大量位错通过动态回复转变成小角度晶界，将未再结晶区域细分成密集的层状亚晶粒，二者均能抑制新位错的运动。这些因素，是在290℃挤压后的合金仍具有较高屈服强度和塑性没有明显变化的主要原因。纳米相对位错的钉扎在一定程度上限制了动态回复的发生，使合金中仍存在较高数量的残余位错，也有利于提高其屈服强度。

Microstructure and Mechanical Properties of Extruded Mg-Alloy Mg-Al-Ca-Mn-Zn

The microstructure and mechanical properties of extruded Mg-alloy of Mg-1Al-0.4Ca-0.5Mn-0.2Zn (mass fraction, %) were systematically investigated. As indicated by the results, the incomplete dynamic recrystallization occurred for the alloys extruded at 260℃ (denoted as AXMZ1000-260) and 290°C (AXMZ1000-290) with recrystallized grain sizes of 0.75 μm and 1.2 μm, respectively. The two alloys have high-density G.P. regions and spherical nano-phases, which can effectively inhibit the dislocation motion and provide abundant nucleation sites for dynamic recrystallization. Moreover, the nano-phases precipitated along grain boundaries can restrain the migration of grain boundary and restrict the growth of DRXed grains, which results in the ultrafine grains with a size of 0.75 μm in AXMZ1000-260 alloy. The strength of the alloy decreases with the increase of extrusion temperature, and the change of elongation is not obvious. The yield strength and elongation of alloys extruded at 260℃ and 290℃ are approximately 322 MPa and 343 MPa, as well as 13.4% and 13%, respectively. The dynamic precipitation and recovery process are promoted by the increasing extrusion temperature, and a high-density G.P. zones and spherical nano-phases are accumulated in the alloy. At the same time, many dislocations are transformed into LAGBs by dynamic recovery, and the unDRXed areas are subdivided into dense lamellar subgrains. The nano-phases and LAGBs can effectively hinder the newly generated dislocation motion, which is the major reason that the alloy extruded at 290℃ still have a high yield strength and the change of ductility is not obvious. Furthermore, TEM observations show that the pinning effect of G.P. zones can impede the dynamic recovery to certain extent, resulting in a high number of residual dislocations in the alloy, which is conducive to the improvement of the yield strength.