微量Y和Ca组合添加对Mg-6Zn-1Al合金的组织和性能影响

Effect of Ca and Y on the microstructure,mechanical properties and corrosion properties of Mg-6Zn-1Al alloy

摘要:

研究了微量Y和Ca元素对Mg-6Zn-1Al合金的组织和性能影响，结果表明，铸态ZAM610合金由α-Mg、Mg51Zn20相和少量Al8Mn5相组成，单独添加Ca使Mg51Zn20相被Mg32(AlZn)49相替代，添加Y或Y+Ca，合金由α-Mg、Mg51Zn20、Al2Y相和少量的Al10Mn2Y相组成。添加Y或/和Ca，细化了镁合金再结晶晶粒，其中添加Y+Ca组合的细化效果最好。加Ca合金在挤压变形中动态析出MgZn2相，具有强烈的Zener阻滞作用，形成由细小再结晶晶粒和粗大变形带组成的双模组织。ZAMX6100合金具有最高的强度，其抗拉强度、屈服强度和伸长率，分别为354 MPa、313 MPa和17.3%。加Y合金中Al2Y相在挤压变形中促进再结晶形核，导致变形带数量减少。微合金化后镁合金力学性能的提高，可归因于动态再结晶晶粒细化、Al2Y相颗粒形成和动态析出MgZn2相。合金耐蚀性提高的原因是大量动态析出的MgZn2相阻碍了腐蚀的连续进行，而稀土Y元素提高了合金基体的耐蚀性能。

Abstract:

In this work, the effect of trace addition of Ca and Y on the microstructure, mechanical properties and corrosion properties of Mg-6Zn-1Al alloy were investigated. The results show that the second phase in the as-cast ZAM610 alloy is consisted of α-Mg, Mg51Zn20 and a small amount of Al8Mn5 phases. The Mg51Zn20 phase in the as-cast alloy is substituted by Mg32(AlZn)49 with Ca addition. α-Mg, Mg51Zn20, Al2Y and a small amount of Al10Mn2Y phases are found in the Y-containing alloys. Y or/and Ca are added to refine markedly the recrystallized grains of the tested magnesium alloys, and the alloy of Y+Ca addition has the minimum grain sizes. In the Ca-containing alloy, MgZn2 phase is dynamically precipitated during extrusion, which has strong effect of Zener retardation, and formes a double-mode microstructure composed of fine recrystallized grain and coarse deformation zone. ZAMX6100 alloy has the highest tensile strength, yield strength and elongation, which are 354 MPa, 313 MPa and 17.3%, respectively. In addition, Al2Y phase in Y-containing alloy promotes recrystallization nucleation during deformation, resulting in a reduction of deformation bands. The improvement of mechanical properties of tested alloys after microalloying can be attributed to the refinement of dynamic recrystallization grains, the formation of Al2Y phase particles and the dynamic precipitation of MgZn2 phase. For corrosion resistance of the Ca-containing alloy, the raise reason is a large amount of dynamically precipitated MgZn2 phase that prevents the continuous corrosion, while Y element increases the corrosion resistance of the alloy matrix.