通过OM, SEM和XRD等分析方法与拉伸实验研究了Sc, Zr, Er和Ti复合微合金化焊 丝合金的凝固组织及铸态力学性能, 在实现合金组织有效细化的基础上, 重点研 究了Er及Er与Ti共存对合金晶界组织及合金力学性能的影响. 结果表明, 对于Sc 和Zr复合细化的Al-Mg焊 丝合金, Er元素的存在加强了合金的细晶强化效应, 合 金的强度与塑性均得到提高, 并在合金晶 界处富集不连续分布的Al3Er共晶 相; 当Er和Ti共存于合金中时, 5-10 um的方块状(Al, Mg)20Ti2Er 金属间化合物相存在于晶界, 该相的生成会使合金的强度进一步提高, 但塑性有所 降低; (Al, Mg)20Ti2Er相和Al3Er相共存时, 两相对晶界连续性的 破坏会完全抵消Er的细化效应 对合金塑性的提高, 合金拉伸断口由混合型断裂(穿晶 断裂和沿晶断裂)转变为沿晶断裂.
The microstructure and mechanical properties of Al-Mg-Mn-Zn filler alloys microalloyed by Scandium (Sc), Zirconium (Zr) , Erbium (Er) and Titanium (Ti) were investigated with OM, SEM, SEM and tensile tests. On the basis of the effective grain refinement, the influences of Er element and coexistence of Er and Ti elements on grain boundary morphologies and phase distribution in grain boundaries, as well as their effects on the mechanical properties of experimental alloys, have been emphatically researched. The results indicate that, for the refined Al-Mg alloys by Sc+Zr, adding minor Er element can enhance the grain refinement of alloys, thus improve both the strength and ductility, and ultimately produce Al3Er phase discontinuously distributing in the grain boundaries. The combinational addition of Er and Ti elements can led to the precipitation of (Al,Mg)20Ti2Er intermetallic compound particles with 5~10μm in size and square shape, which distribute in grain boundaries and give some contribution to the improvements in both tensile strength(UTS) and yield strength(0.2YS), but lower the ductility. Coexisting of (Al,Mg)20Ti2Er and Al3Er phases breaks the grain boundary succession, consequently offsets the improvement on the ductility caused by Er grain-refining, and results in the transition of tensile fractographic patterns from the mixed-fracture (intergranular and transcrystalline fractures) to the intergranular fracture.
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