Influence of Sb and Sr Modification on Microstructure and Tensile Properties of Al-5.5Mg-2.5Si-0.6Mn Alloy
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摘要:
以Al-5.5Mg-2.5Si-0.6Mn免热处理铸造合金为研究对象,分别研究了锑（质量分数0.20%）单一变质、锑（质量分数0.20%）和锶（质量分数0.03%,0.05%,0.10%）复合变质对Al-Mg-Si合金组织和拉伸性能的影响。结果表明：锑单一变质后,试验合金中的初生α-Al相由变质前的等轴状变为枝晶形貌,平均尺寸增大,Al-Mg2Si共晶组织仍保持细小的纤维状；锑和锶复合变质后,α-Al相枝晶尺寸变大,共晶组织由纤维状变为迷宫状,当锶的质量分数达到0.05%时,共晶组织变质完全,且随着锶质量分数由0.03%增加到0.10%,α-Al相尺寸和共晶组织的层片间距先增大后减小。与未变质合金相比,锑单一变质后试验合金的抗拉强度和断后伸长率分别提升了6.0%和63.3%；拉伸断口中存在大量细小的韧窝,呈典型的韧性断裂特征,该合金的拉伸性能最好。锑和锶复合变质后,拉伸性能出现较大幅度的下降,且随着锶含量的增加,抗拉强度和断后伸长率均先升后降；拉伸断口由解理面、缩孔和裂纹组成。锑的单一变质效果优于锑和锶的复合变质效果。
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关键词:
- Al-Mg-Si合金 /
- 免热处理 /
- 复合变质 /
- 显微组织 /
- 拉伸性能
Abstract:Taking Al-5.5Mg-2.5Si-0.6Mn non-heat-treated cast alloy as research object, the effects of single modification with Sb (0.20wt%) and composite modification with Sb (0.20wt%) and Sr (0.03wt%, 0.05wt%, 0.10wt%) on the microstructure and tensile properties of Al-Mg-Si alloy were studied. The results show that after the single modification of Sb, the primary α-Al phase in the test alloy changed from equiaxed shape before modification to dendritic morphology, with an increase in average size, and the Al-Mg2Si eutectic structure still maintained a fine fibrous shape. After the composite modification of Sb and Sr, the dendritic size of the α-Al phase increased, and the eutectic structure changed from fibrous shape to labyrinthine shape. When the mass fraction of Sr reached 0.05%, the eutectic structure was completely modified, and as the Sr mass fraction increased from 0.03% to 0.10%, the size of the α-Al phase and the interlayer spacing of the eutectic structure first increased and then decreased. Compared with those of the unmodified alloy, the tensile strength and percentage elongation after fracture of the test alloy after the single modification of Sb increased by 6.0% and 63.3%, respectively; there were numerous small ductile dimples in the tensile fracture, exhibiting typical ductile fracture characteristics, and the alloy had the best tensile properties. After the composite modification of Sb and Sr, the tensile properties showed a significant decrease, and with the increase of Sr content, the tensile strength and percentage elongation after fracture first increased and then decreased; the tensile fracture was composed of cleavage planes, shrinkage cavities and cracks. The single modification effect of Sb was superior to the composite modification effect of Sb and Sr.
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Keywords:
- Al-Mg-Si alloy /
- non-heat treatment /
- composite modification /
- microstructure /
- tensile property
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