Al含量对Zn-xAl-4Sb合金平衡凝固组织的影响

Effect of Al contents on equilibrium solidification microstructure of Zn-xAl-4Sb alloys used for hot-dip galvanizing

利用SEM、EDS、XRD研究了不同Al含量的Zn-xAl-4Sb(x=0、0.5、1.0、2.0、4.0、6.0)合金在炉冷条件下(冷却速度0.04℃/s)的凝固组织,探讨了Al和Sb以Zn-Al-Sb三元中间合金加入锌液的可能性.结果表明:合金中的Al优先与Sb生成AlSb相;当Al含量小于1.0%时,随着Al含量的增加,合金中AlSb相的量增加,β-Sb3Zn4相逐渐减少;当Al含量为1.0%时,β-Sb3Zn4相消失,合金组织为Zn基体上分布AlSb相;当Al含量大于1.0%时,合金中出现Zn-Al共晶,且共晶的量随Al含量的增加而增多;用Zn-Al-Sb室温下等温截面的富锌角表示了Zn-xAl-4Sb体系的室温相组成.因Al和Sb形成高熔点AlSb相,很难在锌液中溶解,故Al和Sb不宜以Zn-Al-Sb三元中间合金的方式加入.

The solidification microstructures of Zn-xAl-4Sb（x=0,0.5,1.0,2.0,4.0,6.0） under furnace cooling condition（cooling rate is about 0.04 ℃/s） were examined by SEM,EDS and XRD.The feasibility of the adding Al and Sb in the form of Zn-Al-Sb ternary master alloy was discussed.The results show that Al combines preferentially with Sb,forming AlSb intermetallic compound.When the content of Al is less than 1.0%,the amount of AlSb intermetallic compound is increased,and the amount of β-Sb3Zn4 intermetallic compound is reduced with the increase of Al content.When the content of Al is 1.0%,the β-Sb3Zn4 intermetallic compound vanishes,and the microstructure is characterized by a mass of AlSb grains surrounded by a Zn matrix.When the content of Al is larger than 1.0%,Zn-Al eutectic microstructure appears,and the amount of Zn-Al eutectic is increased with the increase of Al content.The Zinc-rich corner of Zn-Al-Sb ternary phase diagram at ambient temperature is sketched to illustrate the phase compositions of these Zn-xAl-4Sb alloys.Because Al and Sb can be combined as intermetallic AlSb with high melting point,which is hard to dissolve in zinc bath.Therefore,it is not recommended that the addition of Al and Sb into zinc bath is in the form of Zn-Al-Sb ternary master alloy