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在450℃镀锌条件下,锌浴中加入质量分数为0.2%的Al,采用SEM观察镀层的结构特征,利用EDS定量分析相的微区成分,利用其线扫描和面扫描定性分析镀层截面元素变化情况.借助Miedema模型和Toop模型,计算了镀层中各二元Fe-Al,Fe-Zn和三元Fe_2Al_5Znx(h)金属间化合物(IMC)的热力学值,分析了随镀锌时间的延长,出现Fe_2Al_5抑制层失稳破坏而产生Fe-Zn反应的根本原因.结果表明,因为Fe-Al IMC比Fe-Zn IMC具有更稳定的热力学性质,钢基体与锌浴界面优先产生连续的Fe_2Al_5金属间化合物抑制层,抑制Fe-Zn反应,但随镀锌时间的延长,Fe_2Al_5的失稳破坏丧失对Fe-Zn反应的抑制作用,生成Fe Zn10(d)相.Fe_2Al_5抑制层的失稳机制有两种:一种是Fe_2Al_5/锌浴界面处Al的局部贫化导致Zn对Fe_2Al_5的侵蚀,形成Fe_2Al_5Znx,造成系统热力学稳定性降低,从而导致Fe_2Al_5被Zn侵蚀分解,同时在Fe_2Al_5/锌浴界面产生Fe Zn10(d)相;另一种是Zn通过Fe_2Al_5晶界向钢基体扩散,直接在Fe_2Al_5/钢基体界面产生d相,并引起Fe_2Al_5的迸发失稳.
Under the condition of galvanization at 450 ℃, the mass fraction of Al is 0.2% in the zinc bath, the structure of the coating is observed by SEM, the micro-composition of the phase is quantitatively analyzed by EDS, and the cross-section elements The thermodynamic parameters of each binary Fe-Al, Fe-Zn and ternary Fe 2 Al_5Znx (h) intermetallic compounds (IMC) in coatings were calculated by Miedema model and Toop model. With the extension of galvanizing time, The results show that Fe-Al IMC has more stable thermodynamic properties than Fe-Zn IMC, and the interface between the steel substrate and the zinc bath gives priority to the continuous Fe 2 Al 5 intermetallic Compound inhibition layer, but inhibited Fe-Zn reaction, but with the extension of galvanizing time, the instability of Fe 2 Al 5 lost the inhibition of Fe-Zn reaction and formed Fe Zn 10 (d) phase.The instability mechanism of Fe 2 Al 5 inhibition layer was two Species: one is the partial depletion of Al at the interface of Fe 2 Al 5 / zinc bath, which leads to the erosion of Fe 2 Al 5 by Zn and the formation of Fe 2 Al 5 Znx, which leads to the decrease of the thermodynamic stability of the system, resulting in the decomposition of Fe 2 Al 5 by Zn and the formation of Fe Zn10 (d) phase; the other One is the diffusion of Zn through the Fe 2 Al 5 grain boundary to the steel matrix, which directly produces the d phase at the Fe 2 Al 5 / steel matrix interface and causes the burst failure of Fe 2 Al 5.