硅含量对Al-Si-Cu相变储能材料腐蚀性的影响

Effect of Si Content on Liquid Corrosivity of Al-Si-Cu Energy Storage Materials

合金液的腐蚀性较大是铝合金作为相变储能材料应用的主要瓶颈。鉴于材料成分是影响其液态腐蚀性的重要因素之一,本工作设计了304不锈钢在Al-x Si-10Cu(6≤x≤15)合金液中的腐蚀试验,以期探讨Si含量对该材料液态腐蚀性的影响。采用电子探针和XRD对腐蚀产物的形貌、元素分布和相组成进行了分析,并对腐蚀反应进行了动力学和热力学分析。结果表明:随着Si含量的增加,腐蚀层厚度和腐蚀产物的生长系数先降低后增加,而腐蚀产物的扩散激活能却先增加后降低,但都在Si含量为9%时达到极值。Si含量在6%～9%,当腐蚀时间较短时,腐蚀层由Al95Fe4Cr相和Fe2Al5相组成,Si填充Fe2Al5相的空位,阻碍了元素扩散;当腐蚀时间较长时,腐蚀层由Al95Fe4Cr相、FexSiyAlz相和FeAl相组成,FexSiyAlz相不仅生长速率低还可阻挡元素的扩散,且FeAl相的生成焓大于Fe2Al5相,从而降低腐蚀层的厚度。Si含量在9%～15%内时,腐蚀层厚度增加的具体原因有待进一步研究。

High liquid corrosivity has long became the obstacle to the application of Al alloys as phase-change energy-storage materials.It has been common knowledge that the composition of energy storage material is one of the important factors that affect its liquid corrosivity.Thereby,in this work,a corrosion test scheme of 304 stainless steel in liquid Al-x Si-10Cu (6≤ x ≤15) alloys was conducted,so as to investigate the effect of Si element content on liquid corrosivity.We characterized the morphology,element distribution and phase composition of the corrosion products by means of electron probe and XRD,and also carried out kinetic and thermodynamic analyses for the corrosion reaction.The results showed that with the increase of Si content,both the corrosion layer thickness and the growth coefficient of corrosion products exhibit biphasic (decrease→ increase) change,while the diffusion activation energy of corrosion products displays an opposite variation,and all of them reach the minimum or maximum value at the Si content of 9%.When the Si content is in the range of 6%~9%,a short-duration corrosion leads to a corrosion layer mainly composed of Al95Fe4Cr phase and Fe2Al5 phase,the vacancies of the latter of which can be filled by Si atoms so that the corrosive elements diffusion can be attenuated.But a long-duration corrosion leads to a corrosion layer mainly composed of Al95Fe4Cr phase,FexSiyAlz phase and FeAl phase.The FexSiyAlz phase grows quite slowly and can prevent element diffusion.Moreover,the formation enthalpy of FeAl phase is larger than that of Fe2Al5 phase,so the corrosion thickness can be reduced.When the Si content ranges in 9% to 15%,the specific reason for the corrosion thickness increment with the addition Si element remains unclear and further study is needed.