钎焊式空冷系统用嵌入式冷轧铝-钢复合带材的开发

通过＂表面处理＋冷轧复合＋退火处理＂三步法,即先采用钢丝刷对4 mm 08Al钢（/%：0.01C,0.018Al）和0.23 mm 4A60铝带表面进行处理,然后在前张力30 kN下利用高精度Φ420 mm四辊轧机对铝-钢进行60%的单道次冷轧复合,并于罩式退火炉进行520℃24 h的退火处理,开发出了极薄复层（80~90μm）冷轧4A60铝/08Al钢1.7 mm复合带材。复合带材中08Al钢的组织为平均晶粒尺寸15μm的等轴铁素体,抗拉强度≥320MPa,伸长率≥28%,弯曲性能也符合指标要求。复合带材在（600±10）℃钎焊后铝钢界面未发现金属间化合物,铝钢界面未发现分层现象。

铝(4A60)-钢(08Al)复合带材界面化合物形成及结合性能

采用金相显微镜、扫描电镜和X射线衍射仪，研究电站空冷用铝（4A60）？钢（08Al）复合带材在不同模拟钎焊工艺下界面化合物的生长特性。通过界面剥离实验，分析不同钎焊条件下复合带材结合性能的变化规律。结果表明：在钎焊保温时间20 min内，铝（4A60）？钢（08Al）复合带材生成界面金属间化合物（IMC）的临界温度范围为605~615℃，界面相主要成分为Fe 2 Al 5。界面金属间化合物厚度随保温时间的增长满足抛物线规律，在615℃时，生长常数k为0.69＆#215;10？12 m2/s。界面金属间化合物厚度在12μm以下时，复合带材仍保持良好的界面结合强度（大于45 MPa）。随着金属间化合物厚度继续增加，界面结合强度显著下降，当金属间化合物厚度为25~43μm时，结合强度降至10~20 MPa；当金属间化合物厚度为54~68μm时，界面结合强度只有5~10 MPa。

Formation mechanism and control of aluminum layer thickness fluctuation in embedded aluminum-steel composite sheet produced by cold roll bonding process

The influences of rolling reduction and aluminum sheet initial thickness(AIT)on the thickness fluctuation of aluminum layer(TFA)of embedded aluminum?steel composite sheet produced by cold roll bonding were investigated,the formation mechanism of TFA was analyzed and method to improve the thickness uniformity of the aluminum layer was proposed.The results showed that when the reduction increased,TFA increased gradually.When the reduction was lower than40%,AIT had negligible effect on the TFA,while TFA increased with the decrease of AIT when the reduction was higher than40%.The non-uniformities of the steel surface deformation and the interfacial bonding extent caused by the work-hardened steel surface layer,were the main reasons for the formation of TFA.Adopting an appropriate surface treatment can help to decrease the hardening extent of the steel surface for improving the deformation uniformity during cold roll bonding process,which effectively improved the aluminum thickness uniformity of the embedded aluminum/steel composite sheets.

冷轧复合铝-铝-钢界面金属间化合物的生长行为

对冷轧复合4343铝/4A60铝/08Al钢三层复合带材进行不同温度和时间的退火,借助金相显微镜、扫描电镜和EDAX能谱仪以及X射线衍射仪对复合界面结合区进行组织观察、元素成分线扫描分析和EDS能谱分析及XRD物相分析,研究复合界面金属间化合物的生长行为。结果表明:当退火温度较高时,4343中含量较高的Si向4A60中进行了较大程度的扩散;铝-钢复合界面在600℃保持1 h退火时有金属间化合物产生;随着退火温度的升高和退火时间的延长,复合界面金属间化合物由一层增加至三层,化合物主要由Fe4Al13和Fe2Al5组成;铝-钢复合界面金属间化合物的生长由扩散控制,其增厚符合抛物线规律,界面金属间化合物的生长激活能为14.4 k J/mol。