Mechanisms for Solidification Crack Initiation and Growth in Aluminum Welding
Mechanisms for Solidification Crack Initiation and Growth in Aluminum Welding
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DOI：
10.1007/s11661-009-9964-4
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发表时间：
2009-11-01
影响因子：
2.8
通讯作者：
Cross, C. E.
中科院分区：
文献类型：
--
作者：
Coniglio, N.;Cross, C. E.
提出了6060铝合金焊接接头凝固裂纹萌生和扩展的机理。使用Rappaz-Drezet-Gremaud(RDG)模型对枝晶间液体压降进行的计算表明，除非氢含量升高，否则不太可能发生空化作为液体破裂机制。取而代之的是，基于孔隙率的裂纹萌生模型是基于孔洞稳定性标准，假设气孔从先前存在的核扩展而来。裂纹萌生是在共格枝晶区域内形成稳定的气孔时发生的，这取决于氢的含量。裂纹萌生后，用质量平衡法模拟裂纹扩展，由局部应变率条件控制。根据局部应变率测量和简化的应变率分配模型，确定了16%4043填充量的焊缝凝固裂纹扩展所需的临界晶界液体变形率。组合模型表明，氢和应变率分别控制裂纹的萌生和扩展。提出了一个假设的氢应变速率图，从概念上定义了裂纹和孔洞所需的组合条件。
In the present work, mechanisms are proposed for solidification crack initiation and growth in aluminum alloy 6060 arc welds. Calculations for an interdendritic liquid pressure drop, made using the Rappaz-Drezet-Gremaud (RDG) model, demonstrate that cavitation as a liquid fracture mechanism is not likely to occur except at elevated levels of hydrogen content. Instead, a porosity-based crack initiation model has been developed based upon pore stability criteria, assuming that gas pores expand from pre-existing nuclei. Crack initiation is taken to occur when stable pores form within the coherent dendrite region, depending upon hydrogen content. Following initiation, crack growth is modeled using a mass balance approach, controlled by local strain rate conditions. The critical grain boundary liquid deformation rate needed for solidification crack growth has been determined for a weld made with a 16 pct 4043 filler addition, based upon the local strain rate measurement and a simplified strain rate partitioning model. Combined models show that hydrogen and strain rate control crack initiation and growth, respectively. A hypothetical hydrogen strain rate map is presented, defining conceptually the combined conditions needed for cracking and porosity.