TY - JOUR A1 - Coniglio, N. A1 - Cross, Carl Edward A1 - Dörfel, Ilona A1 - Österle, Werner T1 - Phase formation in 6060/4043 aluminium weld solidification JF - Materials science and engineering A N2 - Weld metal microstructure for alloy 6060 aluminum welds, made using the gas-tungsten arc process and alloy 4043 filler metal, has been characterized using optical metallography, EPMA microprobe analysis, SEM/EBSD and STEM/EDX electron microscopy, and single-sensor differential thermal analysis (SS-DTA). In addition, alloy 6060 castings were solidified at variable cooling rates approaching that of welding, to provide a reference for comparison with weld microstructure. It was found that a major change in cast microstructure occurs at cooling rates higher than 27 K/s resulting in a structure similar to that observed in weld metal. Rapid cooling is believed to favor low temperature solidification reactions that normally would be achieved only at higher silicon content. Accordingly, additions of 4043 filler metal that increase the weld metal silicon content have only limited affect on weld solidification range and microstructure. This has direct implications regarding how 4043 filler additions improve weldability and weld quality. KW - 6060 aluminium KW - GTA weld KW - Weld metal microstructure KW - Cooling rate KW - Scanning TEM KW - Thermal analysis PY - 2009 DO - https://doi.org/10.1016/j.msea.2009.03.087 SN - 0921-5093 SN - 1873-4936 VL - 517 IS - 1-2 SP - 321 EP - 327 PB - Elsevier CY - Amsterdam AN - OPUS4-20625 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Coniglio, N. A1 - Cross, Carl Edward T1 - Mechanisms for solidification crack initiation and growth in aluminium welding JF - Metallurgical and materials transactions A N2 - 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. KW - 6060 aluminium KW - Weld solidification cracking KW - Crack initiation/growth mechanisms KW - Transverse strain rate KW - Porosity formation PY - 2009 DO - https://doi.org/10.1007/s11661-009-9964-4 SN - 1073-5623 SN - 1543-1940 VL - 40 IS - 11 SP - 2718 EP - 2728 PB - The Minerals, Metals and Materials Society CY - Warrendale AN - OPUS4-20627 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -