Effect of Cu content on mechanical strength of improved 5052 Al-Mg alloys Cu-added by electron beam process

The optimum Cu content in the improved 5052 alloy with Cu addition by the e lectron beam welding process was investigated by the measurement of tensile tests to determine the mechanical strength of the improved 5052 alloys and the interface between the substrate and the improved area of the alloys. T he X-ray diffraction or EDAX analysis of the precipitates, the observation of scanning electron micrographs of the samples with or without improved tr eatment and the fracture surface after tensile tests were also performed. The main results obtained are summarized as follows: (1) The grain size of Al (or) phase in the improved 5052 alloys was below 10 mu m in diameter. Th e Al (alpha) + Al2Cu eutectic structure crystallized around the Al(alpha) p hase, and its surface area ratio of the eutectic structure increased with i ncreasing Cu content in the improved alloys. However, the surface area rati o of the eutectic structure was almost constant at the Cu content higher th an 15 mass%. On the contrary, the surface area ratio of the large size of t he Al2Cu intermetallic compound increased with increasing Cu addition at th e Cu content higher than 15 mass%. (2) The Vickers hardness of the improved 5052 alloys increased with increasing Cu content in the 5052 alloy. The me chanical properties such as U.T.S. of the improved alloys increased with in creasing Cu addition at the Cu content below 10 mass%. The values of U.T.S. were almost constant at the Cu content from 10 to 15 mass%. However, the m echanical strength of the improved 5052 alloys was reduced to the Cu conten t higher than 15 mass%. The mechanical strength of the in interface between the substrate and the improved area was also reduced with increasing Cu co ntent in the range higher than 15 mass%. (3) The fracture cracking initiati on is observed around the large size of Al2Cu intermetallic compound, and t hus the deterioration in mechanical strength for the improved 5052 alloy an d interface between the substrate and the improved area of the samples was caused mainly by the increased large size of the Al2Cu intermetallic compou nd. From the experimental data, the optimum Cu content in the improved 5052 alloy was decided to be 10 mass%.