{'fraction_non_alphanumeric': 0.011192589733693555, 'fraction_numerical': 0.00887688151292937, 'mean_word_length': 5.447761194029851, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Microstructure and its stability at elevated temperature in friction stir seam welded dissimilar joints of 5083 and 6061 aluminium alloy plates

Friction stir welding has been taken as an important welding technique for metals such as aluminium alloys and there are an increasing number and an extensive range of fundamental studies and applications to materials used in-service. As illustrated in many papers and technical materials, joints obtained by this method have minute crystal grain structure as the common characteristic, and the precipitation structure and solidification structure specific to each material added a diversity and difference to the microstructure of the weld. These should be studied as the non-constant structure formation process which progresses in complex plastic deformation mode. Incidentally, there is no guarantee that the microstructure obtained in friction stir welding is always in a stable state. For example, as reported with friction stir welded 5083 aluminium alloy joints, the region with minute crystal grains which is formed at the friction stir welded zone of this alloy is unstable in high temperature environment, and so, when it is kept in the over 773 K temperature region, preferential crystal grains start becoming coarser from the region which was in contact with the shoulder and part of the region in the stirred zone. In other words, this means that a cause for the microstructure at the friction stir welded section becoming coarser at high temperature during the joining process has been introduced as the crystal grains becoming finer. Microstructures of materials are in the present state by considering the process history and thermal hysteresis which each material has received. It includes the information on microstructure such as annealing, which will have an influence during the change of microstructure when the environment changes. Accordingly, grasping the information on microstructure existing potentially also leads to the securing of the reliability of microstructure. In the joining of dissimilar materials, a mixture of processes occurring at the stirred zone are expected to generate even more complex microstructure. In other words, the formation process, in high temperature environment, of microstructure at the joint welded with the mechanical mixing or mutual diffusion of materials with different chemical potentials leads to the emergence of the ‘alloying’ region Microstructure and its stability at elevated temperature in friction stir seam welded dissimilar joints of 5083 and 6061 aluminium alloy plates