Evaluation of susceptibility to hot cracking of WE43 magnesium alloy welds in transvarestraint test

In castings of magnesium alloys defects or inconsistencies often appear (like casting misrun, porosities and cracks) particularly in the huge dimensional castings. Such defects are mended with the use of padding and welding. The welding techniques can be applied by using weld material consisting of magnesium alloy, as well as for regeneration of alloys after excessive wear. Nevertheless, the number of the repaired castings, which were permitted for use, is not satisfactory for a profitable production. The main reasons for wear are the cracks appearing during welding in brittleness high-temperature range. This work in combination with industrial tests of casting welding shows that the causes of high-temperature brittleness are the partial tears of the structure and the hot cracks of both the castings and the welded and padded joints. Such phenomena should be treated as irreversible failures caused by the process of crystallisation that is in the area of co-existence of the solid and liquid structural constituent. The assessment of the resistance to hot fractures was conducted on the basis of the transvarestriant trial. The transvarestriant trial consists of changing the strain during welding. It was stated that the range of the high-temperature brittleness is very broad, which significantly limits the application of the welding techniques to join or mend the elements made of alloy WE43. The brittleness is caused mainly by metallurgical factors, i.e., precipitation of inter-metal phases from the solid solution.