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Nathalie Gouret (V.2)
Abstract
A contribution to the study of the origin of porosities in electron beam welded joints in Ti6Al4V
Nathalie Gouret - 19 november 2001.
The manufacturing of blanks using the electron beam welding technology is the most serious alternative to die forging. The mechanical properties of TA6V joints are approximately equal to those of the base material. The only cause of a decrease of the fatigue life of a welded structure can be the presence of porosities in the fusion zone. To apply this technology to class 1 components on civil aircrafts, it is needed to know how to avoid the formation of porosities. The main goal of the thesis is to achieve the understanding of the formation of pores in the fusion zone. It demonstrates and quantifies the influence of chemical surface treatments and machining on the quality of the welded joints. The role of various chemical elements have been experimentally and theoretically proved. The use of chemical analysis equipment such as SIMS and ERDA allow the author to reach the accurate chemical composition of the material after various treatments. A model based on Rayleigh Plesset's equation and laws of thermodynamics have been established to compute the composition of the gaz inside the pores and the dimension of the defects .
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