| 摘要 |
A method wherein an optionally partially worked rough blank casting is provided then (1) the oxide layer on the castings is removed and means are implemented to prevent it being reformed, (2) a heat treatment is carried out in a furnace containing a non-oxidising atmosphere in order to homogenise and redissolve precipitates comprising alloying elements present in the aluminium matrix, (3) the homogenising heat treatment is continued under conditions enabling most of the hydrogen in the castings to be extracted until the hydrogen content is reduced to less than 0.05 ppm and preferably less than 0.03 ppm, and (4) said castings are worked in such a way that the thickness or cross-section thereof is reduced by at least 10 %, under such conditions that any residual pores remaining after the precipitates have been redissolved and the gas removed may be filled. Said method advantageously includes a further step (5) of selecting worked castings by means of a non-destructive testing method whereby residual flaws with a size exceeding a predetermined threshold may be detected, the flaw density may be determined and castings having a flaw density higher than a predetermined threshold may be discarded. |
