EXCESSIVE GRAIN-GROWTH IN FORGED ALUMINUM-BASE COMPRESSOR BLADES

This paper describes experiments carried out to ascertain the cause of excessive grain-growth in 2618 aluminium-base compressor blades. The specimens were cold-rolled to various strain levels, soaked at the forging temperature and then subsequently heat treated, to simulate the hotforging operation used in the manufacture of the blades. From the evolution of the grain structure at various stages of the above process, the critical process-parameters responsible for the coarse-grained structure of the blades have been identified. The results show that: (i) an insufficient amount of strain sustained during forging; (ii) too high a solution-treatment temperature; and (iii) excessively rapid quenching of the forgings coupled with slow heating during the subsequent solution treatment; are plausible causes for the coarse-grained structure observed in the blades. The results are discussed in relation to the industrial practice used in the manufacture of the blades. © 1990.