Cracking During Forging of Extruded Aluminum Alloy Bar Stock Material

During the preproduction stages of forging, an initial batch of 50 mm (2 in.) diam Al-4Cu alloy (L77) extruded bar stock material was found to be cracking randomly. Failure analysis was conducted to determine the metallurgical factors underlying the phenomenon. Microexamination of sections across the defects revealed intergranular cracks tracing a path of round, segregated particles and oxide film discontinuities. The segregated particles were rich in copper It was concluded that the cracking was the result of segregations occurring in poor-quality raw material. The source of segregation was suspected to be the use of improperly made master alloys. Use of improved melting techniques and proper master alloys was recommended.