Investigation of Superplastic Behavior in FSP 5083 Aluminum Alloy

摘要

Continuously-cast AA5083 in the form of as-cast billets 15 mm in thickness condition was subjected to friction stir processing (FSP) by five overlapping passes. The FSP utilized a tool having a pin approximately 5 mm in length, so that the process zone had a depth that was approximately one-third of the billet thickness. The solidification microstructure of the as-cast material included grains that were approximately 60 m in size as well as non- equilibrium distributions of the Al8Mg5 and Al6Mn phases. Within the process zone the grains were reduced to approximately 1.0 m in size and the distribution of second-phase particles had become homogeneous. Microhardness traverses through the process zone into base material revealed that the hardness was increased from 80 to 120 kg mm-2 for the AA5083 material while the hardness was increased from 80 to '180 kg mm-2 for AA5083 + 0.5 wt. pct. Cu. The elevated temperature tensile properties were evaluated by tension testing of coupons that had been sectioned from the process zones of the billets. For the AA5083 material superplastic ductility of 1245% elongation to failure was obtained at a nominal strain rate of 10-1 s-1 and superplastic response was observed in tension tests conducted at strain rates of 10-2 s-1 and 3 10-1 s-1. The stress - strain curves exhibited hardening, and the test coupons appeared to deform with minimal cavitation and failure took place by flow localization. Lower ductility of 143% elongation to failure was observed in the AA5083 + Cu material tested 10-2 s-1. Failure occurred by cavitation growth and linkage with minimal flow localization in the material with a Cu addition.