Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2014
Thesis Language: Turkish
Student: Arif Uzun
Supervisor: MEHMET TÜRKER
Abstract:In this study, foamable metallic preform materials were produced and joined by friction stir welding before foaming. For this, 7% Si, 1% TiH2 (foaming agent) and B4C at various rates powders were added to the Al powders and then were mixed properly. Mixed powders were compacted at 400 MPa and extruded and rolled at 550oC so that precursor material was obtained. These precursor materials were joined by friction stir welding (FSW) at different rotation speeds (1250, 1600 ve 2000 rev/min) and welding speeds (40, 63, 80 mm/min). Then welded samples were foamed at temperatures between 690oC and 710oC to produce closed cell metallic foams. As a result of experimental studies, the expansion rate of B4C reinforced preform materials has been found to be lower than AlSi7 foams. Expansion values were increased with increase in foaming temperature. Pore size was increased with foaming temperature and the amount of B4C in the samples but the number of pores was decreased. The maximum tensile strength for welded 6% reinforced and unreinforced materials were obtained in 1600 rev/min rotation speed and 40 mm/min welding speed. In contrast to the base material of strength values of welded materials have been found to be lower. In a result of free foaming, the welding zone compared to the base material was showed weaker expansion behavior. However, a significant welding region or welding track in their structure with the foaming process in the mold was unwatched. The bending strength of 6% reinforced and unreinforced foam materials was increased with increase relative density. The bending strength was increased with B4C addition on the other hand was decreased by FSW.