Experimental study of structure formation in binary Al–Cu alloys at different cooling rates

✍ Scribed by D. Eskin; Q. Du; D. Ruvalcaba; L. Katgerman

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 465 KB
• Volume: 405
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2005.05.105

✦ Synopsis

A series of casting experiments was performed with binary Al-Cu alloys with varying cooling rates, cooling conditions and copper concentration. The quantitative relationships between the cooling rate (V c ) and composition, on one hand and the dendrite arm spacing (DAS) and grain size (D gr ) on the other hand, are clarified in the form of coefficients in equation DAS (D gr ) = AV -n c , where coefficient A is shown to strongly depend on the copper concentration. Increasing the amount of copper in the alloy causes refinement of both dendrite arm spacing and grain size. The amount of non-equilibrium eutectic depends on the cooling rate in a more complex manner with initial increase in the range of slow cooling (<1 K/s) and then gradual decrease in the range of 1-10 K/s. Some models of microsegregation are tested but fail to reproduce the experimentally observed dependences. The reasons for such a behaviour are discussed in terms of dendrite arm coarsening, eutectic reaction undercooling, structure refinement and homogenization upon cooling in the solid state.