Papers by Keyword: Eutectic Reaction

Abstract: The refining effects of La-Ce binary alloy on the primary α phase in semisolid A356 alloy prepared by electromagnetically stirred were researched, in which the refinement mechanism of the binary alloy on primary α phase were emphatically approached. The different amount of La-Ce was added into A356 melt, the melt was poured at 620°C and slightly electromagnetically stirred for 15s with an electromagnetic stirrer which was controlled by frequency conversion, then it was isothermally held at 615°C for 10min. The shape and size of primary α phase were measured, and the distribution of La and Ce was researched by SEM and EDS. The results indicated that the RE elements were easy to uniformly distribute around the primary α phase under electromagnetic stirring, and had the obvious refining effect on primary α phase in semisolid A356 alloy, in which there was the finer primary α phase with particle-like in the melt. The refinement mechanism of La-Ce binary alloy under electromagnetic stirring was concerned with the eutectic reaction between RE elements and Al in the melt, in which the α-Al phase resulted from the Al-RE eutectic reaction could serve as the nucleating site of the primary α phase during solidification of A356 alloy. The other reactant from the Al-RE eutectic reaction, Al₁₁Ce₃, was also directly used as nucleation of α phase during the solidification.

Abstract: Semisolid A356 alloy was prepared by low superheat pouring. The effects of La as a kind of refinement on the size and morphology of the primary phase in semisolid A356 alloy were researched. The results indicated that semisolid A356 alloy contained certain La addition with particle-like and rosette-like primary phase could be prepared by low superheat pouring. The size and morphology of primary phase in A356 alloy are markedly improved by the suitable addition of La. The refining mechanism of La on the size and morphology of the primary phase in semisolid A356 alloy were concerned with the eutectic reaction induced by La in the alloy.

Abstract: Semisolid A356 alloy, which is grain-refined by Pr, was prepared by low superheat pouring. The effects of grain-refined by Pr on the morphology and the grain size of the primary α-Al in semisolid A356 alloy are researched. The results indicate that semisolid A356 alloy with particle-like and rosette-like primary α-Al can be prepared by low superheat pouring from liquid A356 alloy grain-refined by Pr. The grain size and particle morphology of primary α-Al in A356 alloy are markedly improved by 0.3wt% Pr. The refining mechanism of Pr on the morphology and the grain size of the primary α-Al in semisolid A356 alloy were delved.

Abstract: Al2O3-30vol%ZrO2 nano-submicron structured ceramics has been obtained from high-temperature melts produced by SHS metallurgical process, SEM images show that the multiphase ceramics is mainly composed of Al2O3 matrix eutecticums in which ZrO2 fibers are up to nano-submicron scale, resulting in formation of intra-granular structures. Vickers hardness test indicates that critical value of indentation load which induces median crack to extend is 30kg, and morphologies of Vickers indentation indicate that the ceramics is performed with high fracture toughness and high plasticity. Meanwhile, SEM images show that crack extension is mainly controlled by fiber eutecticums of intra-granular structures with nano–submicron ZrO2 phases, XRD demonstrates that toughening mechanism of stress induced ZrO2 phase transformation is considered weak through comparing volume fraction of m-ZrO2 before fracture to the one after fracture, and toughening behavior of multiphase ceramics is mainly controlled by nano-submicron phase toughening mechanism.