摘要
Cast aluminium alloys are important structural materials but their performances are not optimised due to the lack of appropriate grain refiners. In this study, the effect of the addition of a novel Nb-based grain refiner on the microstructural features and mechanical behaviour of the LM6 alloy (A413) is studied. Specifically, the effect of Nb-B inoculation is assessed over a great range of cooling rates (2-100 degrees C/s). It is found that Nb-based compounds (i.e., NbB2 and Al3Nb) are potent heterogeneous nucleation sites for aluminium and this leads to a significant refinement of the microstructural features. The refinement is not hindered by the formation of silicides, as it happens when using Al-Ti-B master alloys, because niobium silicides form at much higher temperature. It is concluded that the Al-2Nb-2B master alloy is a very effective refiner especially at slow cooling rate and the refinement of the grain size leads to improved performances (homogeneous fine grain structure, mechanical properties and porosity).
- 出版日期2015-3-25