E2EM’s prediction of LaB6 as nucleation substrate for primary Mn-rich phase in Al-Si-Cu-Mn heat-resistant alloy and its refining effect
(Jiangsu Key Laboratory of Advanced Metallic Materials, School of Materials Science and Engineering, Southeast University, Nanjing 211189, China)
Abstract: Edge-to-edge matching (E2EM) model was used to predict the potency of LaB6 as the heterogeneous nucleation substrate for primary Al13Mn4Si8 phase formed during the solidification of Al-Si-Cu-Mn heat-resistant alloy. There are five pairs of orientation relationships (ORs) between LaB6 and Al13Mn4Si8 phases which meet the criteria of E2EM model. One pair of plane ORs ((110)LaB6//(110)Al13Mn4Si8) are demonstrated by TEM observation. This strongly indicates that the LaB6 phase can act as the heterogeneous nucleation substrate for the primary Al13Mn4Si8 phase. 1.0 wt.% of Al-2La-1B master alloy was also added into Al-12Si-4Cu-2Mn alloy to evaluate the refining effect by microstructure observation and tensile test. Experimental results show that addition of Al-2La-1B master alloy can significantly refine the primary Al13Mn4Si8 phase, supporting the prediction accuracy of E2EM model. However, such refinement of primary Al13Mn4Si8 phase does not lead to an improvement in strength. This is due to the larger difference in elastic modulus between the finally formed Al13Mn4Si8 phase and aluminum matrix than that of Al15Mn3Si2 phase.
Key words: edge-to-edge model; Al13Mn4Si8 phase; LaB6 phase; heat-resistant aluminum alloy; microstructure; mechanical property