Microstructure evolution and nano-phases strengthening of Al-5%Cu alloy by adding trace AlSiTiCrNiCu high entropy alloy

In the present work, AlSiTiCrNiCu high entropy alloy (HEA) has been used in as-cast Al-5wt%Cu alloy to investigate the effect of HEA addition level (0.3 wt% and 0.6 wt%) on the microstructure and mechanical performance. The results revealed that the addition of HEA has a distinct influence on the size and morphology of primary ?-Al and second phases in the cast Al-5wt%Cu alloy. When 0.3 wt% and 0.6 wt% HEA was added to Al5wt.%Cu alloy, the primary ?-Al dendrites was obviously refined and the mean size of ?-Al grains was significantly reduced from 372.5 ?m to 183.4 ?m and 156.3 ?m, respectively. Meanwhile, the size and morphology of 0-Al2Cu phases distributing inter-dendritic zone occurred to obvious change with increase of HEA addition concentration. In addition, the 0-Al2Cu phases disappeared and eutectic Al3CuNi phases precipitated after adding the HEA in Al-5wt%Cu alloy. Compared with 0-Al2Cu phases, the width was decreased and the continuity of Al3CuNi was improved when HEA was added to Al-5wt%Cu alloy. Moreover, it was found by TEM that some novel nano-particles precipitated from Al-5wt%Cu alloy with the addition of HEA in solidification, which uniformly distributed in the ?-Al matrix. The yield strength, ultimate tensile strength and elongation of Al-5wt%Cu alloy with 0.6 wt.% HEA addition were significantly increased by 19.7%, 20.1% and 92.3%, respectively. The improvement of mechanical properties was attributed to change of morphology and decreasing size of ?-Al and Al3CuNi phases. In addition, a new plate-like structure precipitated which morphology is similar to 0 phase and multi-elements nano-particles formed, which strengthened the Al-5wt%Cu alloy.

Automated summary

In this study, the addition of AlSiTiCrNiCu high entropy alloy (HEA) to the as-cast Al-5wt%Cu alloy significantly refined the primary ?-Al dendrites, reduced the grain size of ?-Al, and induced changes in the morphology and size of the 0-Al2Cu phases. The addition of HEA also led to the precipitation of novel nano-particles and improved the mechanical properties of the Al-5wt%Cu alloy.