| Title |
Effect of La Addition and Heat Treatment on the Microstructure and Mechanical Properties of Al?Si?Cu Alloys |
| Authors |
허우로(Uro Heo) ; 이재원(Jaewon Lee) ; 배영훈(Young Hoon Bae) ; 김경훈(Kyeonghun Kim) ; 양해웅(Haewoong Yang) |
| DOI |
https://doi.org/10.3365/KJMM.2026.64.1.49 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Lanthanum; Heat treatment; Aluminum alloy; Mechanical Properties; Die Casting |
| Abstract |
This study investigates the effects of minor lanthanum (La) addition and heat treatment on the microstructure and
mechanical properties of Al?10%Si?2%Cu alloys produced by high-pressure die casting. Alloys containing 0 wt.% and
0.5 wt.% La were solution-treated at 500 oC and aged at 160 oC for 0 and 6 hours. Microstructural observations showed that
the combined application of La addition and aging led to significant grain refinement of α-Al and a more homogeneous
distribution of eutectic Si phases. SEM/EDS and XRD analyses revealed the formation of polygonal and needle-like La?Cu
intermetallic compounds, including the thermally stable LaCu2Al4Si1 phase, which effectively inhibited grain coarsening during
aging. DSC analysis showed that the contact angle between α-Al and Si phases decreased from 21.3o to 14.4o after aging,
indicating improved interfacial wettability and reduced nucleation energy. These changes promoted the formation of fine and
uniform microstructures. As a result, the alloy containing 0.5 wt.% La and aged for 6 hours exhibited the highest average
microhardness of 124 HV. The improved mechanical performance is attributed to the combined effects of grain refinement,
suppression of interfacial energy, and uniform precipitation behavior. These findings emphasize the critical role of La in
stabilizing the microstructure and enhancing hardness through controlled phase distribution and interfacial modification in diecast
aluminum alloys. |