Variation in the microstructure and mechanical properties of permanent mold cast Al-3Li-2Mg-0.1Zr alloy with Zn addition

In this research, microstructure characterization, phase analysis and tensile tests were performed to investigate the influence of Zn content upon permanent mold cast Al-3Li-2Mg-0.1Zr alloy. Results showed that the most significant grain refinement was caused by 1 wt% Zn as constitutional undercooling was increased with Zn addition and decreased with the formation of (Al, Zn)(49)Mg-32 phases. To dissolve second phases in as-cast alloys, including Al3Li, Al12Mg17, Al2MgLi, AlLi and (Al, Zn)(49)Mg-32, three-stage solution treatment (500 degrees C/10 h + 535 degrees C/10 h + 560 degrees C/20 h) was designed. After quenching and artificial aging for 8 h at 175 degrees C, Al-3Li-2Mg-1Zn-0.1Zr alloy presented the optimum comprehensive mechanical properties. The elongation, yield strength and ultimate tensile strength reached 6.9%, 221 MPa and 351 MPa, respectively. The performance improvement with Zn addition was mainly attributed to grain refinement and solution strengthening, while the composition of precipitates was almost unaffected.

Automated summary

The study revealed that the addition of Zn can significantly refine the grain and enhance the strength of the alloy; a specific solution treatment process can effectively remove second phases from the alloy; the addition of Zn can improve the comprehensive mechanical properties of the alloy.