Improvement of yield strength of LM24 alloy

• Significant improvement of yield strength of LM24 alloy was obtained.
• Primary Si phase disappeared after addition of in situ Al2O3 particles into LM24 alloy.
• The mechanical properties of Al2O3/LM24 still possess stability after remelting.

In this study, Al2O3 particles were employed to improve the microstructure of LM24 and therefore, to increase the yield strength and tensile strength of this kind of alloy. In situ Al2O3 particles were obtained by direct reaction between oxygen and Al melt at 750–800 °C. Microstructure examination shows that the size of in situ formed Al2O3 particles was about 1–2 μm, and interestingly, with addition of in situ Al2O3 particles, the coarse primary Si phase was disappeared completely. More important, the yield strength and the tensile strength of Al2O3/LM24 are increased by 52 MPa, 16 MPa than that of LM24 alloy with 0.1% Sb addition. The value of 181 MPa and 315 MPa is for yield strength and tensile strength of Al2O3/LM24 respectively. Besides, the yield strength and tensile strength are 180 MPa and 314 MPa respectively for Al2O3/LM24 alloy after remelting and casting. This verifies that the improvement of mechanical properties of such kind of material possesses stability and reliability.