Microstructure and Hardness Properties of Beryllium Bronze with Lanthanum Addition Fabricated by Rheological Squeeze Casting Process

Rheological squeeze casting is a novel metal forming process, which can realize the integration of preparation and forming, and achieve the effect of energy saving and emission reduction. In order to investigate the application of rheological squeeze casting process on beryllium bronze alloy and to verify the improvement in beryllium bronze properties under the condition of rare-earth lanthanum addition, in this paper, a beryllium bronze workpiece with rare-earth La (0-0.30 wt%) was formed by rheological squeeze casting. The results revealed that with the increase in La content, the grain size gradually refined and became spherical, and the hardness increased from 158 to 213 HBW (by 34.8%). The rheological squeeze casting process greatly improves the nucleation rate, resulting in grain refinement. La and its compounds result in constitutional undercooling and heterogeneous nucleation, and the pressure applied in the rheological squeeze casting process affects solute diffusion and deepens the degree of undercooling. The dual effects of these aspects enhance grain refinement and result in an increase in hardness.