Effects of lanthanum addition on microstructure and mechanical properties of as-cast pure copper

As-cast Cu-La alloys with La contents in the range of 0–0.32 wt.% were fabricated by vacuum melting method. The effects of La on microstructure and mechanical properties of as-cast pure copper were investigated using optical microscopy (OM), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and tensile test. The results showed that La had obvious effects on the solidification microstructure and the grain refinement of as-cast pure copper. With the increase of La content, the ultimate tensile strength, the yield strength and the microhardness increased gradually, but the elongation increased first and then decreased while La content exceeded 0.089 wt.%. The improvement of mechanical properties was attributed to the effect of grain refinement strengthening, solid solution strengthening, second phase strengthening and purifying. However, excessive adding La would deteriorate the elongation owing to the excessive Cu6La phases.

Graphical AbstractThe addition of trace La can lead to the formation of the columnar grain, while the addition of much La can provoke a transition from columnar grain structure to equiaxed grain structureFigure optionsDownload full-size imageDownload as PowerPoint slide