Effect of Directional Solidification Rate on Preferred Orientation, Microstructure and Magnetostriction of (Tb_(0.3)Dy_(0.7))Fe_(1.95) Alloys

摘要

The effect of solidification rate on the preferred orientation, microstructure and magnetostriction of (Tb_(0.3)Dy_(0.7))Fe_(1.95) alloys was investigated using a new "one-step" process. The functional relation between the crystal growth rate and the traction velocity was determined by the analysis of heat transfer. Results demonstrate that the crystal grows synchronously with the traction velocity as the traction velocity U ≤ 360mm/h. When the thermal gradient G_L ≈ 100℃/cm and the solidification rate V = 70mm/h, samples with a <110> preferred orientation can be obtained. Samples with the <110> preferred orientation show a large low-field magnetostriction and an apparent compressive stress effect. With an increase in solidification rate, the crystal growth mode will transform gradually from the cellular and primary dendrite morphology into the developed dendrite morphology. Crystals growing in the cellular morphology have a <110> preferred orientation. In the primary dendrite, the preferred orientation is <113>. However, a poor magnetostrictive performance and failed preferred orientation are observed in the developed dendrite.