Preparation of Terfenol-D with precise 〈110〉 orientation and observation of the oriented growth crystal morphology

Abstract

In a super high temperature gradient directional solidification equipment developed by the authors, φ7 mm rare earth giant magnetostrictive rods with precise 〈110〉 orientations were manufactured successfully without any seed crystal. A dispersion of only 3° exists between the 〈110〉 oriented growth direction and the axis of the rod. During the directional solidification process, there exists a certain relationship between the crystal growth morphology and the crystalline orientation degree. The crystallites’ orientation degree can be determined conveniently through the observation of the crystal morphology. Under the condition of the temperature gradient of 800 K/cm and the withdrawal velocity of 6 μm/s∼10 μm/s, Tb 0.27Dy 0.73Fe 1.9 rod with 〈110〉 oriented crystals can be obtained when the solidified part of the rod reaches 20 mm. When the length of the solidified part is at least 30 mm, the 〈110〉 oriented crystallines can grow in a stable way.