ON THE PROBLEM OF GROWING TUNGSTEN SINGLE-CRYSTAL TUBES FROM THE MELT

The electron beam zone melting (EBZM) technique has been used to grow tungsten poly and single-crystal tubes in a specially designed unit. Single-crystal tubes has been grown on seed crystals with the <111> growth axis. Metallografic and X-ray structure analyses showed that the transverse cross-section of tubes displays several large subgrains separated by small-angle boundaries with misorientation not exceeding 1-2-degrees. The EBZM single-crystal tube growth process seems to be stable under capillary shaping conditions. Weak perturbation of the electron beam power causes new stationary values of the inner and outer diameter of the tubes. In a thin film approximation from the solution of the Laplace equation we have obtained the dependences relating the dimensions of growing tube with the seed crystal diameter and with the meniscus height of the melt. The growth angle was estimated.