The methods to optimize the grain size and uniformity of tantalum sheet include: Step 1. The tantalum ingots with a circular section are flattened by a fast forging machine at room temperature to obtain tantalum billets with a rectangular section; Step 2. Sawing to obtain tantalum blank with square cross-section shape; Step 3. After heat preservation, forge the gauge circle to obtain the bar blank with a circular cross-section shape; Step 4, the first annealing treatment, get the bar after annealing; Step 5, after heat preservation and extrusion, the slab with a rectangular cross-section shape is obtained; Step 6, the second annealing treatment, to obtain the annealed slab; Step 7, rolling, get the plate; Step 8, the third annealing treatment, to obtain the finished tantalum sheet. The method of the invention can realize the preparation of 5mm ~ 20mm medium-thick tantalum plate, the grain size is better than 6.5, the maximum grain size is less than 38μm, the grain size is uniform in the thickness direction of the plate, and the grain size difference between the surface and the core is less than 0.5.
Tantalum metal has high melting point, low vapor pressure, low evaporation rate at high temperature, low tough-brittle transition temperature (DBTT) and special dielectric properties, and can be widely used in the preparation of sputtering targets for integrated circuits. In addition, tantalum also has the characteristics of high density, certain tensile strength and good ductility, and has higher penetration compared with copper, and is also one of the ideal materials for drug type covers. Because the size and uniformity of the grain directly affect the performance of the sputtered film and the performance of the coating, as the grain size is smaller, the deposition rate of the sputtered film is higher and the uniformity is better, and the armor piercing power of the coating is also higher. The sputtered target and tantalum plate used for the coating put forward high requirements on the internal microstructure of the plate.
At present, the use of multiple forging combined with rolling process to prepare the finished sheet with a thickness of less than 5mm has the characteristics of basically uniform microstructure and grains, and the smaller the thickness of the sheet, the finer the grains. However, the existing technology can not ensure the fineness and uniformity of grain size in the thickness direction when preparing a plate with a thickness greater than 5mm, so that the finished plate not only has a grain size of more than 50μm, but also has a grain size difference greater than 2 levels in the thickness direction, which can not meet the rapid development of integrated circuits and the needs of the heavy blow of the drug shield.
