The particle shape of titanium powder is spherical, polygonal, sponge-like and flake-like, etc. The particle shape is related to the method of preparing the titanium powder. The requirements for titanium powder generally include three aspects, namely purity, particle size and particle shape.
There are several ways to add titanium to aluminum alloys. One is to add intermediate titanium alloys in block or wire form; the second is to add titanium additives, which is to add titanium; the third is to add refiners, which are specially refined. The casting structure is not an alloying element, and no composition analysis is performed.
(1) Titanium additives. The titanium additive is to adjust the titanium content in the aluminum alloy. It is pressed into block or cake with titanium plus aluminum powder or flux salt. Among them, the titanium powder content is 55%-75%, and the aluminum powder or flux salt is 45%-25%, which is put into the molten aluminum alloy according to the demand. If such additives use flux salts as ingredients, they should be careful not to absorb moisture or moisture. In fact, the flux salts in the product are useless. It is most suitable to add packaged pure metal powder.
(2) Titanium refiner. The element of the titanium refiner in the alloy is not a component of the alloy, but an element that refines the structure during the smelting and casting process. It is mixed with titanium powder and salt chemicals and pressed into a block or cake for supply. There are generally three kinds of titanium content. 30%, 40% and 60%, while adding boron-containing salt (boron content is 1%, 2%, 3% or 4%), and the rest is prepared with NaCl and KC1. The market supplies Ti40B4, Ti30B4, Ti30B3 and Ti60Bl products.
Among more than 150 types of deformed aluminum alloys, about 120 grades are added with titanium, but the number of people added is not much, between 0.02% and 0.4%. Among about 40 kinds of cast aluminum alloys, there are 13 grades with titanium added, generally 0.08%-0.35%. The main purpose of adding titanium is to refine the casting structure and weld structure, reduce the tendency of casting cracks and improve the mechanical properties. The role of titanium addition is to form a compound TiAl with aluminum, which acts as a non-spontaneous core to refine the casting structure when the aluminum alloy is solidified. Sometimes a small amount of B is added with Ti to form a TiB2 compound to promote the refinement of Ti.