Select titanium standard annealing process

In order to select a reasonable annealing process , we first observe the effect of heating temperature and cooling method on microstructure and mechanical properties of TC4 Titanium Alloy .

Test material 920 ℃ TC4 titanium alloy hot rolled bar , hot-rolled total deformation rate of about 80%, a + β / β phase transition point of 980 ~ 990 ℃. The sample at 1000 ℃, 950 ℃, 930 ℃, 830 ℃ , respectively, air cooled heat insulation , water and furnace cooling after 1 hour . Different ways of annealing on microstructure and mechanical properties are affected .

Which greatly affect the cooling rate on microstructure and mechanical properties of the four temperature microscopy . When water-cooled , 1000 ℃, 950 ℃ and 930 ℃ in equilibrium β -phase component were to happen martensitic transformation , β phase transformation to martensite a ` needle. At 1000 ℃ showed significant Wilcoxon organization whose mechanical properties of air-cooled 1000 ℃ data fairly . And water-cooled sample at 950 ℃ and 930 ℃, when the microstructure and characteristics are similar to air-cooled , but isometric is a ` needle β + martensite phase between a newborn titanium standard parts. At this point corresponds to the highest overall performance , and better creep resistance than air cooling organization . 830 ℃ thermal equilibrium β phase when the ingredients have not touch the M line , but the water-cooled intergranular β phase also found a very small needle transformation products , can only be distinguished by electron microscopy . But the structure of the product has not yet been measured needle . At this point the tensile strength and reduction rates are low. As furnace cooling , the sample was cooled slowly , long residence time at high temperature , sufficient for the polymorphic transformation , are all a phase become coarse . After cooling the furnace 1000 ℃ , a bulky sheet and a photo β phase grain boundaries in the original β -phase formed in a well strip thickness β grains within the original network , commonly known basket -like tissue . 950 ℃, 930 ℃ and 830 ℃ after furnace cooling , as a phase tends to a phase boundary in the original raw nucleation, growth , a microstructure are isometric and intergranular β phase . Tensile strength after 1000 ℃ lower than the furnace cooling air-cooled and water-cooled , higher tensile ductility . Overall performance in the other temperature furnace cooling are also lower than those in water and air .

In summary , in order to get the best TC4 titanium alloy strength and ductility performance, while there are good creep resistance and fracture toughness , can be incubated for 1 hour at 950 ℃ after air-cooled ( or water ) in the annealing process. In order to facilitate subsequent processing, metallurgical factory when the factory , TC4 titanium alloys are used in the 700 ~ 800 ℃ for 1 hour and air cooling technology medical titanium plate. For some large forgings , to ensure uniformity of performance , sometimes used by furnace cooling process .