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Annealing temperature have influence on the properties and organization of tungsten alloy rolling state

High-density tungsten alloy with high density, good strength and toughness and become one of the important material of military industry and civilian industry, especially as kinetic energy penetrator, balance weight components, inertial components, radiation shielding material has been widely used. WNiFe alloy due to its good ray shielding effect, is widely applied in medical industry, but due to the current production methods using isostatic pressing and mold pressing, and then processed into thin wire cutting way, caused a lot of trouble for production and waste of raw materials. Tungsten alloy deformation research of tungsten alloy forging, hydrostatic extrusion and rolling, etc., but rolling change form of tungsten alloy high hardness, high brittleness, caused a lot of inconvenience for later processing. The author wnife rolling state of 95 alloy as the research object, analyzes the microscopic fabric of different annealing temperature on the alloy and the influence of mechanical properties.


The experiment of raw materials is the reduction of tungsten powder, nickel powder and carbonyl iron powder. Three kinds of powder in 95 w3. 5 ni1. 5 fe (mass fraction), the proportion of mixing in the three dimensional mixer. After mixing with adhesive, using the moulding press forming, compact after dewaxing using liquid phase sintering got burned billet size is 130 mm * 105 mm * 3.86 mm, material relative density of 99% or more, using JM250 one-way rolling was carried out on the sintering billet reversing cold rolling mill, through multi-channel time, eventually material deformation of 89.9%, observe state sintering and the microstructure of materials change form, to change form 95 wnife alloy with 800 ℃, 1000 ℃, 1000 ℃ and 1200 ℃ four different annealing temperature and annealing time for 1 h, and the different annealing temperature of the alloy samples was performance tests, and observed the microstructure morphology, and analyses the influence of annealing temperature change form the influence of mechanical properties and microstructure of the alloy.


Sintering state base high-density tungsten alloy is made by tungsten particles hard phase and Ni - Fe bonding phase composition, tungsten particles into the approximate spherical uniform distribution in the binder phase, such as the rolling deformation for 89.9% of the plate along the longitudinal rolling deformation of the main direction of sampling observation of microstructure morphology, as shown in figure 2. Change form compared with sintering condition, after deformation tungsten particles significantly elongated, and with the increase of the deformation tungsten particles than showed a trend of gradual increase in the length of axis, and binding phase elongated gradually with the increase of the deformation.


Tungsten alloy after deformation reinforcement, in order to obtain more excellent comprehensive performance and improve the machining performance, usually to vacuum annealing treatment of alloy, in order to find the most appropriate annealing temperature, respectively, in 800 ℃, 1000 ℃, 1200 ℃ and 1450 ℃, holding time of 1 h, annealing on rolling state wnife 95 tungsten alloy is different annealing temperature of alloy microstructure morphology, after 800 ℃ and 1000 ℃ annealing treatment, the microstructure of alloy did not change, still keep rolling the microstructure morphology, tungsten particles and binding phase still for long strips of organization; When the 1200 ℃ after annealing treatment, tungsten particles appear a small amount of aggregation phenomenon, also as the change of tungsten particles aggregation is binding phase, 1200 ℃ annealing has a small effect on rolling state tungsten alloy microstructure, changed the rolling state structure of the alloy. When to raise the temperature to 1450 ℃, tungsten grain recrystallization occur, spherical, binding phase around the tungsten particles, and sintering of alloy microstructure morphology difference is not large, conventional tungsten alloy at 1430 ℃ in liquid phase, when the annealing temperature more than liquid temperature, alloy tungsten particles and the binding phase again to a state of sintering condition.


For sintering state, rolling state and different annealing temperature of rolling along the rolling direction respectively sampling testing tensile strength and elongation, table 1 shows that state sintered alloy, the tensile strength of the lowest of 850 mpa; Rolling state is the highest tensile strength, up to 1215 mpa, respectively after 800 ℃ and 1000 ℃ annealing, tensile strength and elongation of the alloy and the rolling state, tensile strength of 1215 mpa and 1210 mpa, respectively elongation is 3%, which is consistent with the microstructure morphology. When annealing temperature of 1200 ℃, the tensile strength of alloy began to reduce, up to 1050 mpa, and alloy elongation began to rise, to 8%, when the temperature continued to rise to 1450 ℃, the state has exceeded sintered alloy liquid point, tensile strength of alloy fell sharply, showing consistent with the basic sintering state levels, to 900 mpa, the elongation increased from 3% to 14%, from rolling state back to the sintering state level. Therefore, in order to get the best comprehensive properties of tungsten alloy, alloy for rolling condition can choose within the range of 800 ~ 1100 ℃ annealing temperature, but more than 1200 ℃ alloy rolling state will appear recrystallization phenomenon, to soften alloy, the intensity is reduced, but the increase of elongation.


Conclusion:


(1) the rolling deformation of 89.9% of the 95 wnife alloy after 800 ℃, 1000 ℃ annealing, the microstructure and properties of alloy and rolling state there is no difference, tungsten particles recrystallization phenomenon does not occur, the tensile strength of alloy remains at 1215 mpa, the elongation is 3%.


(2) when the annealing temperature is 1200 ℃, began rolling state alloy recrystallization phenomenon, the tensile strength of alloy decreased to 1050 mpa, the elongation increased to 8%.


(3) when the annealing temperature of 1450 ℃, the tungsten particle spherical, binding phase distribution around the tungsten particles, and sintering state organization, tensile strength and elongation of alloy sintered state level, 900 mpa and 14%, respectively.