Titanium Phase transition temperature of testing

GR2 industrial pure titanium with good corrosion resistance, mechanical property and welding performance, in ship, chemical industry, and many other fields have important applications.Because the metal under the condition of the machining process must be, its organization status mainly depends on the organization in the process of evolution, heat treatment and strongly influence its performance.High temperature, therefore, the research of industrial pure titanium GR2 organization evolution behavior has important significance.In this paper, using the confocal laser scanning microscope (CLSM), optical microscope (OM), differential scanning calorimetry (DSC) method to study the isometric state of industrial pure titanium GR2 in organization evolution behavior in the process of heating, heat preservation and cooling, analyses and summarizes its organizational evolution law.In heating and heat preservation phase, bending part of alpha grain boundary migration and tend to be straight, short heating effect on alpha grain size is very Titaniumcn small.Temperature at the initial phase transition point T alpha/alpha + beta above multiple parallel "lenticular" in the same alpha beta strip around the intracrystalline nucleation and diffusion mechanism to gobble up alpha growing, with "tent" embossed on the surface of the form.Temperature more than completely alpha + beta phase transition point T/beta, alpha and beta phase change over, initial alpha beta article slices with crystal and to form a "group", continue to heat, the "group" "eat" to each other, eventually become the bulky shaft such as beta.The dynamics of beta grain grew up statistics and fitting calculation.From the state of the different cooling, different organization at room temperature.From the alpha + beta two-phase district cooling, such as organization revert to the original state axis, floating on the surface of convex disappear;From cooling, just completely into beta phase formation interface irregular alpha organizations;From cooling, axis beta groups such as alpha and beta and alpha phase change can be divided into grain boundary westergren alpha two phase nucleation and grain boundary first alpha in beta at grain boundary nucleation and growth to connect into a thin film of grain boundary alpha, then westergren alpha on the grain boundary alpha nucleation, and in the form of a layer of flake cluster to grew up in the beta phase, until full of beta grain, beta and alpha end of shift, forming a typical widmanstatten structure.Cooling rate equivalent shaft beta beta and alpha phase transition in the process of cooling effect is very big, the faster the cooling rate, grain boundary alpha and westergren alpha thickness is smaller, westergren alpha elongation the faster, the faster the phase transition.Under different cooling rate on the grain boundary of alpha broadening, the elongation and the thickness of the westergren alpha, and beta and alpha phase transformation kinetics of quantitative statistics, beta and alpha phase transformation kinetics of empirical formula is given.

Using the calculation method and differential scanning calorimetry and continuous heating metallographic method
Three kinds of method to calculate and determine the two-phase titanium alloy TC11 (alpha + beta)/beta phase transition point.Calculation method for each element and the influence of impurity element content on the phase transformation point value is within the scope of a content calculated value, thus calculated is close to the phase transition point and the measured values;Differential scanning calorimetry because of titanium alloy and chemical reaction of the crucible, produce transformation hysteresis phenomenon, cause the measured phase change temperature is too high;Metallographic method and continuous warming choose smaller due to the quenching temperature interval, measuring accuracy is higher, therefore more accurate measurement of TC11 titanium alloy phase transition temperature.Use the synchronous sTA449c thermal analyzer measurement titanium and titanium alloy phase transition temperature, the reference sample for 23 alo powder, 1 min to 10 ℃ temperature;The protection of argon flow for 45 m11min.Before test, should be first in the two samples in the crucible of 23 alo powder amount, measuring instrument baseline within the rules, can begin formal sample DSC curve.The phase transition temperature was evaluated by continuous heating metallographic method.The sample size to 10 mm x 10 mm x 10 mm;When heating sample to ensure heat through, time of heat preservation for 60 min.Quenching temperature range is 990 ~ 1040 ℃, quenching temperature interval of 10 ℃, and then water quenched sample.Of which the transfer speed of no more than 2 s.After quenching specimen made of metallographic observation, the optical microscope magnification of 500 times the sample organization change.2.1 calculation method according to the phase transition temperature of each element titanium phase transition point of the influence of the phase change temperature calculated formula is: / T + phase transformation point = 885 ℃ + Σ content of each element x (1) the effect of the elements of phase transformation point of the type of 885 ℃ for calculating the phase transition point of pure titanium.