Hot Forming Limit Diagram For Titanium Alloy And Ti₂AlNb Intermetallics Sheets

Titanium alloy is wildly used in the aerospace, biotechnology, chemical and otherfields for its excellent oxidation resistance and specific strength under hightemperature conditions. But these materials also exist poor plastic and sprinkbacksignificantly at room temperature, it is necessary to research forming characteristics ofthe Titanium alloy and Ti2AlNb at high temperature.Researchers and engineers get theultimate strain at the different stress state from forming Limit Diagram, it is importantfor hot working technology and die design at high temperature。In this paper high temperature mechanical properties, the forming limit diagram atdifferent temperatures and Microstructure change of Ti2AlNb are mainly studied withthe background of research on hot forming limit diagram for titanium alloy andTi2AlNb.Obtaining the the true stress-strain curves and high temperature mechanicalproperties from the high temperature tensile test of the titanium alloy and Ti2AlNbintermetallic compound at designated temperature,analysis the effect of thetemperature for the high temperature mechanical properties and calculating theultimate strain of the left part of the hot forming limit diagram.Conducting sheets bulge forming experiments with totally enclosed heating by thesheets bulge formingdie and hot working technology. Cutting a reasonable sampleplate and depicting a2.5mm square mesh on it.Calculating the ultimate strainaccording to the formula and drawing forming limit curve for three materials atdifferent temperatures.Coming to the conclusion that forming limit curve of differentmaterials is higher with the temperature raising and TC4titanium alloy has the best hotformability.Measuring and calculating the thickness and thinning of Ti2AlNb bulging parts atdifferent temperatures,respectively the thinnest sheet thickness reach to0.76,0.78and0.72mm and the thinning is increasing with the temperature raising.The maximumthinning volume reached32%at temperature of900℃.Finally, researching the microstructure of Ti2AlNb under different stressconditions and temperature,original organizations of Ti2AlNb is a large number ofsmall chunks of O phase and α2phase distribution on the matrix of B2phase, the O phase is heterogeneous distribution and the α2phase distributing along the rollingdirecting on the matrix. With the temperature rising，the small chunks of O phaseturn to massive and α2phase turn to long strip.Different stress conditions mainlyeffect the O phase then the α2phase is almost invariant until the temperature reaching900℃.