Пути повышения свойств заготовок деталей ГТД из жаропрочных титановых сплавов, полученных методом прямого лазерного выращивания

Today, additive technologies for the production of billets from heat-resistant titanium alloys are used in aircraft engine building and the aerospace industry. However, the mechanisms of structure formation and the level of mechanical properties in such blanks are poorly understood and are of interest. Currently, available data are not sufficient for the confident application of additive technologies in the production of aircraft engines. This paper evaluates the microstructure and substantiates the possibility of improving the mechanical properties of workpieces of GTE parts made of VT20 titanium alloy, obtained by laser-powder additive surfacing. For research, workpieces with a size of 215x120x4 mm 120x85x14 mm were grown. As a "building" material, a powder of spherical shape of particles was used, the chemical composition of which corresponds to the alloy VT20. The research results showed that during laser-powder growth in the VT20 alloy, the formation of "hardening" structures is observed, due to the accelerated heat removal into the previously formed layer of cast metal. In this regard, the strength of the alloy sharply increases, and its impact toughness and relative narrowing decrease. Note that stress relief annealing after growing (T = 750 ± 10 ° C, holding time - 1.5 ... 2.0 h.) does not significantly affect the level of mechanical properties. When the annealing temperatures rise to critical levels, significant structural changes are observed in the VT20 alloy, which in turn affects its mechanical properties. Based on the analysis of microstructures and the results of mechanical tests after distinct types of heat treatment (800 ° C, 850 ° C, 920 ° C, holding time - 60...75 min.), it was found that an increase in the plastic properties of the VT20 alloy is observed when the samples are heated to temperatures close to the temperature of the polymorphic transformation (960...1000 ° C). Annealing of workpieces after surfacing according to mode T = 920 ± 10 ° C, holding time - 60...75 min. allows to somewhat reduce the strength characteristics of the VT20 alloy, while increasing its impact strength and relative narrowing.

NON-DESTRUCTIVE CONTROL METHOD OF RELATIVE NARROWING AFTER RUPTURE

The paper presents the method of non-destructive determination of relative narrowing after rupture, based on the laws of elastoplastic indentation of a spherical indenter proposed by the authors. An acceptable accuracy of the method for engineering assessment of the plastic properties of carbon and alloyed structural steels is shown.

Donage and in Situ Annealing During Ion Implantation

ABSTRACTFormation of amorphous (α) layers in Si during ion implantation in the energy range 100 KeV–11MeV and temperature range liquid nitrogen (LN)-100°C has been investigated.Cross-sectional transmission electron microscopy (XTEM) shows that buried amorphous layers can be created for both room temperature (RT) and LN temperature implants, with a wider 100 percent amorphous region for the LN cooled case. The relative narrowing of the α layer during RT implantation is attributed to in situ annealing. Implantation to the same fluence at temperatures above 100°C does not produce αlayers. To further investigate in situ annealing effects, specimens already containing buried α layers were further irradiated with ion beams in the temperature range RT-400°C. It was found that isolated small α zones (< 50 Å diameter)embedded in the crystalline matrix near the two α/c interfaces dissolved into the crystal but the thickness of the 100 percent α layer was not appreciably affected by further implantation at 200°C. A model for in situ annealing during implantation is presented.