Hardening by ion implantation of VT1-0 alloy having different grain size

The paper presents a transmission electron microscopy (TEM) study of the structural and phase state of commercially pure titanium implanted by aluminum ions. TEM study has been carried out for two types of grains, namely coarse (0.4 µm) and small (0.5 µm). This paper presents details of the yield stress calculations and the analysis of strength components for the both grain types in two areas of the modified layer: at a distance of 0-150 nm (surface area I) and ∼300 nm (central area II) from the irradiated surface. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a different effect on the yield stress in areas I and II. Thus, near the ion-alloyed layer, the yield stress decreases with the increase of the grain size, whilst area II demonstrates its increase. Moreover, the contribution to the general hardening of the alloy made by certain hardening mechanisms differs from contributions made by each of these mechanisms in each certain case

The effect of aluminum ion implantation on the grain size and structure of UFG titanium

Using the transmission electron microscopy technique, we have studied the structural-phase state of UFG titanium with an average grain size ~0.2 μm implanted with aluminum ions. An MEVVA-V.RU source has been used to implant the specimen at room temperature, implantation time 5.25 hours, and irradiation dose 1⋅1018 ion/cm2. To produce the UFG titanium samples, we have employed the combined multiple uniaxial pressing technique (abc-pressing) followed by grooved rolling and subsequent annealing at 573 K for one hour. The samples have been studied in two states: 1) before implantation (initial state) and 2) after implantation at a distance 70-100 nm from the sample surface. We have obtained the aluminum concentration profile of implanted α-Ti. It has been established that the maximum concentration of aluminum is 70 at.% and the thickness of the implanted layer is 200 nm. We have determined the grain distribution functions over the grain size, calculated the grain anisotropy coefficient before and after implantation. It has been established that implantation decreases the average longitudinal and transversal sizes of α-Ti grains, and reduces the anisotropy coefficient by three times. It has been established that aluminum implantation into titanium brings about formation of a whole set of phases with different crystal lattices, namely, β-Ti, TiAl3, Ti3Al, TiC, and TiO2

Modification of structural phase state and mechanical properties of poly-grained titanium alloy implanted by aluminum ions

The paper presents TEM analysis of microstructure, phase composition, and mechanical properties of commercially pure titanium. These properties of two types of grains are compared before and after modification of titanium by aluminum ions, namely: large grains (1.4 μm) and small (0.5μm) grains. The analysis shows that ion implantation results in a considerable improvement of mechanical properties of both large and small grains throughout their implantation depth. However, with increase of the grain size, the stress in the ion-modified surface layer decreases while in the subsurface layer it increases

Influence of the grain size on the dispersion strengthening of VT1-0 alloy implanted with aluminum ions

The method of translucent diffraction electronic microscopy conducted researches of a microstructure and phase structure of a titanic alloy of VT1-0 implanted by ions of aluminum. There are two types of grains; 1) large grains (LG) with an average size of 1.4 microns and 2) the small grains (FG) with an average size of 0.5 μm. It is established that as a result of radiation the ion-alloyed layer, on the basis of α-Ti grains is formed. The sizes, form and places of localization of secondary phases (Ti3Al, Al3Ti and TiO2) depend on the size of grain of a titanic matrix. The size of dispersive hardening of σor for different type of grains on depth of the ion-alloyed layer is calculated. It is shown that in MZ the size σor is provided only with TiO2 particles, in LG – generally TiO2 particles.</jats:p

Grain size effect on yield strength of titanium alloy implanted with aluminum ions

The paper presents a transmission electron microscopy (TEM) study of the microstructure and phase state of commercially pure titanium VT1-0 implanted by aluminum ions. This study has been carried out before and after the ion implantation for different grain size, i.e. 0.3 µm (ultra-fine grain condition), 1.5 µm (fine grain condition), and 17 µm (polycrystalline condition). This paper presents details of calculations and analysis of strength components of the yield stress. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a different effect on the yield stress. So, both before and after the ion implantation, the increase of the grain size leads to the decrease of the alloy hardening. Thus, hardening in ultra-fine and fine grain alloys increased by four times, while in polycrystalline alloy it increased by over six times

Peculiarities of structure and phase composition of V-Ti-Cr alloy obtained by sintering technique

Abstract Alloy of the V-Ti-Cr system is a promising material exploited under high radiation and in corrosion environment. We sintered V-4.9Ti-4.8Cr alloy from particles with original average size of 30, 280 and 200 μm, respectively for vanadium, titanium and chromium powders, by pressing of the powder mixture and its further sintering. The studies were undertaken using the methods of X-ray structural analysis, scanning electron microscopy with an energy dispersive analyzer and transmission electron microscopy. It was established that the structure of the alloy represented matrix grains (BCC solid solution), along the boundaries and at junctions of which the groups of oxycarbonitride particles of V, Ti, Cr (C,N,O) type of the variable elemental composition were arranged. The particles possessed a plate-like (0.4 x 2.0 μm) and rounded (0.5 μm) shape. The solid solution of the alloy was heterogeneous by concentration. This was evidenced by the complications of the diffraction patterns obtained from the corresponding sections of the structure. These were cords of main reflexes, satellites and emergence of a moire banded contrast in separate sections of the sample. Inside the matrix grains, there were nanoparticles (15 μm) of carbide V55Cr25C20, being a source of elastic internal local stresses

Structural-phase state of UFG-titanium implanted with aluminum ions

Transmission electron microscopy investigations were carried out to study the structuralphase state of ultra-fine grain (UFG) titanium with the average grain size of ~0.2 µm, implanted with aluminum ions. Implantation was carried out on MEVVA-V.RU ion source at room temperature, exposure time of 5.25 h and ion implantation dosage of 1⋅1018 ion/cm2. UFG-titanium was obtained by a combined multiple uniaxial compaction with rolling in grooved rolls and further annealing at 573 К for 1h. The specimens were investigated before and after implantation at a distance of 70-100 nm from the specimen surface. Concentration profile of aluminum implanted with α-Ti was obtained. It was revealed that the thickness of implanted layer was 200 nm, while maximum aluminum concentration was 70 at.%. Implantation of aluminum into titanium has resulted in formation of the whole number of phases having various crystal lattices, like β-Ti, TiAl3, Ti3Al, TiC and TiO2. The areas of their localization, the sizes, distribution density and volume fractions were determined. Grain distribution functions by their sizes were built, and the average grain size was defined. The paper investigates the influence of implantation on the grain anisotropy factor. It was revealed that implantation leads to the decrease in the average transverse and longitudinal grain size of α-Ti and decrease in the anisotropy factor by three times. The yield stress and contributions of separate strengthening mechanisms before and after implantation were calculated. The implantation has resulted in increase in the yield stress by two times

Microstructural Changes in Ni-Al-Cr-Based Heat-Resistant Alloy with Re Addition

This paper presents scanning and transmission electron microscope investigations of the structure, phase composition, and morphology of a heat-resistant alloy modified by thermal treatment and additionally alloyed by rhenium. The rhenium alloy was obtained by using the directional crystallization technique. The structural investigations were carried out for two states of the alloy, i.e., (1) original (after the directional crystallization); (2) after the directional crystallization with 1150 &deg;C annealing for 1 h and 1100 &deg;C annealing for 480 h. It is shown that fcc-based &gamma;- and &gamma;&prime;-phases are primary in all states of the alloy. The &gamma;&prime;-phase has an L12 structure, while &gamma;-phase is a disordered phase. It was found that after directed crystallization, the volume fraction of the &gamma;&prime; phase is ~85%, the fraction of the &gamma;-phase is less than 10%. Annealing leads to an increase in the &gamma;&prime;- phase up to 90%, the proportion of the &gamma;-phase practically does not change. Rhenium is a phase-formation element. The investigations show that high-temperature annealing modifies the structural and phase conditions of the heat-resistant alloy

Grain shape and size and structural and phase conditions modified by aluminum ion implantation in UFG titanium

The paper presents the transmission electron microscopy investigations of the granular state and the structural and phase conditions of commercially pure ultra-fine grain (UFG) titanium VT1-0 alloyed with aluminum ions. The UFG-titanium is obtained by the multiple uniaxial compaction with intermediate annealing. The ion implantation is carried out on Mevva-V.Ru ion source at ion-implantation dosages of 1·1017, 5·1017 and 1·1018 ion/cm2. The functions are constructed for the grain size distribution in longitudinal and cross sections; the average grain size and the grain anisotropy factor are determined in this paper. It is shown that the grain shape and size of titanium specimens are modified due to the ion implantation. With the increase of the ion-implantation dosage the anisotropy factor decreases three times. At 1·1018 ion/cm2 ion-implantation dosage the longitudinal grain size comes to 0.7 μm. The phase composition of the alloy is detected after the ion implantation and its modification induced by the implantation dosage. The quantitative characteristics and locations of secondary β-Ti, TiAl3, Ti3Al, TiC and TiO2 phases are ascertained during the investigations. It is shown that TiAl3 and Ti3Al are ordered phases formed during the ion implantation on α-Ti grain boundaries. The volume ratios of these phases are detected and determined by the ion-implantation dosage. The volume ratios of α-Ti and secondary TiC and TiO2 phases do not depend on the implantation dosage and range between 0.3-0.9 vol.%