The work represents the results of mechanical tests and structuralphase analysis of the 1441 (AlCuMgLi) alloy laser weld joints. Synchrotron X-ray diffraction showed that laser welding causes the formation of T3 and T2 phases instead of strengthening δ' phase in weld material. Applied post-weld heat treatment (PWHT) restored the original phase composition but led to ~5 times growth of the δ' phase precipitates. As a result, weld joints returned and even exceeded the ultimate yield tensile strength of the base alloy but their tensile strain was notably lower. Fatigue tests demonstrated that the obtained weld joints had high fatigue resistance significantly exceeding riveted joints even before PWHT. Heat treatment increased fatigue resistance at high loads but reduced this property at low load.

This paper presents the results of in situ investigation of Al-Cu-Li-Ag alloy (V-1469) in initial state and after laser welding. The study was performed via synchrotron X-ray diffraction accompanied by transmission electron microscopy and differential scanning calorimetry. The behavior of main strengthening phases T-1 (Al2CuLi) and Omega (Al2Cu) were in focus. It was found that they act differently in the initial alloy and in the weld material. The T-1 phase was more thermally stable in the initial alloy and decomposed at much higher temperature than in the weld material. The Omega phase doesn't decompose completely in the initial alloy up to similar to 600 degrees C due to, presumably, its stabilization after the T-1 decomposition. In case of the weld material this phase isn't present initially but forms after heating and consequent cooling.

To this day, the structural strength of laser-welded joints of Al-Li alloys made with a fiber laser has not been thoroughly studied. In this research, high-strength laser-welded joints of Al-2.7Cu-1.8 alloy were obtained using a fiber laser followed by post-weld heat treatment. The laser-welding process parameters were optimized, including welding speed, radiation power, and location of the focal spot. In addition, the influence of these parameters on the microstructure of the welded joints has been studied. After welding, the welded joints were heat treated (PWHT) in two modes to achieve optimal mechanical properties. Changes in the structural and phase composition of the weld material before and after PWHT were examined using synchrotron diffraction and transmission electron microscopy. The obtained research results have shown that during laser welding, copper-containing phases formed at the boundary of dendrites in the weld material, which leads to a reduction in strength. The process of post-weld heat treatment (PWHT) has led to the restoration of the phase composition in the material of the weld. The cyclic (fatigue strength), dynamic (crack strength), and static (yield strength and ultimate tensile strength) properties of laser-welded joints after PWHT have been studied. It has been observed that PWHT using mode 1 allows to achieve maximum fatigue and dynamic properties, while PWHT using mode 2 results in achieving maximum static properties at various temperatures.

We studied the evolution of the phase composition of laser welded joints before and after heat treatment of 3rd generation Al–Li alloys using synchrotron radiation. The article demonstrates the fundamental role of the alloying elements of copper and lithium in formation of the phase composition of the fusion zone of the weld. It has been established that laser exposure changes the phase composition of the alloy. Namely, low copper contents mainly lead to formation of T2(Al6CuLi3) and T3(Al5CuLi3) phases, the average copper contents form T1(Al2CuLi), T2(Al6CuLi3), T3(Al5CuLi3) phases and the presence of high copper contents results in formation of T1(Al2CuLi) phase at the boundaries of dendrite. Post-heat treatment restores the initial phase composition in the fusion zone. As for the solid solution, the δ'(Al3Li) phase is formed at low copper contents, the δ'(Al3Li) and T1(Al2CuLi) phases are formed at average copper contents, and T1(Al2CuLi) phase is observed at high copper contents. Consequently, this makes it possible to improve the mechanical properties of weld joint specimens to match the numbers of the initial alloy.

Butt joints of the V-1461 and 1424 heat treated aluminum-lithium alloys of the third generation were welded with a CO2 laser and studied in detail for the first time. In particular, spatial distributions of the formed phases and their evolution upon post-weld heat treatment (PWHT), determining the mechanical properties of the joints, were investigated. The PWHT included quenching and subsequent artificial aging. The key factors, affecting the metallurgical processes in a weld pool, were the following: 1) the alloying elements and the thermal properties of the alloys, 2) the dynamics of the local non-equilibrium melting, the convective transfer of the molten metal in the weld pool and its subsequent solidification, 3) the cooling rate, and 4) the PWHT procedure. By using synchrotron radiation and scanning electron microscopy, new theta(Al2Cu), T1(Al2CuLi) and S1(Al2MgLi) phases were found in the weld metal that were absent in both base metals. This phenomenon reduced the mechanical properties of the joints to the levels, corresponding to about 50 % of the 1424 alloy as the weakest one. Quenching contributed to the formation of the delta '(Al3Li) strengthening phase in the weld metal. As a result, the ultimate tensile strength increased up to 70 % and elongation up to 95 % of the corresponding levels of the 1424 alloy. Artificial aging made it possible to form the T1(Al2CuLi) strengthening phase, to increase the content of the delta '(Al3Li) one, as well as to improve the mechanical properties of the joint. In this case, the ultimate tensile strength was 411 MPa, the yield point was 327 MPa and elongation was 1.7 %. These values were close to those for the 1424 alloy (about 80 %, 89 % and 23 %, respectively).

The paper presents experimental studies on laser cladding synthesis of a titanium matrix composite based on Ti64 titanium alloy and TiB 2 ceramic reinforcement. The weight percentage of TiB 2 ceramics in the composite was 5, 10 and 15%. The phase composition of the resulting materials was analyzed by standard X-ray diffraction and synchrotron X-ray diffraction. It was found that the structure of the titanium matrix composite with 5 wt % ceramics consists of TiB nanowhiskers, and that of samples with higher ceramic content exhibits TiB whiskers with a width of several micrometers. The addition of TiB 2 ceramics increases Young’s modulus, nano- and microhardness of composite samples compared to Ti64 alloy. The indentation method was used to study the formation of a phase that is different from TiB 2 ceramics and TiB microwhiskers and has elastic properties exceeding the elastic properties of the original Ti64 matrix phase. Analytical predictions showed an increase in the effective elastic properties of the formed heterogeneous material with the predicted new phase. It was also found that a lower friction coefficient can be achieved by forming a structure with nanowhiskers, while higher Young’s modulus and microhardness can be obtained by forming a structure with microwhiskers.

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This work presents a study on the additive manufacturing of functionally graded metal-ceramic materials based on Ti64 with boron fibers and particles. For the first time, the phase composition of the obtained composite was investigated using synchrotron radiation. It was shown that during laser exposure and in situ synthesis, boron dissolves in the titanium matrix, forming secondary compounds such as TiB and TiB2. An increase in the microhardness of the formed material compared to the titanium alloy was established. High-speed impact tests on the Ti64-B samples were conducted using an electrodynamic mass accelerator. It was shown that the use of boron fibers in the metallic matrix reduces the depth of the crater created during impact testing by 40% compared to the Ti64 reinforcement-free coating.

The paper presents the results of both microscopic and synchrotron X-ray diffraction analysis of the microstructure of the dissimilar Ti-6Al-V-Mo-Zr/Al-Cu-Li butt laser welds, as well as their mechanical properties. While the thickness of the welded plates (2 mm), the power (1.2 kW) and velocity (1 m/min) were constant, the variable parameter has been the laser beam offset towards the titanium alloy plate (from 0 to 1 mm). The offset has replaced a conventional joining process (via mixing both molten base metals) into a welding-brazing. The conventional joints have consisted of a separate aluminium melting zone (Al FZ) and a mixing zone (MZ). The Al FZ has contained typical secondary aluminium alloy phases and the TiAl3 intermetallic particles, while the alpha 2Ti3Al, beta 2-Ti and gamma TiAl compounds have been found in the MZs. With rising the beam offset value, mechanical tests have shown an increase in the ultimate tensile strength of the welded joints from 74 up to 168 MPa.

The deposition process of a nickel-based cermet coating with a high (60 wt.

An overview of laser welding methods and additive manufacturing technologies used in modern mechanical engineering is given, and the main trends and aspects of these technologies are discussed. Laser welding processes of thermally hardened aluminum alloys and problems of obtaining high-strength welded joints are considered. The additive growth of heterogeneous materials is analyzed taking into account the dimensionless parameters determining the structure of materials fabricated by additive manufacturing.

The paper presents the results of experimental studies on the synthesis of a metal-matrix composite by direct laser deposition, including the assessment of optimum irradiation modes to make such a material free of defects (pores, cracks, etc.). It is shown that in-situ synthesis is provided by laser irradiation of a powder mixture composed of polycrystalline boron and titanium alloy Ti64 in a ratio of 1 : 9 wt %. According to X-ray diffraction analysis with synchrotron radiation, scanning electron microscopy, and nanoindentation, the deposited material contains second phases in the form of TiB and TiB2 ceramics. According to mechanical tests, the elastic modulus and the hardness of the Ti64 metal matrix are E-av = 159.7 GPa and H-av = 7 GPa, and those of synthesized particles (whiskers) are E-av = 321.6 GPa and H-av = 19.7 GPa, respectively.

The paper presents the results of both microscopic and synchrotron X-ray diffraction analysis of the microstructure of the dissimilar Ti-6Al-V-Mo-Zr/Al-Cu-Li butt laser welds, as well as their mechanical properties. The variable parameter has been the laser beam offset towards the titanium alloy plate, which has changed a conventional joining process (via mixing both molten base metals) into a welding-brazing. The conventional joints have consisted of a separate aluminium melting zone (Al FZ) and a mixing zone (MZ). The Al FZ has contained typical secondary aluminium alloy phases and the TiAl 3 intermetallic particles, while the α 2 Ti 3 Al, β 2 -Ti and γTiAl compounds have been found in the MZs. With rising the beam offset value, mechanical tests have shown an increase in the ultimate tensile strength of the welded joints from 74 up to 168 MPa.

Results of an experimental study of the strength characteristics and structural-phase composition of a nondetachable connection of dissimilar materials based on thermally hardened aluminum alloys D16T of the Al-4.4Cu-1.5Mg system and 1420 of the Al-5.2Mg-2.1Li system obtained by butt-end laser welding are reported. The phase composition of the welded joint is studied with the use of synchrotron radiation by the method of transmission diffraction. The welded joint microstructure is considered by optical microscopy. It is demonstrated that heat treatment (quenching and artificial aging) allows one to improve the chemical properties of the welded joint.

Diagnostics of the structure of materials is necessary for determining subsequent technological operations in the production of finished products. In the present paper, we propose to use synchrotron radiation for investigating the phase composition of metal-ceramic coatings with a titanium alloy as a matrix and powdered titanium boride as reinforcing elements. A comparison of the results obtained from the diffraction of x-ray tube radiation (Cu) and synchrotron radiation has shown that when it is necessary to determine the phases containing light elements (in the present case B), diffraction of synchrotron radiation makes it possible to unambiguously reveal TiB in the resulting coating, whereas diffraction of x-ray tube radiation could not allow unambiguous interpretation of results. Thus, the advantage of the synchrotron radiation in diffraction studies has been shown.

A technology has been developed for laser welding of dissimilar materials based on the Ni-Fe-Cr and Fe-C-Mn-Si systems, which can replace the technology of brazing joints between a diamond unit and a steel tube in crown drill bit manufacturing. The optimal parameters for obtaining welded seams without internal defects using laser radiation were determined. The amount of heat input as well as the energy per unit volume of the molten material were also calculated. It was found that the use of optimal energy modes of laser treatment made it possible to avoid the destruction of diamonds during the welding process. Welding led to the formation of martensitic structures in and around the weld. Despite this, preliminary tests of the crown drill bit showed the advantage of a laser-welded joint over a brazed one.

The purpose of these investigations was to study the effect of heat treatment on the structure and the phase composition of laser welded joints of the Al-2.8Cu-1.7Li alloy (V-1461 grade), providing the maximum tensile strength. To study the phase composition of the weld metal, synchrotron radiation was applied using a 'Mega Science' facility. This enabled to assess the phase distribution across the weld metal before and after heat treatment. It was found using high-resolution scanning and transmission electron microscopy, energy dispersive X-ray analysis, and synchrotron X-ray diffractometry that the T-1(Al2CuLi) and T-2(Al6CuLi3) main phases had been formed in the weld metal and at the interfaces with the matrix. Ultimate tensile strength of the welded joints was about 341 MPa, which was 62% of that of the base metal. Subsequent heat treatment of the welded samples, included hardening and artificial aging, caused the homogenization of the Al-Cu-Li alloy solid solution, as well as the formation of the delta' (Al3Li) hardening phase. Also, the T-1 and T-2 phases were formed partially. After quenching, tensile strength of the welded joints improved and was about 85% of that of the base metal. After artificial aging, it was about 510 MPa and approached tensile strength of the base metal (93%).