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The energy balance of laser cutting of low-carbon and stainless steel sheets with the minimum roughness of the cut surface is experimentally studied. Experimental data obtained in wide ranges of cutting parameters are generalized with the use of dimensionless parameters (Peclet number and absorbed laser energy). It is discovered for the first time that the minimum roughness is ensured at a certain value of energy per unit volume of the melt (approximately 26 J/mm), regardless of the gas type (oxygen or nitrogen) and laser type (fiber laser with a wavelength of 1.07 μm or CO laser with a wavelength of 10.6 μm). [ABSTRACT FROM AUTHOR]

A study has been made of the physicomechanical properties of a heterogeneous material based on TiB, TiB2, TiC, and B4C ceramics and a Ti–6Al–4V metal alloy formed by the method of selective laser melting. Consideration has been given to the influence of TiB, TiB2, TiC, and B4C ceramic particles produced by in situ synthesis in the process of laser action on the microstructure and hardness of the formed metal-matrix composite. Basic mechanisms of variation in the microstructure to form secondary ceramic inclusions were discussed and microhardness measurements at a macro- and nanolevel were carried out. It has been established that ceramic particles formed as a result of the in-situ synthesis improve sharply the hardness of the metal-matrix composite depending on the composition of the ceramics. [ABSTRACT FROM AUTHOR]

For the first time, experimental investigations of the resistance of a cermet coating formed by a combined method (cold gas-dynamical spraying with subsequent laser treatment) to high-speed impact was carried out. It is shown that as a result of laser interaction of TiAl–B4C with cold gas-dynamically deposited coating, boron carbide particles dissolve in the metal matrix, and secondary phase compounds of TiC and TiB2 are formed. Measurement of microhardness showed that created cold gas-dynamically deposited coating, involving B4C, Ti, and Al, has a microhardness of 466.3 HV0.3, while the microhardness of a coating after laser treatment is equal to 1331.3 HV0.1. Investigation of highspeed impact has shown the influence of formed coatings on the size of the crater in the substrate. It is also shown that the created cermet coating (cold gas-dynamical deposition + laser radiation) decreases the crater depth in the substrate by more than twice, with the crater width decreasing by 1.4 times compared with a sample without coating. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the experiments with laser-produced plasma jets the main processes of their interaction with transverse magnetic field were studied to simulate various plasma injections in space and the effect of influence of dilute background plasma onto electric drift motion of jet was reproduced and investigated experimentally for the first time [Copyright &y& Elsevier]

Results of theoretical and experimental investigations of physical and mechanical properties of a heterogeneous material based on the TiB ceramics and Ti–6Al–4V metallic alloy obtained by means of selective laser melting are reported. Elastic properties of the heterogeneous structure under analysis are described by the method of conditional moments. Young's modulus of the created heterogeneous material based on the titanium alloy and titanium boride is measured. The experimental data are found to be in good agreement with the numerical predictions. [ABSTRACT FROM AUTHOR]

• When cutting with a high power pulsed laser using argon, an optical breakdown of the gas occurs. • Part of the laser power is put into the material through the plasma of an optical discharge in argon (laser-plasma cutting). • Laser-plasma cutting of aluminum-lithium alloys with a thickness of 1.5 and 2 mm provides a low roughness cut at an argon pressure of 0.5 bar. • The spatial structure of the cut surface is grooved when using argon and grainy when using air. • When cutting with air, the plasma torch is not observed, on the samples there is a dross. The effect of assist gases (argon or air) on the quality of edge surfaces of aluminum alloys cut with a pulsed Q-switched CO 2 laser was experimentally investigated. Sheets of both Al-Mg-Li and Al-Cu-Li alloys with thicknesses of 1.5 and 2.0 mm were cut. It was found that the morphologies of the cut-edge surfaces were significantly different after cutting with argon and air. For the first time, the cutting process was carried out using a laser-plasma mode, when an optical discharge was maintained in an argon flow. At an argon pressure of 0.5 bar, the cut-edge surfaces were without dross and their roughness were significantly lower than that after cutting with a continuous wave laser. Severance energy levels were similar for both laser-plasma and continuous wave cutting modes. [ABSTRACT FROM AUTHOR]

• Dissimilar Ti-Al-V/Al-Cu-Li and Ti-Al-V/Al-Mg-Li welds were obtained by a CO 2 laser. • The optimal laser beam offset was determined to weld the high-strength joints. • The chemical composition of the aluminum alloys affected the strength of the welds. • Copper significantly increased the strength of the welds in contrast to magnesium. This paper presents the results of the studies of dissimilar Ti-Al-V/Al-Cu-Li and Ti-Al-V/Al-Mg-Li laser welds. The main variable parameter was the laser offset towards the titanium alloy. It was found that strength properties of the welds were significantly affected by alloying elements (copper or magnesium) in the aluminum alloys. The presence of copper improved kinetics and thermodynamics of the welding process due to the formation of specific phases in the fusion zone. Also, it increased the strength of the dissimilar welds by 2.5 times compared with the Ti-Al-V/Al-Mg-Li joints. [ABSTRACT FROM AUTHOR]

Microstructure of laser welds of the X70 low-carbon pipe steel was studied. High cooling rates after laser welding and non-uniform distribution of carbon in the ferrite-pearlite base metal caused formation of regions with increased microhardness (up to 650 НV) in inter-critical heat affected zone (ICHAZ). These regions consisted of finely dispersed degenerate upper bainite and martensite-austenite constituents of a slender shape and small fraction of a massive shape along the boundaries of bainite laths, as well as twinned martensite. High concentration of martensite-austenite constituents (10–16%) and residual stresses in ICHAZ, as well as a dendritic martensitic structure with carbide interlayers along the boundaries of martensite laths in fusion zone were the main reasons of sharp decrease in charpy impact energy of the welded samples. High microhardness of the laser welds was decreased down to 320 HV and their brittleness was improved by annealing. Also, in ICHAZ, degenerate upper bainite and the regions of martensite-austenite constituents decayed forming tempered sorbite and Fe 2 C and Fe 3 C carbides, respectively. Charpy impact energy of the welds doubled after annealing compared to the welds without annealing, and ductile-brittle transition temperature decreased down to –60°С. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental study of the microstructure and microhardness of a functionally gradient material fabricated from 316L stainless steel and tungsten carbide (WC) ceramic particles by the selective laser melting method. High-quality defect-free cermet coatings with different ceramic contents were obtained. Optical and scanning electron microscopy and energy dispersive analysis show that laser processing leads to dissolution of WC ceramic particles. The produced coating has a dendritic structure and contains iron- and chromium-based carbides. The coating microhardness is in the range HV0.3 = 280 – 430. [ABSTRACT FROM AUTHOR]

This paper explores the structure and phase composition of laser welded joints of Al-Cu-Li alloy without and after post heat treatment (annealing, quenching, and artificial aging). Changes in the structure and phase composition of welds and the base alloy before and after heat treatment are studied using scanning electron microscopy, X-ray diffractometry, and synchrotron radiation diffraction. The investigation results have shown that the formed agglomerates of intermetallic particles are mainly represented by the Т1(Al2CuLi) phase. The change in the strength of the Al-Cu-Li alloy samples after laser welding and heat treatment is not due to the absence or presence of the strengthening Т1(Al2CuLi) intermetallic phase but rather due to the different localization of particles of this phase in the weld joint. The segregation of the phase at dendritic grain boundaries leads to a significant strength decrease, and, vice versa, its homogeneous distribution in the solid solution achieved by post heat treatment (annealing, quenching, and artificial aging) increases the strength of the laser welded samples. [ABSTRACT FROM AUTHOR]

Results of experimental investigations of welded joints of high-strength aluminum-lithium alloys of the Al-Cu-Li and Al-Mg-Li systems are reported. The welded joints are obtained by means of laser welding and are subjected to various types of processing for obtaining high-strength welded joints. A microstructural analysis is performed. The phase composition and mechanical properties of the welded joints before and after heat treatment are studied. It is found that combined heat treatment of the welded joint (annealing, quenching, and artificial ageing) increases the joint strength, but appreciably decreases the alloy strength outside the region thermally affected by the welding process. [ABSTRACT FROM AUTHOR]

A method is proposed for creating principally new functionally graded heterogeneous materials on the basis of BC ceramic powders with different mass fractions in the original mixture and plastic metallic additive of Ni by a combined method of cold spraying with subsequent layer-by-layer laser treatment. Mechanical properties of the resultant tracks are examined. It is shown that the track microhardness increases with increasing BC concentration in the original mixture. The track structure is found to depend on the size of ceramic particles in the interval from 3 to 75 μm. Reduction of the BC particle size (approximately by a factor of 2-3) inside the track owing to fragmentation under the action of the laser beam is observed for the first time. [ABSTRACT FROM AUTHOR]

The acoustic-emission method for inspecting flaws that form during laser bonding with the use of a CO continuous-wave laser with a power of up to 8 kW and characteristics that can be preadjusted prior to welding is considered. The structure of acoustic-emission signals registered in a specimen's flawed domain has been analyzed using the wavelet transform. It has been shown that the structural coefficients of the acoustic-emission signals localized in specimen's flawed sections become identical over time. [ABSTRACT FROM AUTHOR]

In this study, certain technological variants of the laser welding of alloy 1424 of the Al-Mg-Li-Zr system are considered with the purpose of obtaining the durability level of the welded joint, which is close to that of the basic metal. It is shown that, in the case of using various types of plastic deformation of the welded joint, its durability can be increased considerably to 0.85-0.95 from that of the basic metal. [ABSTRACT FROM AUTHOR]

Results of an experimental study of properties of joints obtained by using different regimes of laser welding of the 1424 alloy (Al-Mg-Li) are reported. The strength and structure of the welded joints are determined. The influence of various types of welded joint straining on its strength is studied. It is demonstrated that the joint strength increases in the case of plastic straining. [ABSTRACT FROM AUTHOR]

The quality of cutting of low-carbon and stainless steel by beams of fiber and CO lasers with oxygen or nitrogen being used as a process gas is compared. The cut surface roughness for sheets from 3 to 10 mm thick is determined. Domains of optimal (in terms of the minimum roughness criterion) application of lasers of various types in the space of dimensionless parameters (Peclet number and dimensionless power) are found. It is demonstrated that the CO laser is more effective for laser-oxygen cutting, while the fiber laser is more beneficial for cutting with the use of a neutral gas. [ABSTRACT FROM AUTHOR]

In this paper, the heat affected zone (HAZ) of laser welded joints of the X70 steel were studied by the transmission electron microscopy method. The effect of the initial microstructure (coarse-grained hot-rolled and fine-grained after cross-helical rolling) on the HAZ formation and the mechanical characteristics of the welded joints were shown. It was found that the microstructure in the inter-critical HAZ of the steel after cross-helical rolling was more dispersed, homogeneous, and uniform compared to that of the coarse-grained hot-rolled one due to the initial fine-grained ferrite-bainitic-pearlite microstructure and the absence of pronounced ferrite-pearlite banding in the base metal. The character of the microhardness value distribution in the HAZ of the steel after cross-helical rolling was smooth with the gradual decrease from 370 down to 185 HV as shifted towards the base metal. In the HAZ of the coarse-grained hot-rolled steel, the heterogeneous microhardness value (up to 640–670 НV) distribution was revealed. The reason was the upper degenerate bainite microstructure with high residual stresses, characterized by laths up to 2.0–2.5 μm long and a high martensitic-austenitic constituent fraction (10–16%) of a slender shape along the boundaries of bainite laths. The conclusion was drawn that one of the ways to reduce the brittleness of the laser welded joints could be using the initially fine-grained steels possessing the homogeneous (mainly bainitic) microstructure. [ABSTRACT FROM AUTHOR]