The effect of synthesis of the starting powders on the properties of Cu-Ti-TiB2 alloy obtained by laser melting

A comparison was made between layer-by-layer laser melting (LM) of two types of feedstock powders: (1) elemental powder blend and (2) mechanically alloyed powder. LM was done by Nd:YAG laser at 1064 nm (max. average power 100 W) in argon ambience. Samples synthesized were Cu-Ti-TiB2 rectangular tracks (20x6x1 mm), and input parameters of the process: powder layer thickness 100-250 µm, hatch spacing 1 mm, pulse length 4 ms, energy 4 J, pulse repetition rate 20 Hz. Part of the samples was heat-treated in argon at 900 °C, 10 h. Structural characterization of the samples was done using light microscope and scanning electron microscope (SEM). Chemical analysis of the as-obtained laser melted samples was done by inductively coupled plasma-atomic emission spectrometry (ICP-AES). It was established that the microstructure of LM samples was comprised of Cu-Ti and Cu-B solid regions, and in situ formed microparticles of primary TiB2. Only after high-temperature thermal treatment has the secondary TiB2 occurred. Tensile tests showed much higher strengthening in heat-treated samples with mechanically alloyed powder as starting material, where the formation of secondary TiB2 nanoparticles was considerable

Microstructures and Mechanical Properties of ZA27-Al2O3 Composites Obtained by Powder Metallurgy Process

This paper describes a study of the microstructures and mechanical properties of Zn-matrix composites reinforced by 10 wt.% Al2O3 particles of 0.7 mu m average size. Commercial Zn-Al-Cu (ZA27) alloy was gas atomized and the resulting powder was mixed with an Al2O3 powder, and then hot pressed into cylindrical pellets. Metal powder and powder mixtures were pressed at 230 degrees C, for 45 mm under the pressure of 150 MPa. The compressive strength testing was performed in the temperature range from 20 degrees C to 160 degrees C, with a deformation rate of 2.4 x 10(-3)s(-1). The microstructures and the :fracture surface of the samples were investigated by optical and scanning electron microscopy

Interaction of ns laser with 316L-NiB stainless steel obtained by powder metallurgy – morphological effects and LIBS analysis

Austenitic stainless steel 316L finds a number of applications including filtration technology, nuclear industry, biomedicine, etc. Powder metallurgy (PM) allows obtaining the desired structure of the material, from full density to highly porous one, and PM technology most often comprises pressing and sintering steps. Gravity sintering, applied in this work, i.e. liquid phase sintering where the pressing step is excluded, is enabled by adding small amount of boron or its compound [1]. The addition of NiB lowers the sintering temperature by formation of eutectics (liquid phase), and also enhances mechanical properties (tensile strength, hardness) and corrosion resistance of 316L steel [2]. The aim of this work was to examine the surface behavior of PM-obtained 316L-NiB exposed to conditions of high heat fluxes by employing nanosecond laser pulses (TEA CO2 laser emitting at 10.6 μm, fluence ~14 J/cm2, intensity ~40 MW/cm2), which is reported scarcely in literature [3]. Simultaneously with irradiation in vacuum, plasma formed by laser irradiation above the sample surface was analyzed using LIBS (Laser Induced Breakdown Spectroscopy). Namely, small amount of boron (1 wt.% of NiB contains 83 wt.% of Ni and 17 wt.% of B) is not easily detected in gravity sintered sample and one of the techniques of choice could be the LIBS. For comparison purposes, 316L sample wihout NiB was also examined. Laser-irradiated surfaces were analyzed using SEM connected to EDX device. The damage was superficial, with intense melting in the central part of the irradiated spot, Fig. 1(a). LIBS analysis, Fig. 1(b), has shown successful in detecting the presence of boron in the 316L-NiB stainless steel, with low estimated limit of detection of 32 ppm.IX International School and Conference on Photonics : PHOTONICA2023 : book of abstracts; August 28 - September 1, 2023; Belgrad

Femtosecond laser surface texturing of aisi 1045 steel

Morphological changes, including texturing and production of highly oriented periodical surface structures (LIPSS), on AISI 1045 steel were carried out by femtosecond laser pulses. The surface changes, induced by laser, are highly localized with minimal hydrodynamic effects and without the presence of a debris. The produced LIPSS have the periodicity of 700 nm, and were more prominent in case of triple scanning. Elemental analysis of the surface showed chemical changes, due to formation of oxides and diffusion of carbon from the bulk. These changes are also more obvious in case of triple scanning

Picosecond pulsed laser ablation of silicon single crystal

Silicon-based nanoparticles (SiNPs) attract authors’ attention due its application prospects in a mutual field, from energy storage to bio-imaging. One of the most prominent methods for synthesis of SiNPs is pulsed laser ablation in liquid media (LAL), because it is simple, and it provides the minimum of contamination of the sample produced. Employed pulsed lasers in LAL are ns- and ps-, and the usage of fs- lasers are reported recently, as well. The objects of the LAL analyses are ablated craters on the Si target surface and, predominantly, the ablated material. Here, SiNPs are synthesized by ps- laser (150 ps, 1064 nm) ablation of Si single-crystal plates in de-ionized water. The focus of the work is the impact of the additional continuous wave (CW) laser (532nm) on the properties of the ablated material, i.e. SiNPs produced. The comprehensive analyses were performed, including the SiNPs’ size distribution, agglomeration abilities, aging, chemical properties (amount of oxygen and its distribution within the particles), and photoluminescence (PL) properties of the solution produced. It is demonstrated that PL properties of obtained SiNPs solution are impacted by introducing the CW laser in the ablation process. The peculiarity lies in the fact that such impact depends on both the PL excitation wavelength and the power of the introduced CW laser, which might open the possibility of successful tailoring of SiNPs produced by LAL.SPIG 2022 : 31st Summer School and International Symposium on the Physics of Ionized Gases : Contributed papers and abstracts of invited lectures, topical invited lectures and progress reports; September 5-9,2022, Belgrad

The influence of boron addition on properties of copper-zirconium alloys

Copper-zirconium alloys with high conductivity were produced using powder metallurgy. Two-steps manufacturing process, containing mechanical alloying followed by hot pressing, was applied in achieving improved mechanical and physical properties of Cu-Zr alloy. In this paper, the influence of boron on Cu-Zr alloys properties was studied on Cu-1Zr (wt.%) and Cu-1.1Zr-0.3B (wt.%) systems. Scanning electron microscopy, laser nanoparticle sizer, computed tomography and X-ray diffraction were employed for observation of changes in the microstructure during production steps. More specifically – variations in size of the Cu particles, powder mixtures’ structural parameters, and development of CuZr phase in binary alloy, CuZr phase and ZrB2 particles in ternary alloy were observed. It was shown that presence of boron increases dislocation density in ternary alloy over the mechanical alloying time compared to binary alloy. The results presented in this study show higher hardening effect in Cu-Zr-B alloy compared to Cu-Zr alloy, resulting in stable hardness values during thermomechanical treatment. Further, it can be seen that finely dispersed reinforcing ZrB2 particles in copper matrix does not have significant influence on its conductivity. Moreover, both systems Cu-Zr and Cu-Zr-B exhibit better electrical conductivity after thermomechanical treatment as a result of zirconium reduction in solid solution due to its precipitation.Високо проводне легуре бакра са додатком цирконијума произведене су металургијом праха. У постизању побољшаних механичких и физичких својстава CuZr легуре примењен је двостепени процес производње, који садржи механичко легирање праћено топлим пресовањем. У овом раду проучаван је утицај бора на својства Cu-Zr легура поређењем система Cu-1Zr (теж.%) и Cu-1.1Zr-0.3В (теж.%). Промене у микроструктури током производних корака праћене су помоћу метода: скенирајућа електронска микроскопија, ласерско одређивање величина микро- и наночестица, компјутерска томографија и рендгенска дифракција. Посебно су посматране варијације у величини честица бакра, структурних параметара мешавине праха и развој CuZr фазе у бинарној легури, као и CuZr фазе и ZrВ2 честица у терцијарној легури. Показало се да присуство бора повећава густину дислокација у терцијарној легури током механичког легирања у поређењу са бинарном легуром. Резултати приказани у овој студији показују већи ефекат ојачавања у легури Cu-Zr-B у поређењу са легуром Cu-Zr, што резултира стабилним вредностима тврдоће током термичке обраде. Даље, може се видети да фино дисперговане честице ZrB2 у матрици бакра показују незнатан утицај на њену проводљивост. Такође, оба система Cu-Zr и Cu-Zr-B показују бољу електричну проводљивост након термичке обраде као резултат редукције цирконијума у чврстом раствору услед његовог таложења

Moisture and gamma-ray irradiation effects on the mechanical properties of carbon fibre-reinforced plastics

The effects of gamma-irradiation and moisture absorption on the mechanical properties of carbon fibres-epoxy resin composites were studied. The properties dominated by the matrix and fibre-matrix interface (interlaminar and in-plane shear strength) were measured at room temperature using standard tests. These tests were carried out before and after exposures to gamma irradiation and before and after immersion in water at 80 degrees C during 21 days. The dosage of gamma irradiation was up to 11.7 MGy. The micrographs of surfaces fractured in performed tests were observed on a scanning electron microscope. They were analyzed with consulting the stated effects on mechanical properties and the measured values of the glass transition temperature of tested coupons before and after irradiation and immersion in water. The obtained results show that moisture and irradiation, if they act one after the other, have a significant influence on the degradation of matrix-dominated mechanical properties of the tested carbon-epoxy composite

In-situ Processing of TiB2 Nanoparticle-Reinforced Copper Matrix Composites

In order to produce the composite powder analyzed in this paper, two prealloys were melted and afterwards gas atomized. The obtained TiB2-reinforced copper powder was consolidated by hot isostatic pressing (HIP). Since it is known that a decrease in the size of the reinforcing phase can cause an increase in hardness of composites, the main aim of the experimental work was to obtain as small particles of the dispersed phase as possible by using standard powder metallurgy techniques. Microstructure and microhardness of the as-cast prealloys, as-atomized powder and HIP-ed compacts were examined. The results of these examinations revealed that TiB2 particles about 10 nm in size were in-situ formed and homogenously dispersed in the copper matrix. As a consequence of the TiB2 formation, the microhardness of Cu-TiB2 composite was significantly improved

Microstructure and Properties of Gravity Sintered 316L Stainless Steel Powder with Nickel boride Addition

The present work demonstrates a procedure for synthesis of stainless steel powder by gravity sintering method. As an additive to the basic powder, NiB powder was added in the amount of 0.2 - 1.0 wt.%. Gravity sintering was done in vacuum, at the temperatures of 1100 degrees C - 1250 degrees C, in the course of 3 - 60 min, using ceramic mould. Structural characterization was conducted by XRD, and microstructural analysis by optical and scanning electron microscope (SEM). Mechanical properties were investigated by tensile tests with steel rings. Density and permeability were determined by standard techniques for porous samples. Gravity sintered stainless steel with NiB addition had more superior mechanical and physico-chemical properties compared to stainless steel obtained by standard powder metallurgy procedures - pressing and sintering

The effect of gamma radiation on the properties of activated carbon cloth

Activated carbon cloth dressing is an appropriate wound healing material due to its biocompatibility and adsorption characteristics. The influence of gamma radiation as a sterilization process on the adsorption and mechanical properties of activated carbon cloth was investigated. The specific surface area, micropore volume, pore size distribution, surface chemistry as well as the breaking load of activated carbon cloth before and after gamma radiation were examined. Characterization by nitrogen adsorption showed that the activated carbon cloth was a microporous material with a high specific surface area and micropores smaller than 1 nm. Gamma radiation decreased the specific surface area and micropore volume but increased the pore width. The sterilization process changed the surface chemistry quantitatively, but not qualitatively. In addition, the breaking load decreased but without any influence considering the further application of this material