L. Błaż

Bio: L. Błaż is an academic researcher from AGH University of Science and Technology. The author has contributed to research in topics: Composite number & Intermetallic. The author has an hindex of 10, co-authored 48 publications receiving 416 citations.

Visco-Plastic Flow of Metal in Dynamic Conditions of Complex Strain Scheme

Abstract: The article applies to a piece of research inspired by the new technology of plastic metal forming called the KOBO method, which uses the mechanical and structural effects of cyclic changes of deformation path. Its commercial usage in the field of large plastic deformations, especially for the production of extruded elements made of hardly deformable metal alloys, naturally generated a question about the optimal conditions for carrying out the process and the criteria for their establishment, i.e., constitutive description. In this context, the work provides data on the force and energy consumption of aluminum and 7075 aluminum alloy extrusion processes, carried out using the KOBO method, and their dependence on the strain rate and temperature. The mechanism of deformation occurring during extrusion by the KOBO method was identified as visco-plastic flow. Characteristic parameters of the process, such as viscosity coefficiency, activation energy, activated volume, and the concentration of point defects generated during the process were evaluated.

Electrodeposition and heat treatment of nickel/silicon carbide composites

Abstract: Electrodeposited Ni/SiC composite coatings were obtained in a Watts-type bath. The effect of fine SiC particles on polarization curves of the cathodic reduction of nickel ions was discussed. The incorporation of the particles into the deposit with respect to current density and SiC concentration in the bath was tested. Cathodic current efficiencies were also calculated. Structure of as-plated and heat-treated Ni/SiC composites were examined by means of metallography observations as well as scanning and transmission electron microscopy methods. Two phase transformations in the temperatures range of 20–700 °C were found. For annealed samples, Ni 2 Si and Ni 3 Si 2 phases were identified. Hardening of the Ni/SiC composites as a function of the particle content in the deposit and annealing temperature was determined by means of the microhardness testing method.

New forging method of bevel gears from structural steel

Abstract: The paper discusses the problem of producing bevel gears in a single operation by complex forging of structural steel on a press with reversibly rotating die (the KOBO method). Within the scheme of investigations there have been carried out measurements and analyses of the force parameters of the process as well as structural observations and mechanical tests of forgings produced at various temperatures. Additionally, the forging process using the KOBO method was compared with the conventional forging giving special attention to the possibility of obtaining products of good quality. It has been found that the KOBO method used in the forging process of structural steel in closed dies enables its plastic shaping under the influence of rather small force of the punch pressure and temperature, considerable lower than that usually applied during conventional forging. In spite of this reduction, the forgings showed correct representation by the die shape, homogeneous structure and good mechanical properties.

Formation of layered Mg/eutectic composite using diffusional processes at the Mg-Al interface

Abstract: A processing technique has been developed to produce a layered magnesium-intermetallic compound light composite from elemental magnesium and aluminium sheets. Structural examination and measurements of transition layer grown at the magnesium-aluminium interface at high annealing temperature were performed. It was found using Mg/Al diffusion couple that solid state diffusion results in development of Al3Mg2 and Mg17Al12 intermetallic compounds, which are separated into two sublayers. The rate of the layer growth substantially increases with the appearance of the liquid phase at the Mg-Al interface. The microstructure resulted from the partial solidification contains an eutectic composed of Mg17Al12 intermetallic compound and solid solution aluminium in magnesium. The structural processes, which transform the magnesium-aluminium interface, can be applied for fabrication of layered magnesium-eutectic composites. Alternately stacked magnesium and aluminium sheets, formed into a packet, were heated until aluminium was exhausted throughout the course of the Mg-Al reaction with the liquid phase contribution. As a result, the composite containing residual magnesium and layers of eutectic mixture (Mg17Al12 and solid solution of aluminium in magnesium) was obtained. Rapid solidification resulted in fine-grained eutectic microstructure development. Using the presented method, composites with required thickness ratio of magnesium and the eutectic layers can be obtained by choosing appropriate thickness ratio of starting magnesium and aluminium sheets.

Anomalies in precipitation hardening process of 7075 aluminum alloy extruded by KOBO method

Abstract: In this paper the influence of the initial conditions of KOBO method extrusion of 7075 aluminum alloy on the structural and mechanical parameters of the products is presented; in particular the paper focuses on how heat treatment affects the course of the post deformation process. Moreover, our fundamental purpose is to attempt to answer the question regarding the role of point defects and their potential usage to control the material's properties. The impetuses to conduct this research were the previous experimental studies of the kinetics of metal extrusion by KOBO method and the results of mechanical properties measurements and microstructural observations of the products. They allowed to formulate the thesis that the point defects generated in metals subjected to large and rapid plastic deformation, forming nano-dimensional clusters, constitute the dominant element of deformation mechanism and structural phenomena that take place both during and after the process. In this paper it is shown that, based on the analysis of the experimental results, the clusters of point defects have a significant thermal stability which remains after extrusion, slows down or completely inhibit the process of diffusion of alloying elements at aging temperature (150 °C). On the other hand, a very fast decay of clusters occurring at high temperature (annealing/solutioning at 470 °C/5 min) creates an excess of point defects, which result in increased diffusion during subsequent aging at 150 °C.

A review of the electrodeposition of metal matrix composite coatings by inclusion of particles in a metal layer: an established and diversifying technology

Abstract: Following a brief overview of their history, which dates back to the 1920s with marked developments during the 1960s and 1970s, the principles of composite coatings, achieved by including particles dispersed in a bath into a growing electrodeposited metal layer, are considered. The principles and role of electroplating compared to other techniques for realising such coatings, are considered. A good quality particle dispersion (often aided by a suitable type and concentration of surfactants) appropriate choice of work-piece shape/geometry and controlled agitation in the bath are seen to be prerequisites for achieving uniform coatings having a well-dispersed particle content by electroplating. Examples are provided to illustrate the influence of bath composition and plating conditions on deposit properties. Engineering applications of included particle composite layers are illustrated by examples of hard ceramic, soft ceramic and polymer inclusion composite coatings from the recent literature. Current trends in the development of composite plated coatings are summarised and their diverse applications are seen to include the use of finely structured (especially nanostructured) and functionally active particles together with hybrid and more complex, e.g. hierarchical, structures for applications ranging from tribology to speciality electronics, magnetic and electrochemical energy conversion materials.

Effect of particle concentration on the structure and tribological properties of submicron particle SiC reinforced Ni metal matrix composite (MMC) coatings produced by electrodeposition

Abstract: In the present work, a nickel sulfate bath containing SiC submicron particles between 100 and 1000 nm was used as the plating electrolyte. The aim of this work is to obtain Ni–SiC metal matrix composites (MMCs) reinforced with submicron particles on steel surfaces with high hardness and wear resistance for using in anti-wear applications such as dies, tools and working parts for automobiles and vehicles. The influence of the SiC content in the electrolyte on particle distribution, microhardness and wear resistance of nano-composite coatings was studied. During the electroplating process, the proper stirring speed was also determined for sub-micron SiC deposition with Ni matrix. The Ni films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The depositions were controlled to obtain a specific thickness (between 50 and 200 μm) and volume fraction of the particles in the matrix (between 0.02 and 0.10). The hardness of the coatings was measured to be 280–571 HV depending on the particle volume in the Ni matrix. The tribological behaviors of the electrodeposited SiC nanocomposite coatings sliding against an M50 steel ball (O 10 mm) were examined on a tribometer. All the friction and wear tests were performed without lubrication at room temperature and in the ambient air (with a relative humidity of 55–65%). The results showed that the wear resistance of the nanocomposites was approximately 2–2.2 times more than those of unreinforced Ni.

Characterization and frictional behavior of nanostructured Ni–W–MoS2 composite coatings

Abstract: Fil: Cardinal, Maria Fernanda. TENARIS Research and Development Centre; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Effect of CTAB concentration in the electrolyte on the tribological properties of nanoparticle SiC reinforced Ni metal matrix composite (MMC) coatings produced by electrodeposition

Abstract: In this study, a nickel sulfate bath containing SiC nanoparticles (between 100 and 1000 nm) was used to obtain hard and wear-resistant nanoparticle reinforced Ni SiC MMCs on steel surfaces for anti-wear applications, such as dies, tools and working parts. The influence of stirring speed and surfactant concentration on particle distribution, microhardness and wear resistance of nano-composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The depositions were controlled to obtain a specific thickness (between 50 and 200 μm) and particle volume fraction in the matrix (between 0.02 and 0.12). The hardness of the resulting coatings was also measured and found to be 280–571 Hv, depending on the particle volume in the Ni matrix. The effects of the surfactant on the zeta potential, co-deposition and distribution of SiC particles in the nickel matrix, as well as the tribological properties of composite coatings, were investigated. The tribological behaviors of the electrodeposited SiC nano composite coatings sliding against M50 steel ball (O 10 mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55–65 %). The results showed that the wear resistance of the nano composites was approximately 2–2.2 times higher than unreinforced Ni deposited material.

Cerium in aluminum alloys

Abstract: Rare-earth metals create unique opportunities in improving properties of aluminum alloys. For over a century, there have been attempts to explore cerium for aluminum alloying, emphasizing advantages it exhibits among rare earths. This review covers laboratory and industrial efforts of applying cerium for a purpose of developing aluminum alloys with superior properties. The binary Al–Ce, ternary Al–Ce–X and higher-order phase systems are reviewed with a focus on the aluminum-rich sections. The role of cerium in forming stable, high-melting-point compounds, improving strength and thermal stability is analyzed along with its function as a grain refiner in the aluminum melt, the eutectic modifier, as de-gasifying and de-slagging agent through its reaction with gas and liquid impurities. In addition to conventional alloys with cerium as a minor and major ingredient also amorphous alloys along with aluminum matrix nanocomposites, exploring cerium oxide as reinforcement, are assessed. The role of cerium in bulk alloying is expanded to surface engineering solutions enhancing aluminum wear and corrosion resistance. Efforts of cerium recovery from parts after end of service life and alloy design for a recycling friendly world are discussed to minimize losses and prevent contamination of material supply chain in modern manufacturing.