Heating of steel or structural aluminum alloys at a speed of 2 to 50 K/min – characterizing the fire conditions – leads to a reduction in mechanical properties of the analyzed alloys. The limit of proportionality fp, real fy and proof f₀₂ yield limit, breaking strength fu and longitudinal limit of elasticity E decrease as the temperature increases. Quantitative evaluation of the thermal conversion in strengths of structural alloys is published in Eurocodes 3 and 9, in the form of dimensionless graphs depicting reduction coefficients and selected (tabulated) discrete values of mechanical properties. The author’s proposal for an analytical formulation of code curves describing thermal reduction of elasticity modulus and strengths of structural alloys recommended for an application in building structures is presented in this paper.

The paper covers the research on the process of solutionizing of 7075 aluminum alloy in cold tools during the stamping of a high-strength structural element (B-pillar’s base). For technological reasons, in order to obtain high strength parameters of the 7075 alloy, it is necessary to carry out a solutionization process, which allows to obtain dispersion strengthening during ageing process. Properly performed heat treatment of the alloy increases the strength of the material to approx. 600 MPa. The combination of the process of solutionization with simultaneous shaping is aimed at improving and simplifying technological operations of aluminum alloy stamping, shortening the duration of the manufacturing process and reducing production costs. The manufactured lower part of the B-pillar will be used for the verification of the validity of the developed method. During the experiment, a series of stamping tests were carried out, in which the lubricants, pressure and position of the upper and lower blankholders were the variables. The obtained results allow to estimate the influence of the cooling conditions on the strength of the drawpieces obtained after the process of artificial ageing. In order to verify and analyse the results more quickly, a numerical simulation was carried out.

The work presents the results of the experimental research concerning the impact of a heat treatment (toughening) of aluminum bronze CuAl10Fe4Ni4 on its mechanical properties. The conditions of the experiments and selected results are described. A detailed description of the effects of individual heat treatment conditions namely low and high temperature aging is also presented in the work.

Nowadays, aluminum-based composites have been produced by pure alumina (Al2O3) or pure graphene nanoplatelets (GNPs) in aluminum matrix because of the high compressive strength of alumina and the solid lubricant properties of graphene. However, there are no studies on the influence of both alumina and graphene reinforced aluminum composites. In this study, Al-Al2O3 and Al-Al2O3-GNPs composites were reinforced with pure alumina (between 0 and 30 wt.%), pure graphene (0, 0.1, 0.3, 0.5 wt.%), and their hybrid forms (Al2O3-GNPs) by the powder metallurgy method. This method involved ultrasonic dispensing, mixing, filtering, drying, pressing, and sintering processes. From the test results, the micro Vickers hardness of pure aluminum (28.2±1 HV) improved to 51.5±0.8 HV (Al-30Al2O3) and 63.1±1 HV (Al-30Al2O3-0.1GNPs). Similarly, the ultimate compressive strength (UCS) enhanced from 92.4±4 MPa (pure aluminum) to 165±4.5 MPa (Al-30Al2O3) and 188±5 MPa (Al-30Al2O3-0.1GNPs), respectively. In conclusion, the Vickers hardness and ultimate compressive strength of aluminum hybrid composites improved up to 0.1 wt.% graphene content. After 0.1 wt.% graphene content, these mechanical properties decreased because of the clumping of graphene nanoparticles.

In this study, the extrusion characteristics of Al-2Zn-1Cu-0.5Mg-0.5RE alloys at 450, 500, and 550℃ were investigated for the high formability of aluminum alloys. The melt was maintained at 720℃ for 20 minutes, then poured into the mold at 200℃ and hot-extruded with a 12 mm thickness bar at a ratio of 38:1. The average grain size was 175.5, 650.1, and 325.9 μm as the extrusion temperature increased to 450, 500 and 550℃, although the change of the phase fraction was not significant as the extrusion temperature increased. Cube texture increased with the increase of extrusion temperature to 450, 500 and 550℃. As the extrusion temperature increased, the electrical conductivity increased by 47.546, 47.592 and 47.725%IACS, and the tensile strength decreased to 92.6, 87.5, 81.4 MPa. Therefore, the extrusion temperature of Al extrusion specimen was investigated to study microstructure and mechanical properties.

The paper presents the research results of horizontal continuous casting of ingots of aluminium alloy containing 2% wt. silicon (AlSi2).

Together with the casting velocity (velocity of ingot movement) we considered the influence of electromagnetic stirring in the area of the

continuous casting mould on refinement of the ingot’s primary structure and their selected mechanical properties, i.e. tensile strength, yield

strength, hardness and elongation. The effect of primary structure refinement and mechanical properties obtained by electromagnetic

stirring was compared with refinement obtained by using traditional inoculation, which consists in introducing additives, i.e. Ti, B and Sr,

to the metal bath. On the basis of the obtained results we confirmed that inoculation done by electromagnetic stirring in the range of the

continuous casting mould guarantees improved mechanical properties and also decreases the negative influence of casting velocity, thus

increasing the structure of AlSi2 continuous ingots.

The paper presents results of compressive strength investigations of EN AC-44200 based aluminum alloy composite materials reinforced

with aluminum oxide particles at ambient and at temperatures of 100, 200 and 250C. They were manufactured by squeeze casting of the

porous preforms made of α-Al2O3 particles with liquid aluminum alloy EN AC-44200. The composite materials were reinforced with

preforms characterized by the porosities of 90, 80, 70 and 60 vol. %, thus the alumina content in the composite materials was 10, 20, 30

and 40 vol.%. The results of the compressive strength of manufactured materials were presented and basing on the microscopic

observations the effect of the volume content of strengthening alumina particles on the cracking mechanisms during compression at

indicated temperatures were shown and discussed. The highest compressive strength of 470 MPa at ambient temperature showed

composite materials strengthened with 40 vol.% of α-Al2O3 particles.

Improvement of Al-Si alloys properties in scope of classic method is connected with change of Si precipitations morphology through:

using modification of the alloy, maintaining suitable temperature of overheating and pouring process, as well as perfection of heat

treatment methods. Growing requirements of the market make it necessary to search after such procedures, which would quickly deliver

positive results with simultaneous consideration of economic aspects. Presented in the paper shortened heat treatment with soaking of the

alloy at temperature near temperature of solidus could be assumed as the method in the above mentioned understanding of the problem.

Such treatment consists in soaking of the alloy to temperature of solutioning, keeping in such temperature, and next, quick quenching in

water (20 0

C) followed by artificial ageing. Temperature ranges of solutioning and ageing treatments implemented in the adopted testing

plan were based on analysis of recorded curves from the ATD method. Obtained results relate to dependencies and spatial diagrams

describing effect of parameters of the solutioning and ageing treatments on HB hardness of the investigated alloy and change of its

microstructure. Performed shortened heat treatment results in precipitation hardening of the investigated 320.0 alloy, what according to

expectations produces increased hardness of the material.

In paper is presented results of studies concerning ingot of Al with a purity of 99.5% cast with use of stand of horizontal continuous

casting. Mainly together with casting velocity was considered influence of electromagnetic stirrer, which was placed in continuous casting

mould on refinement of ingots structure and theirs usability to plastic deformation. Effect of structure refinement and usability to plastic

deformation obtained by influence of electromagnetic stirring was compared with refinement obtained by use of traditional inoculation,

which consists in introducing of additives i.e. Ti and B to metal bath. On the basis of obtained results was affirmed that inoculation

realized by electromagnetic stirring in range of continuous casting mould guarantees improvement in structure refinement and usability to

rolling of pure Al continuous ingots.

Mechanical properties of aluminum-silicon alloys are defined by condition of alloying components in the structure, i.e. plastic metallic matrix created from solid solution  on the basis of Al, as well as hard and brittle precipitations of silicon. Size and distribution of silicon crystals are the main factors having effect on field of practical applications of such alloys. Registration of crystallization processes of the alloys on stage of their preparation is directly connected with practical implementation of crystallization theory to controlling technological processes, enabling obtainment of suitable structure of the material and determining its usage for specific requirements. An attempt to evaluate correlation between values of characteristic points laying on crystallization curves and recorded with use of developed by the author TVDA method (commonly denominated as ATND method) is presented in the paper together with assessment of hardness of tested alloy. Basing on characteristic points from the TVDA method, hardness of EN AC-AlSi9Mg alloy modified with strontium has been described in the paper in a significant way by the first order polynomial.

Mechanical and technological properties of castings made from 3xx.x alloys depend mainly on properly performed process of melting and

casting, structure of a casting and mould, as well as possible heat treatment. Precipitation processes occurring during the heat treatment of

the silumins containing additives of Cu and/or Mg have effect on improvement of mechanical properties of the material, while choice of

parameters of solutioning and ageing treatments belongs to objectives of research work performed by a number of authors. Shortened heat

treatment, which is presented in the paper assures suitable mechanical properties (Rm), and simultaneously doesn’t cause any increase of

production costs of a given component due to long lasting operations of the solutioning and ageing. Results of the research concern effects

of the solutioning and ageing parameters on the Rm tensile strength presented in form of the second degree polynomial and illustrated in

spatial diagrams. Performed shortened heat treatment results in considerable increase of the Rm tensile strength of the 320.0 alloy as early

as after 1 hour of the solutioning and 2 hours of the ageing performed in suitable.

In paper is presented idea of construction and influence of selected parts of stand of horizontal continuous casting on quality of pure Al and AlSi2

alloy ingots. The main parts of the made stand belong to induction furnace, which is also tundish, water cooled continuous casting mould, system

of recooling, system of continuous ingot drawing and cutting. Mainly was considered influence of electromagnetic stirrer, which was placed

in continuous casting mould on refinement of ingots structure. Effect of structure refinement obtained by influence of electromagnetic stirring was

compared with refinement obtained by use of traditional inoculation, which consists in introducing of additives i.e. Ti and B to metal bath. The

results of studies show possibility of effective refinement of Al and AlSi2 alloy primary structure, only with use of horizontal electromagnetic field

and without necessity of application of inoculants. This method of inoculation is important, because inoculants decrease the degree of purity

and electrical conductivity of pure aluminum and moreover are reason of point cracks formation during rolling of ingots.

Silver coatings have a very high reflection ability. To avoid their darkening from the hydrogen sulphide in the air, a thin layer of heat-resistant colorless lacquer is applied to the coatings. Silver plating is mainly used in jewelery, optics, electronics and electrical engineering. Depending on their application the thickness of the layer may vary from 2 to 24 μm. It can be done in several ways: chemical, electrochemical, contact, etc. The most common way of silver plating is the electrochemical deposition using cyanide and non-cyanide electrolytes. The cyanide electrolytes produce light, fine crystalline, dense and plastic coatings upon silver-plating. Usually silver coatings are applied with copper or nickel intermediate layer. In order to improve the de-oxidation of the aluminum surface new chemical treatment in acid – alkaline solution was applied. Our previous research shows that the presence of diamond nanoparticles in the electrolyte increase the metal deposition. Samples were prepared from electrolyte containing 10 g/l diamond nanoparticles. Their properties were compared to the properties of reference samples. The diamonds were obtained by detonation synthesis. The aim of this study is to obtain electrochemically deposited silver layer with high density, adhesion and electric conductivity on aluminum alloys substrate. The coatingwas directly plated without intermediate layer. Non-cyanide electrolyte composition and electrochemical parameters were determined in order to produce Ag coatings on Al alloy substrate without intermediate layer. The coating is with good adhesion, density and thickness of 14-23 μm.

Activated tungsten inert gas (ATIG) welding has a good depth of penetration (DOP) as compared to the conventional tungsten inert gas (TIG) welding. This paper is mainly focused on ATIG characterization and mechanical behavior of aluminum alloy (AA) 6063-T6 using SiO₂ flux. The characterization of the base material (BM), fusion zone (FZ), heat affected zone (HAZ) and, partially melted zone is carried out using the suitable characterization methods. The weld quality is characterized using ultrasonic-assisted non-destructive evaluation. A-scan result confirms that the ATIG welded samples have more DOP and less bead width as compared to conventional TIG. The recorded tensile strength of ATIG with SiO₂ is better than the conventional TIG welding. The failure mode is ductile for ATIG welding with larger fracture edges and is brittle in the case of conventional TIG welding.

In the past few years, overhead copper transmission lines have been replaced by lightweight aluminum transmission lines to minimize the cost and prevent the sagging of heavier copper transmission lines. High strength aluminum alloys are used as the core of the overhead transmission lines because of the low strength of the conductor line. However, alloying copper with aluminum causes a reduction in electrical conductivity due to the solid solution of each component. Therefore, in this study, the authors attempt to study the effect of various Al/Cu ratios (9:1, 7:3, 5:5) to obtain a high strength Al-Cu alloy without a significant loss in its conductivity through powder metallurgy. Low-temperature extrusion of Al/Cu powder was done at 350ºC to minimize the alloying reactions. The as-extruded microstructure was analyzed and various phases (Cu9Al4, CuAl2) were determined. The tensile strength and electrical conductivity of different mixing ratios of Al and Cu powders were studied. The results suggest that the tensile strength of samples is improved considerably while the conductivity falls slightly but lies within the limits of applications.

Owing to the excellent properties, graphene nanoplatelets (GNPs) show great reinforcing ability to improve the mechanical and tribological properties of Al nanocomposites for many automotive applications. In this work, the GNPs dispersion and reinforcing effect in Al nanocomposite was tested. Solvent dispersion via tip sonication and facile low energy ball milling (tumbling milling) using two milling speeds 200 and 300 rpm were employed to develop GNPs/Al powders. Sintering response of the GNPs/Al sintered samples was gauged at two temperatures (550oC and 620oC). The effects of GNPs content, milling rotation speed and sintering temperature on the density, hardness and wear properties of the nanocomposite were examined. The results indicate that relative density % decreases with increasing GNPs content due to possible reagglomeration. The highest hardness of 35.6% and wear rate of 76.68% is achieved in 0.3 wt.% GNPs/Al nanocomposite processed at 300 rpm and 620oC as compared to pure Al due to uniform dispersion, higher diffusion rate at a higher temperature and effective lubrication effect.

The paper presents selected results of KOBO extrusion process of circular profile ϕ10 mm from aluminum alloy 2099. The main aim of the performed research was to determine the influence of the oscillation frequency of a die on the magnitude of extrusion force. During the process such parameters, as extrusion force, rate of stem and frequency of die oscillation were recorded; oscillating angle of a die was constant and equal ±8°. The die oscillation frequency was changeable in performed tests in the range of 2 ÷ 7 Hz. The obtained results allowed to determine the relation between the maximum extrusion force and the die oscillation frequency during extrusion of aluminum 2099 alloy.

The paper focuses on the experimental analysis of mechanical characteristics of the KOBO process. Basing on the recorded force versus stem position, three stages of KOBO extrusion process were determined, i.e. initialization, stabilization and uniform extrusion. Points separating these stages are two inflection points of recorded diagram. The analysis of each stage was made basing on the results of force diagrams and literature data.