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.
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.
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.
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.
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.
Very well-known advantages of aluminum alloys, such as low mass, good mechanical properties, corrosion resistance, machining-ability,
high recycling potential and low cost are considered as a driving force for their development, i.e. implementation in new applications as
early as in stage of structural design, as well as in development of new technological solutions. Mechanical and technological properties of
the castings made from the 3xx.x group of alloys depend mainly on correctly performed processes of melting and casting, design of a
mould and cast element, and a possible heat treatment.
The subject-matter of this paper is elaboration of a diagrams and dependencies between parameters of dispersion hardening (temperatures
and times of solutioning and ageing treatments) and mechanical properties obtained after heat treatment of the 356.0 (EN AC AlSi7Mg)
alloy, enabling full control of dispersion hardening process to programming and obtaining a certain technological quality of the alloy in
terms of its mechanical properties after performed heat treatments. Obtained results of the investigations have enabled obtainment of a
dependencies depicting effect of parameters of the solutioning and ageing treatments on the mechanical properties (Rm, A5 and KC impact
strength) of the investigated alloy. Spatial diagrams elaborated on the basis of these dependencies enable us to determine tendencies of
changes of the mechanical properties of the 356.0 alloy in complete analyzed range of temperature and duration of the solutioning and
ageing operations.
Automation of machining operations, being result of mass volume production of components, imposes more restrictive requirements
concerning mechanical properties of starting materials, inclusive of machinability mainly. In stage of preparation of material, the
machinability is influenced by such factors as chemical composition, structure, mechanical properties, plastic working and heat treatment,
as well as a factors present during machining operations, as machining type, cutting parameters, material and geometry of cutting tools,
stiffness of the system: workpiece – machine tool – fixture and cutting tool.
In the paper are presented investigations concerning machinability of the EN AC-AlSi9Cu3(Fe) silumin put to refining, modification and
heat treatment. As the parameter to describe starting condition of the alloy was used its tensile strength Rm. Measurement of the machining
properties of the investigated alloy was performed using a reboring method with measurement of cutting force, cutting torque and cutting
power. It has been determined an effect of the starting condition of the alloy on its machining properties in terms of the cutting power,
being indication of machinability of the investigated alloy. The best machining properties (minimal cutting power - Pc=48,3W) were
obtained for the refined alloy, without heat treatment, for which the tensile strength Rm=250 MPa. The worst machinability (maximal
cutting power Pc=89,0W) was obtained for the alloy after refining, solutioning at temperature 510 o
C for 1,5 hour and aged for 5 hours at
temperature 175 o
C. A further investigations should be connected with selection of optimal parameters of solutioning and ageing
treatments, and with their effect on the starting condition of the alloy in terms of improvement of both mechanical properties of the alloy
and its machining properties, taking into consideration obtained surface roughness.
The results of experimental study of solid state joining of tungsten heavy alloy (THA) with AlMg3Mn alloy are presented. The aim of
these investigations was to study the mechanism of joining two extremely different materials used for military applications. The
continuous rotary friction welding method was used in the experiment. The parameters of friction welding process i.e. friction load and
friction time in whole studies were changed in the range 10 to 30kN and 0,5 to 10s respectively while forging load and time were constant
and equals 50kN and 5s. The results presented here concerns only a small part whole studies which were described elsewhere. These are
focused on the mechanism of joining which can be adhesive or diffusion controlled. The experiment included macro- and microstructure
observations which were supplemented with SEM investigations. The goal of the last one was to reveal the character of fracture surface
after tensile test and to looking for anticipated diffusion of aluminum into THA matrix. The results showed that joining of THA with
AlMg2Mn alloy has mainly adhesive character, although the diffusion cannot be excluded.
Dispersion hardening, as the main heat treatment of silumins having additions of copper and magnesium, results in considerable increase
of tensile strength and hardness, with simultaneous decrease of ductility of the alloy. In the paper is presented an attempt of introduction of
heat treatment operation consisting in homogenizing treatment prior operation of the dispersion hardening, to minimize negative effects of
the T6 heat treatment on plastic properties of hypereutectoidal AlSi17CuNiMg alloy. Tests of the mechanical properties were performed
on a test pieces poured in standardized metal moulds. Parameters of different variants of the heat treatment, i.e. temperature and time of
soaking for individual operations were selected basing on the ATD (Thermal Derivation Analysis) diagram and analysis of literature. The
homogenizing treatment significantly improves ductility of the alloy, resulting in a threefold increase of the elongation and more than
fourfold increase of the impact strength in comparison with initial state of the alloy. Moreover, the hardness and the tensile strength (Rm)
of the alloy decrease considerably. On the other hand, combination of the homogenizing and dispersion hardening enables increase of
elongation with about 40%, and increase of the impact strength with about 25%, comparing with these values after the T6 treatment,
maintaining high hardness and slight increase of the tensile strength, comparing with the alloy after the dispersion hardening
The most important parameters which predetermine mechanical properties of a material in aspects of suitability for castings to machinery components are: tensile strength (Rm), elongation (A5, hardness (HB) and impact strength (KCV). Heat treatment of aluminum alloys is performed to increase mechanical properties of the alloys mainly. The paper comprises a testing work concerning effect of heat treatment process consisting of solution heat treatment and natural ageing on mechanical properties and structure of AlZn10Si7MgCu alloy moulded in metal moulds. Investigated alloy was melted in an electric resistance furnace. Run of crystallization was presented with use of thermal-derivative method (ATD). This method was also implemented to determination of heat treatment temperature ranges of the alloy. Performed investigations have enabled determination of heat treatment parameters’ range, which conditions suitable mechanical properties of the investigated alloy. Further investigations will be connected with determination of optimal parameters of T6 heat treatment of the investigated alloy and their effect on change of structure and mechanical/technological properties of the investigated alloy.
Heat treatment of a casting elements poured from silumins belongs to technological processes aimed mainly at change of their mechanical
properties in solid state, inducing predetermined structural changes, which are based on precipitation processes (structural strengthening of
the material), being a derivative of temperature and duration of solutioning and ageing operations. The subject-matter of this paper is the
issue concerning implementation of a heat treatment process, basing on selection of dispersion hardening parameters to assure
improvement of technological quality in terms of mechanical properties of a clamping element of energy network suspension, poured from
hypoeutectic silumin of the LM25 brand; performed on the basis of experimental research program with use of the ATD method, serving
to determination of temperature range of solutioning and ageing treatments. The heat treatment performed in laboratory conditions on a
component of energy network suspension has enabled increase of the tensile strength Rm and the hardness HB with about 60-70%
comparing to the casting without the heat treatment, when the casting was solutioned at temperature 520 o
C for 1 hour and aged at
temperature 165 o
C during 3 hours.
Aluminum alloys are widely used today in plastic injection molds in the automotive and aerospace industries due to their high strength and weight ratio, good corrosion and fatigue resistance as well as high feed rates. The 5754 aluminum alloy has high corrosion resistance and a structure suitable for cold forming. In this study, an AA 5754-H111 tempered aluminum alloy with the dimensions of 80×80×30 mm was used, and some of the materials were cryogenically heat treated. For the milling operations, ϕ12 mm diameter 76 mm height uncoated as well as TiCN and TiAlN coated end mills were used. Different levels of cutting depth (1.25, 2.0, 2.5 mm), cutting speed (50, 80, 100 m/ min), feed rate (265, 425, 530 m/ min) and machining pattern (concentric, back and forth and inward helical) were used. The number of experiments was reduced from 486 to 54 using the Taguchi L54 orthogonal array. The values obtained at the end of the experiments were evaluated using the signal-to-noise ratio, ANOVA, three-dimensional graphs and the regression method. Based on the result of the verification experiments, the processing accuracy for surface roughness was improved from 3.20 μm to 0.90 μm, with performance increase of 71.88%.
The removal of inclusions is a major challenge prior to the casting process, as they cause a discontinuity in the cast material, thereby lowering its mechanical properties and have a negative impact on the feeding capability and fluidity of the liquid alloys. In order to achieve adequate melt quality for casting, it is important to clean the melts from inclusions, for which there are numerous methods that can be used. In the course of the presented research, the inclusion removal efficiency of rotary degassing coupled with the addition of different fluxes was investigated. The effects of various cleaning fluxes on the inclusion content and the susceptibility to pore formation were compared by the investigation of K-mold samples and the evaluation of Density Index values at different stages of melt preparation. The chemical composition of the applied fluxes was characterized by X-ray powder diffraction, while the melting temperature of the fluxes was evaluated by derivatographic measurements. It was found that only the solute hydrogen content of the liquid metal could be significantly reduced during the melt treatments, however, better inclusion removal efficiency could be achieved with fluxes that have a low melting temperature.
The article presents investigation results of the effect of sand fluidization on the structure and mechanical properties of AlSi9 aluminum alloy. Castings were made by lost foam casting process with sand fluidization in mold at the stages of their solidification and cooling. Sand fluidization was achieved by blowing sand bed with compressed air in a foundry container. The metallographic study was carrying out on samples cut from different sections of the castings. Mechanical properties were determined on specimens made from cast samples. Microstructural analysis showed that sand fluidization increases the cooling rate, as a result, the main microstructural components of the alloy – SDAS, eutectic silicon and needles of the rich-iron phase – decrease. Moreover, in different sections of the casting structure is more uniform. With an increasing the air flow rate, a greater refinement of the structure is observed. Through the use of sand fluidization, the mechanical properties of LFC aluminum alloys increase to the level of gravity die castings.
With the aid of eutectic modification treatment, the precipitation of coarse lamellar eutectic silicon can be suspended during the solidification of aluminum-silicon alloys, thereby the formation of fine-grained, fibrous eutectic Si can be promoted by the addition of small amounts of modifying elements, such as Sr, to the liquid alloy. The effectiveness of this technique is, however, highly dependent on many technological factors, and the degree of modification can be lowered during the various stages of melt preparation due to the oxidation of the Sr-content of the melt. During our research, we investigated the effect of rotary degassing melt treatments coupled with the addition of three different fluxes on the degree of modification of an Al-Si-Mg-Cu casting alloy. It was also studied, that whether additional Sr alloying made before and during the melt treatments can compensate the Sr fading with time. The degree of eutectic modification was characterized by thermal analysis (TA) and the microscopic investigation of TA specimens. It was found, that by using one of the three fluxes, and by adding Sr master alloy rods before the melt treatments, better modification levels could be achieved. It was also found that the measurement of Sr-concentration by optical emission spectroscopy alone cannot be used for controlling the level of eutectic modification.
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