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 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.
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 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.
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 250C. 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.
The publication presents the comparison of selected refining methods (gaseous and/or flux) based on mechanical properties of the obtained secondary silumin EN AC-AlSi7Mg0.3 (in accordance to the European Standard PN-EN 1706:2011). The point of reference was a similar primary alloy produced using pure batch materials. The mechanical properties measured in room temperature were used to calculate the materials quality index. The research showed, that properly carried out refinement process of secondary (recycled) alloys can bring their quality indexes close to those of their primary materials. The goal was to assess the efficiency of selected refining methods when applied to the examined group of casting silumins, by measuring the basic mechanical properties (in room temperature) before and after refining. The practical aspect was to choose an effective (ecologically, technologically and economically) method of refining of secondary EN AC-AlSi7Mg0.3 alloy used to cast car rims for JN METAL company in Ostowiec Świętokrzyski (Poland).
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.
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.
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 the research results of the influence of the precipitation hardening on hardness and microstructure of selected Al-Si and Al-Cu alloys obtained as 30 mm ingots in a horizontal continuous casting process. The ingots were heat treated in process of precipitation hardening i.e. supersaturation with subsequent accelerated or natural ageing. Moreover in the range of the study it has been carried out investigations of chemical constitution, microscopic metallographic with use of scanning electron microscope with EDS analysis system, and hardness measurements using the Brinell method. On basis of obtained results it has been concluded that the chemical constitution of the investigated alloys enables to classify them into Al alloys for the plastic deformation as EN AW-AlSi2Mn (alternatively cast alloy EN AC-AlSi2MgTi) and as EN AW-AlCu4MgSi (alternatively cast alloy EN AC-AlCu4MgTi) grades. Moreover in result of applied precipitation hardening has resulted in the precipitation from a supersaturated solid solution of dispersive particles of secondary phases rich in alloying element i.e. Si and Cu respectively. In consequence it has been obtained increase in hardness in case of AlSi2Mn alloy by approximately 30% and in case of AlCu4MgSi alloy by approximately 20% in comparison to the as-cast state of continuous ingots.
This article deal with non-conventional methods to affect the crystallization of Al-alloys by the application of electromagnetic field. The application of electromagnetic field is not technically complicated, it does not require mechanical contact with the melt, and the scale of the crystallization influence is not dependent on the thickness of the casting. Two experimental materials were used: AlSi10MgMn and AlSi8Cu2Mn and two values of electromagnetic induction: B = 0.1 T a B = 0.2 T. The best results for alloy AlSi10MgMn were achieved by application of electromagnetic field with induction B = 0.2 T; during this experiment the best mechanical properties were achieved - the biggest increase of mechanical properties was recorded. The best results for alloy AlSi8Cu2Mn were achieved by combination of electromagnetic field with induction B = 0.1 T and modification by 0.05 wt. % Sr. In this case we don´t recommend to use electromagnetic field with induction B = 0.2 T; because of deposition of coarse grains and decreasing of mechanical properties.
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.
In order for the working status of the aluminum alloyed hydraulic valve body to be controlled in actual conditions, a new friction and wear design device was designed for the cast iron and aluminum alloyed valve bodies comparison under the same conditions. The results displayed that: (1) The oil leakage of the aluminum alloyed hydraulic valve body was higher than the corresponding oil leakage of the iron body during the initial running stage. Besides during a later running stage, the oil leakage of the aluminum alloyed body was lower than corresponding oil leakage of the iron body; (2) The actual oil leakage of different materials consisted of two parts: the foundation leakage that was the leakage of the valve without wear and wear leakage that was caused by the worn valve body; (3) The aluminum alloyed valve could rely on the dust filling furrow and melting mechanism that led the body surface to retain dynamic balance, resulting in the valve leakage preservation at a low level. The aluminum alloy modified valve body can meet the requirements of hydraulic leakage under pressure, possibly constituting this alloy suitable for hydraulic valve body manufacturing.
In order to study the effects of various gating systems on the casting of a complex aluminum alloyed multi-way valve body, both software simulation analysis and optimization were carried out. Following, the aluminum alloyed multi-way valve body was cast to check the pouring of the aluminum alloy valve body. The computer simulation results demonstrated that compared to the single side casting mode, the casting method of both sides of the gating system would reduce the filling of the external gas, while the air contact time would be lower. Adversely, due to the pouring on both sides, the melt cannot reach at the same time, leading to the liquid metal speed into the cavity to differ, which affected the liquid metal filling stability. The riser unreasonable setting led to the solidification time extension, resulting in a high amount of casting defects during solidification. Also, both gating systems led the entire casting inconsequential solidification. To overcome the latter problems, a straight gate was set at the middle pouring and the horizontal gate diversion occurred on both sides of pouring, which could provide better casting results for the aluminum alloyed multi-valve body.
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.
The results of some mechanical properties of four Mg-5Al-xRE-0.4Mn (x = 1 – 5) alloys are presented. The microstructure of experimental alloys consisted of an α-Mg phase and an α+γ semi-divorced eutectic, Al11RE3 phase and an Al10RE2Mn7 intermetallic compound. For gravity casting in metal mould alloys, Brinell hardness, impact strength, tensile and compression properties at ambient temperature were determined. The performed mechanical tests allowed the author to determine the proportional influence of the mass fraction of rare earth elements in the alloys on their tensile strength, yield strength, compression strength and Brinell hardness. The impact strength of the alloys slightly decreases with a rise in the rare earth elements mass fraction.
The paper presents the results of research of impact strength of aluminum alloy EN AC-44200 based composite materials reinforced with alumina particles. The research was carried out applying the materials produced by the pressure infiltration method of ceramic preforms made of Al2O3 particles of 3-6m with the liquid EN AC-44200 Al alloy. The research was aimed at determining the composite resistance to dynamic loads, taking into account the volume of reinforcing particles (from 10 to 40% by volume) at an ambient of 23°C and at elevated temperatures to a maximum of 300°C. The results of this study were referred to the unreinforced matrix EN AC-44200 and to its hardness and tensile strength. Based on microscopic studies, an analysis and description of crack mechanics of the tested materials were performed. Structural analysis of a fracture surface, material structures under the crack surfaces of the matrix and cracking of the reinforcing particles were performed.
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.
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
In this study, rubber seed/shea butter oil was used to formulate core oil. The formulated core oil was characterised. D-optimal mixture design was used for multi response optimisation of the functional properties of rubber seed-shea butter coil oil. Desirable values for some responses might be obtained from a factor combination while for others responses not so desirable values. Through multiple response optimisations, a factor setting that gives the desirable values for all responses was obtained. The selected optimum mixture setting for the formulated core oil is 65.937% Rubber seed and 34.063% Shea butter oil at desirability of 0.924. Under the optimum condition the functional properties of the core oil was found to be 39.57KN/M2, 626.85KN/M2, 36.63KN/M2, 593.906KN/M2, 412.605 and 167.309s for Green Compressive Strength, Dry Compressive Strength, Green Tensile Strength, Dry Tensile Strength, Permeability and Collapsibility respectively. The optimum conditions were validated with less than 0.2% error. The functional properties of the formulated core oil was compared to the functional properties of linseed core oil. It was found that rubber seed-shea butter core oil can be used for producing cores suitable for Aluminium casting.
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.
Aluminum 6082-T6 panels were joined by friction stir welding utilizing a bobbin tool. A thermal simulation of the process was developed based upon machine torque and the temperature dependent yield stress utilizing a slip factor and an assumed coefficient of friction. The torque-based approach was compared to another simulation established on the shear layer methodology (SLM), which does not require the slip factor or coefficient of friction as model inputs. The SLM simulation, however, only models heat generation from the leading edges of the tool. Ultimately, the two approaches yielded matching temperature predictions as both methodologies predicted the same overall total heat generation from the tool. A modified shear layer approach is proposed that adopts the flexibility and convenience of the shear layer method, yet models heat generation from all tool/workpiece interfaces.
The friction and wear properties of 201HT aluminum alloys and the corresponding competitive coupons were tested on an electrohydraulic servo face friction and wear testing machine (MM-U10G). The microstructures of the competitive coupons were investigated by scanning electron microscopy (SEM) and consequently the corresponding friction and wear mechanisms were studied. The results demonstrated that: (1) the best competitive material of friction and wear performance of the 201HT was the 201HTC. (2) the 201HTC modified by carbon following the initial mill for oil storage of the micro-groove to be produced, increased the corresponding lubrication performance reduced the friction coefficient and wear rate effectively. (3) the 201HT-201HTC could obtain both better friction and wear mainly due to the initial process of grinding following the 201HT plastic deformation occurred in the surface and the formation of a series of re-melting welding points, whereas the 201HT material hardness would be similar to the 201HTC material hardness, which led into the competitive material friction and wear performance improvement.
This article describes the influence of thermal and dielectric properties of materials to properties of electrical insulating systems in high voltage electrical equipment. The aim of this experiment is to improve the thermal and dielectric properties of electrical insulating (composite) materials using micro fillers of aluminium oxide Al2O3. Supplement of fillers of aluminium oxide with better thermal conductivity to the electrical insulating systems can be modified to increase their thermal conductivity. Improving the thermal conductivity of electric insulation by addition of micro- or nanofillers and in the same time not adversely affecting the dielectric properties is the objective of the study. Paper is presenting the results measured on prepared samples. Improved thermal conductivity is compared with other dielectric properties as: dissipation factor temperature dependences, resistivity and dielectric spectroscopy. To determine the dielectric insulating properties the following characteristics were measured: tanδ versus temperature from 110°C to 150°C, absorption and resorption currents, volume resistivity. Furthermore, this article describes analysis of moisture and conductivity the material by dielectric spectroscopy.