Magnesium alloys thanks to their high specific strength have an extensive potential of the use in a number of industrial applications. The most important of them is the automobile industry in particular. Here it is possible to use this group of materials for great numbers of parts from elements in the car interior (steering wheels, seats, etc.), through exterior parts (wheels particularly of sporting models), up to driving (engine blocks) and gearbox mechanisms themselves. But the use of these alloys in the engine structure has its limitations as these parts are highly thermally stressed. But the commonly used magnesium alloys show rather fast decrease of strength properties with growing temperature of stressing them. This work is aimed at studying this properties both of alloys commonly used (of the Mg-Al-Zn, Mn type), and of that ones used in industrial manufacture in a limited extent (Mg-Al-Sr). These thermomechanical properties are further on complemented with the microstructure analysis with the aim of checking the metallurgical interventions (an effect of inoculation). From the studied materials the test castings were made from which the test bars for the tensile test were subsequently prepared. This test took place within the temperature range of 20°C – 300°C. Achieved results are summarized in the concluding part of the contribution.
The investigation results of the influence of the reclaim additions on the properties of moulding sands with the GEOPOL geopolymer binder developed by the SAND TEAM Company were presented. Two brands of hardeners were applied in the tested compositions, the first one was developed by the SAND TEAM Company, marked SA72 and the new hardener offered by the KRATOS Company, marked KR72. The main purpose of investigations was to determine the influence of reclaim fractions and the applied hardener on the basic moulding sands properties, such as: bending and tensile strength, permeability and grindability. The unfavourable influence of the reclaim additions into moulding sands on the tested properties as well as an increased hardening rate, were found. Moulding sands, in which the hardener KR72 of the KRATOS Company was used, were less sensitive to the reclaim additions.
The results of investigations of moulding sands with an inorganic binder called GEOPOL, developed by the SAND TEAM Company are presented in the paper. Hardeners of various hardening rates are used for moulding sands with this binder. The main aim of investigations was determination of the influence of the hardening rate of moulding sands with the GEOPOL binder on technological properties of these sands (bending strength, tensile strength, permeability and grindability). In addition, the final strength of moulding sands of the selected compositions was determined by two methods: by splitting strength and shear strength measurements. No essential influence of the hardening rate on such parameters as: permeability, grindability and final strength was found. However, the sand in which the slowest hardener (SA 72) were used, after 1 hour of holding, had the tensile and bending strength practically zero. Thus, the time needed for taking to pieces the mould made of such moulding sand will be 1.5 - 2 hours.
This work presents an influence of cooling rate on crystallization process, structure and mechanical properties of MCMgAl12Zn1 cast magnesium alloy. The experiments were performed using the novel Universal Metallurgical Simulator and Analyzer Platform. The apparatus enabled recording the temperature during refrigerate magnesium alloy with three different cooling rates, i.e. 0.6, 1.2 and 2.4°C/s and calculate a first derivative. Based on first derivative results, nucleation temperature, beginning of nucleation of eutectic and solidus temperature were described. It was fund that the formation temperatures of various thermal parameters, mechanical properties (hardness and ultimate compressive strength) and grain size are shifting with an increasing cooling rate.
During design of the casting products technology, an important issue is a possibility of prediction of mechanical properties resulting from the course of the casting solidification process. Frequently there is a need for relations describing mechanical properties of silumin alloys as a function of phase refinement in a structure and a porosity fraction, and relations describing phase refinement in the structure and the porosity fraction as a function of solidification conditions. The study was conducted on castings of a 22 mm thick plate, made of EN AC-AlSi7Mg0,3 alloy in moulds: of quartz sand, of quartz sand with chill and in permanent moulds. On the basis of cooling curves, values of cooling rate in various casting parts were calculated. The paper also presents results of examination of distance between arms in dendrites of a solid solution α (DASL), precipitations length of silicon in an eutectic (DlSi) and gas-shrinkage porosity (Por) as a function of cooling rate. Statistical relations of DASL, DlSi, Por as a function of cooling rate and statistical multiparameter dependencies describing mechanical properties (tensile strength, yield strength, elongation) of alloy as a function of DASL, DlSi and Por are also presented in the paper.
The results of examinations of the influence of titanium-boron inoculant on the solidification, the microstructure, and the mechanical properties of AlZn20 alloy are presented. The examinations were carried out for specimens cast both of the non-modified and the inoculated alloy. There were assessed changes in the alloy overcooling during the first stage of solidification due to the nuclei-forming influence of the inoculant. The results of quantitative metallographic measurements concerning the refinement of the grain structure of casting produced in sand moulds are presented. The cooling rate sensitivity of the alloy was proved by revealing changes in morphology of the α-phase primary crystals. Differences in mechanical properties resulting from the applied casting method and optional inoculation were evaluated.
The paper presents the method of preparing a composite slurry composed of AlSi11 alloy matrix and 10 vol.% of SiC particles, as well as the method of its high-pressure die casting and the measurement results concerning the tensile strength, the yield point, the elongation and hardness of the obtained composite. Composite castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. There were found the regression equations describing the change of mechanical properties of the examined composite as a function of pressure die casting process parameters. The conclusion gives the analysis and the interpretation of the obtained results.
Ductile iron was quenched using two-variant isothermal transformation. The first treatment variant consisted of one-phase austenitization at a temperature tγ = 830, 860 or 900°C, cooling down to an isothermal transformation temperature of 300 or 400°C and holding from 8 to 64 minutes. The second treatment variant consisted of two-phase austenitization. Cast iron was austenitizied at a temperature tγ = 950°C and cooled down to a supercritical temperature tγ’ = 900, 860 or 830°C. Isothermal transformation was conducted under the same conditions as those applied to the first variant. Ferrite cast iron was quenched isothermally. Basic strength (Rp0.2, Rm) and plastic (A5) properties as well as matrix microstructure and hardness were examined. As a result of heat treatment, the following ADI grades were obtained: EN-GJS-800-8, EN-GJS-1200-2 and EN-GJS-1400-1 in accordance with PN–EN 1564:2000 having plasticity of 1.5÷4 times more than minimum requirements specified in the standard.
Impact of surface and volume modification and double filtration during pouring the moulds on basic mechanical properties and creep resistance of nickel superalloys IN-713C and MAR-247 in conditions of accelerated creep of castings made of post-production scrap of these alloys is evaluated in this paper. The conditions of initiation and propagation of cracks in the specimens were analysed with consideration of stereological properties of material macro- and microstructure. It has been proven that in the conditions of hightemperature creep at 980°C and at stress σ = 150 MPa, creep resistance of superalloy MAR-247 is more than 10 times higher than the creep resistance of IN-713C alloy. In case of IN-713C alloy, the creep resistance negligibly depends on macrograin sizes. But, the macrograin size considerably affects the time to failure of specimens made of alloy MAR-247. Creep resistance of specimens made of coarse grain material was 20% higher than the resistance of fine grain materials.
The paper describes the studies of ternary SnZn9Al1.5 lead-free alloy from the viewpoint of its mechanical behavior as well as microstructure examined by the light and scanning electron microscopy. The authors focused their attention specifically on the fatigue parameters determined by the original modified low-cycle fatigue method (MLCF), which in a quick and economically justified way allows determination of a number of mechanical parameters based on the measurement data coming from one test sample only. The effect of the addition of 1.5% Al to the binary eutectic SnZn9 alloy on its microstructure and the obtained level of mechanical parameters was analyzed. The phases and intermetallic compounds occurring in the alloy were identified based on the chemical analysis carried out in micro-areas by the SEM/EDS technique. It was shown that the addition of 1.5% Al to the binary eutectic SnZn9 alloy resulted in a more favorable microstructure and consequently had a positive effect on the mechanical parameters of the alloy. Based on the conducted research, it was recommended to use a combinatorial method based on the phase quanta theory to quickly evaluate the microstructure and the original MLCF method to determine a number of mechanical parameters.
The article deals with the influence of chemical composition of martensitic stainless steel for castings GXCrNi13-4 (the 1.4317 material) on mechanical properties and structure of as cast steel after heat treatment. Properties of these martensitic stainless steel are heavily influenced by chemical composition and structure of the material after heat treatment. Structure of these steels after quenching is formed with martensite and residual austenite. When tempering the steel the carbon content in martensite is reduced and gently deposited carbides occur. The way of heat treatment has a major impact on structure of martensitic steels with low carbon content and thus on strength, hardness and elongation to fracture of these steels. Chemical composition of the melt has been treated to the desired composition of the lower, middle and upper bounds of the nickel content in the steel within the limits allowed by the standard. Test blocks were gradually cast from the melt. The influence of the nickel equivalent value on structure and properties of the 1.4317 steel was determined from results of mechanical tests.
Magnesium alloys are one of the lightest of all the structural materials. Because of their excellent physical and mechanical properties the alloys have been used more and more often in various branches of industry. They are cast mainly (over 90%) on cold and hot chamber die casting machines. One of the byproducts of casting processes is process scrap which amounts to about 40 to 60% of the total weight of a casting. The process scrap incorporates all the elements of gating systems and fault castings. Proper management of the process scrap is one of the necessities in term of economic and environmental aspects. Most foundries use the process scrap, which involves adding it to a melting furnace, in a haphazard way, without any control of its content in the melt. It can lead to many disadvantageous effects, e.g. the formation of a hard buildup at the bottom of the crucible, which in time makes casting impossible due to the loss of the alloy rheological properties. The research was undertaken to determine the effect of an addition of the process scrap on the mechanical properties of AZ91 and AM50 alloys. It has been ascertained that the addition of a specific amount of process scrap to the melt increases the mechanical properties of the elements cast from AZ91 and AM50 alloys. The increase in the mechanical properties is caused mainly by compounds which can work as nuclei of crystallization and are introduced into the scrap from lubricants and anti-adhesive agents. Furthermore carbon, which was detected in the process scrap by means of SEM examination, is a potent grain modifier in Mg alloys [1-3]. The optimal addition of the process scrap to the melt was determined based on the statistical analysis of the results of studies of the effect of different process scrap additions on the mean grain size and mechanical properties of the cast parts.
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
This paper presents the results of Cr - Ni 18/9 austenitic cast steel modifications by mischmetal. The study was conducted on industrial melts. Cast steel was melted in an electric induction furnace with a capacity of 2000 kg and a basic lining crucible. .The mischmetal was introduced into the ladle during tapping of the cast steel from the furnace. The effectiveness of modification was examined with the carbon content of 0.1% and the presence of δ ferrite in the structure of cast steel stabilized with titanium. The changes in the structure of cast steel and their effect on mechanical properties and intergranular corrosion were studied. It was found that rare earth metals decrease the sulfur content in cast steel and above all, they cause a distinct change in morphology of the δ ferrite and non-metallic inclusions. These changes have improved mechanical properties. R02, Rm, and A5 and toughness increased significantly. There was a great increase of the resistance to intergranular corrosion in the Huey test. The study confirmed the high efficiency of cast steel modification by mischmetal in industrial environments. The final effect of modification depends on the form and manner of placing mischmetal into the liquid metal and the melting technology, ie the degree of deoxidation and desulfurization of the metal in the furnace.
The cast alloys crystallizing in Fe-C-V system are classified as white cast iron, because all the carbon is bound in vanadium carbides. High vanadium cast iron has a very high abrasion resistance due to hard VC vanadium carbides. However, as opposed to ordinary white cast iron, this material can be treated using conventional machining tools. This article contains the results of the group of Fe-C-V alloys of various microstructure which are been tested metallographic, mechanical using an INSTRON machine and machinability with the method of drilling. The study shows that controlling the proper chemical composition can influence on the type and shape of the crystallized matrix and vanadium carbides. This makes it possible to obtain a high-vanadium cast iron with very high wear resistance while maintaining a good workability.
Recent research in the process of aluminum alloy die castings production, which is nowadays deeply implemented into the rapidly growing automobile, shipping and aircraft industries, is aimed at increasing the useful qualitative properties of the die casting in order to obtain its high mechanical properties at acceptable economic cost. Problem of technological factors of high pressure die casting has been a subject of worldwide research (EU, US, Japan, etc.). The final performance properties of die castings are subjected to a large number of technological factors. The main technological factors of high pressure die casting are as follows: plunger pressing speed, specific (increase) pressure, mold temperature as well as alloy temperature. The contribution discusses the impact of the plunger pressing speed and specific (increase) pressure on the mechanical properties of the casting aluminum alloy.
The Mg-RE alloys are attractive, constructional materials, especially for aircraft and automotive industry, thanks to combination of low density, good mechanical properties, also at elevated temperature, and good castability and machinability. Present paper contains results of fatigue resistance test carried out on Elektron 21 magnesium alloy, followed by microstructural and fractographical investigation of material after test. The as-cast material has been heat treated according to two different procedures. The fatigue resistance test has been conducted with 106 cycles of uniaxial, sine wave form stress between 9 MPa and 90 MPa. Fractures of specimens, which ruptured during the test, have been investigated with scanning electron microscope. The microstructure of specimens has been investigated with light microscopy. Detrimental effect of casting defects, as inclusions and porosity, on fatigue resistance has been proved. Also the influence of heat treatment's parameters has been described.