Efforts are being made worldwide to transform road transport to minimise its contribution to greenhouse gas emissions, with a focus on reducing vehicle mass. Lightweight manganese–aluminium steels ...have gained popularity for this purpose due to their low density and combination of strength and plasticity. In this particular study, the solidification process of five lightweight manganese–aluminium steels with different silicon content was investigated. The steels were fabricated by inductive melting in a vacuum and remelted during further thermal analysis. A reference steel composition (Fe-14Mn-10Al-0.2Si-0.8C) was used, and the remaining four steels contained different amounts of silicon (0.5, 1.0, 2.0 and 4.0 mass%). The impact of silicon on solidification was analysed by thermodynamic calculations (CALPHAD method), differential thermal analysis and optical microscopy. The thermodynamic calculations gave good estimates for the liquidus and austenite liquidus temperatures, but higher solidus temperatures than the experimental results. The presence of silicon decreases the density and lowers the solidus and liquidus temperatures, resulting in a prolonged solidification interval. In addition, the spacing of the secondary dendrite arms decreases, except at a silicon concentration of 0.5 mass%, where an increase was observed compared to the reference steel.
The high-temperature oxidation behaviour of three hot-work tool steels, Dievar, H11 and W600, was investigated by simultaneous thermal analysis (STA). Since the steels studied are usually used in the ...heat-treated condition, the high-temperature oxidation was studied in two conditions, the soft-annealed condition and the hardened and tempered condition. Simultaneous thermal analysis was used to study the effects of temperature, chemical composition and thermal condition of the steels on the high-temperature oxidation kinetics. The samples were oxidised for 100 h in air atmosphere in the STA instrument. The temperature range studied was between 400 and 700 °C. The equations describing the high-temperature oxidation kinetics were derived from the STA results. The kinetics can be described by three mathematical functions, namely exponential, parabolic and cubic. However, which function best describes the kinetics depends on the oxidation temperature, chemical composition and thermal state of the steel. Hardened and tempered samples have been shown to oxidise less, resulting in a slower oxidation rate. In addition, steels containing chromium (H11 and Dievar) generally oxidise less than a steel without chromium (W600).
In this research enthalpy balance analysis of the EN AW 5182 aluminium alloys during entire process path of sheet production was made, whereas samples after every step of sheet production process ...path were obtained. Using Thermo-Calc computer program thermodynamic simulation of equilibrium and nonequilibrium solidification was made. Differential scanning calorimetry was made on every sample, whereas the melting characteristic temperatures and the melting enthalpies from the results were obtained. Optical microscopy and scanning electron microscope with energy-dispersive X-ray spectroscopy were used to analyse microstructure and microstructural components. It was found that each step of the process, involving different processing temperatures and deformation, has a significant effect on the reaction/melting enthalpy and cannot be uniquely described. Homogenization reduces and intermediate annealing of the hardened sheet increases the melting enthalpy. Hot rolling has a significant effect on the melting enthalpy, while cold rolling has only a minor effect.
During the die-casting process as well as the hot forming process, the tool is subjected to complex thermal, mechanical, and chemical stresses that can cause various types of damage to different ...parts of the tool. This study was carried out to determine the resistance of various tool steels, i.e., UTOPMO1, HTCS-130, and W600, in molten Al99.7 aluminum alloy at a temperature of 700 °C. The formation kinetics of the interaction layer between the molten aluminum and tool steels was studied using differential scanning calorimetry. Light and field-emission scanning electron microscopy were used to analyze the thickness and nature of the interaction layers, while thermodynamic calculations using the Thermo-Calc software were used to explain the results. The stability of the HTCS-130 and W600 tool steels is better than the stability of the UTOPMO1 tool steel in the molten Al99.7 aluminum. Two interaction layers were formed, which in all cases indicate an intermetallic Al
Fe
layer near the aluminum alloy and an intermetallic Al
Fe
layer near the tool steels, containing small round carbides. It was confirmed that Ni reduces the activity of aluminum in the ferrite matrix and causes a reduction in the thickness of the intermetallic layer.
High pressure die casting is one of the leading casting processes in the modern industry. In the case of high pressure die casting, the melt is in contact with the tool, whereas the chemical ...interaction between the tool, made of hot-work tool steel and the melt occur. In addition, mechanical and heat wear of the tools also occur. For high productivity high resistance to these factors is required. The interaction between molten aluminium alloys Al99.9, Al99.7 and AlSi12 and hot-work tool steel UTOPMO1 was investigated at various experimental temperatures, i.e. 670 °C and 700 °C, whereas the differential scanning calorimetry was used. Optical and scanning electron microscopy were used in order to analyse interaction layer. The result of the interaction is the growth of a reaction layer, which is formed from intermetallic phases from Al–Fe or Al–Fe–Si systems. Reaction layer varies regarding the aluminium alloy and the temperature, to which it is exposed, whereas it is composed of three or four different layers. The thickness of the interaction layer depends only from the temperature, but the number of different layers in the interaction layer depends from the type of the aluminium alloy.
Seventeen new experimental filler metals from eight different alloy systems based on Fe–P–X and Mn–Fe–P–X (X = B, C, Si in various combinations) were created and experimented with. DSC analyses were ...performed to determine the solidus and liquidus temperatures and the melting ranges. Hardness measurements of the alloys were performed in the as-cast state. The alloys contain primary and eutectic intermetallic compounds that make them very hard with average hardness values ranging from 590 HV10 to 876 HV10. The wettability was determined at 1000 °C, 1040 °C and 1080 °C on C22 non-alloy steel and 15CrNiS6 low-alloy steel in Ar 4.6 and 78 vol% H2-22 vol% N2 atmospheres. The results show good wettability at T = 1080 °C in both atmospheres, as the contact angles were mostly ≤30°. Thirteen alloys exhibit very good wettability with average contact angles of ≤15.5°. Nine alloys exhibit excellent wettability with their average contact angles being ≤10°. Wettability improves at higher temperatures. The liquid alloys are reactive to solid steels and form a diffusion joint. Diffusion of P, B, C, and Si from the filler metal into the base material dealloys the composition of the melt near the joint interface. For the same reason, a continuous layer of solid solution forms on the joint interface. When brazing with filler metals rich in carbon, strong carburisation of steels can be observed near the joint.
The aim of our study was to investigate how different thermal conditions affect the transformation temperatures of two hot-work steels with high thermal conductivity. We focused on two conditions: ...soft annealing, and quenching and tempering. Soft annealing results in a ferritic steel matrix with spherical carbides, while quenching and tempering result in a fully hardened and tempered martensitic matrix with secondary and tempering carbides. We analysed samples using a simultaneous thermal analysis (STA) and differential scanning calorimetry (DSC) to determine the transformation temperatures. Controlled heating and cooling allowed us to observe the energy changes associated with the phase transformations. The equilibrium temperatures were calculated using the CALPHAD method. Our study investigated the influence of thermal conditions on different transformation temperatures, including solidus/liquidus temperatures, austenite solid transformation temperatures (A1 and A3), austenite solidification temperatures and bainite and/or martensite transformation temperatures. A DSC analysis was used to quantitatively measure the transformation temperatures and energy absorption during the endothermic processes (austenite solid transformation and melting) and to study the energy release during the exothermic processes (solidification and transformation). The results showed that soft annealing reduced the solidification interval and the solidus temperature, while energy absorption increased during melting. Conversely, quenching and tempering reduced the austenite solid transformation temperatures and energy release during solidification, including δ-ferrite solidification.
The high temperature corrosion at 650°C in the presence of NaCl at atmospheric pressure of AISI 304L, AISI 309, AISI 310S, AISI 314 and AISI 321 austenitic stainless steel was studied. The specimens ...were cyclically heated in the furnace and immersed in a 3.5% aqueous NaCl solution after cooling for 15 min. After each cycle, the change in mass of the samples was measured. The corroded samples were analysed by SEM /EDX, and the corrosion products were analysed by XRD. The chloride ions react with the steel surface to form porous and poorly adherent oxides and metal chlorides. After the mass increase during the first exposure cycles, spalling of the oxides occurred. The high temperature austenitic stainless steels (AISI 309, AISI 310S, AISI 314) showed less mass loss than conventional austenitic steels (AISI 304L). Surprisingly, the stainless steel AISI 321 showed a similar low weight loss after the cyclic test as AISI 309, but a detailed analysis of the exposed surfaces after the test showed a similar corrosion attack as for AISI 304. After the cyclic test at high temperature in the presence of NaCl, a higher concentration of Cr and Ni definitely improves the corrosion resistance under the present conditions, but a certain addition of Si is even more obvious.
Graphical Abstract
Additive manufacturing is a form of powder metallurgy, which means the properties of the initial metal powders (chemical composition, powder morphology and size) impact the final properties of the ...resulting parts. A complete characterization, including thermodynamic effects and the behavior of the metal powders at elevated temperatures, is crucial when planning the manufacturing process. The analysis of the Fe-Mn and Fe-Mn-Ag powder mixtures, made from pure elemental powders, shows a high susceptibility to sintering in the temperature interval from 700 to 1000 °C. Here, numerous changes to the manganese oxides and the αMn to βMn transformation occurred. The problems of mechanically mixed powders, when using selective laser melting, were highlighted by the low flowability, which led to a less controllable process, an uncontrolled arrangement of the powder and a large percentage of burnt manganese. All this was determined from the altered chemical compositions of the produced parts. The impact of the increased manganese content on the decreased probability of the transformation from γ-austenite to ε-martensite was confirmed. The ε-martensite in the microstructure increased the hardness of the material, but at the same time, its magnetic properties reduce the usefulness for medical applications. However, the produced parts had comparable elongations to human bone.
The precipitation microstructure of Al-10Si-0.5 Mg-0.5Mn (wt%) alloys with different Zr additions was investigated. The β-type (i.e. Mg2Si) phase was observed to be dominant in the precipitation ...microstructure. Furthermore, the Q-Al5Cu2Mg8Si6 phase and the π-Al8Mg3FeSi6 phase were also observed to be the dominant thermodynamically stable precipitates at 180 °C. The main strengthening effect can be attributed to the Q-Al5Cu2Mg8Si6 and β-type (i.e. Mg2Si) precipitates due to the fact that the π-Al8Mg3FeSi6 phase is relatively large in size, plate-like in morphology, and low in number density and thereby volume fraction. More importantly, the Zr addition into the Al-Si-Mg-Mn alloys causes the precipitation to start at a lower temperature during ageing, which can be due to the grain refinement effect by Zr addition and thereby enhanced diffusion. This paper provides some insights in precipitation microstructure and thereby shortening the ageing treatment at a relatively low ageing temperature.
•The addition of Zr in the Al-Si-Mg-Mn alloy enhances the precipitation hardening during ageing.•The main precipitated phases that contributed to the peak-ageing hardness are the Q-Al5Cu2Mg8Si6 phase and β-type phase (β”).•The addition of Zr in the Al-Si-Mg-Mn alloy decreases the temperature range of the precipitation for approximately 80 °C.
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