Abstract:The only effective way to design, produce, analyse and optimise new and existing industrial thermal processes and also laser-based processes is to develop a quantitative knowledge and understanding of the dependence between temperature and time, which allow the desired forming of properties of the final products. The purpose of this paper was the performance of thermoderivative analysis using the UMSA platform of aluminium alloy cooled at chosen rate, for obtaining characteristics used later for laser treatmen… Show more
“…NETZCH Proteus-Thermal Analysis-version 5.2.1 software was used for processing the DTA-TG experiment. The DTA peaks were established on the heating curve along with the transformation enthalpy [28,29,[38][39][40].…”
The continuous development of modern industries rises the necessity for functionally graded materials. This research starts from the consideration that the incorporation of SiC particles in the molten aluminum alloy can be difficult due to the very low wettability of SiC particles. In order to increase their wettability, SiC particles were covered with a layer of metallic copper. The incorporation of SiC particles into the aluminum alloy mass was performed by centrifugal casting. The secondary hypoeutectic Al-Si alloy used in this study was elaborated within the crucible of a resistors heated furnace. The metallic coating of SiC particles, in addition to the effect of increasing their wettability by molten metal, also has a role in preventing the formation of aluminum carbide in case of heating above 700 °C. A great amount of attention was paid to the parameters used during the centrifugal casting process. The results showed that adjusting the proportion of SiC particles within the composite allows us to obtain values of the thermal expansion coefficient within previously established limits. The present work demonstrates that the coating of SiC particles covered with a thin layer of metallic Cu creates the conditions to easily incorporate them into the molten Al mass, thus obtaining FGMs with controlled properties.
“…NETZCH Proteus-Thermal Analysis-version 5.2.1 software was used for processing the DTA-TG experiment. The DTA peaks were established on the heating curve along with the transformation enthalpy [28,29,[38][39][40].…”
The continuous development of modern industries rises the necessity for functionally graded materials. This research starts from the consideration that the incorporation of SiC particles in the molten aluminum alloy can be difficult due to the very low wettability of SiC particles. In order to increase their wettability, SiC particles were covered with a layer of metallic copper. The incorporation of SiC particles into the aluminum alloy mass was performed by centrifugal casting. The secondary hypoeutectic Al-Si alloy used in this study was elaborated within the crucible of a resistors heated furnace. The metallic coating of SiC particles, in addition to the effect of increasing their wettability by molten metal, also has a role in preventing the formation of aluminum carbide in case of heating above 700 °C. A great amount of attention was paid to the parameters used during the centrifugal casting process. The results showed that adjusting the proportion of SiC particles within the composite allows us to obtain values of the thermal expansion coefficient within previously established limits. The present work demonstrates that the coating of SiC particles covered with a thin layer of metallic Cu creates the conditions to easily incorporate them into the molten Al mass, thus obtaining FGMs with controlled properties.
“…Similar precipitates were also reported by other studies for the same aluminum alloy. 29–31 Additionally, it was reported that the hard and solid nano-particles served as the nuclei of β-Si phase and enhanced the resistance to the growth of α-Al phase during the solidification process of nano-composites. 9 Figure 2.OM images of various specimens including: (a) sample 750-0, (b) sample 750-2, (c) sample 750-4, (d) sample 800-0, (e) sample 800-2 and (f) sample 800-4.…”
In this paper, comparative evaluations on the mechanical properties of Al-Si-Cu alloy reinforced by nano-clay mineral particles were carried out. Such nano-composites contained 1 wt% nano-clay particles and were manufactured through the stir casting with various stirring temperatures and times. Mechanical behaviors such as the hardness and compressive strengths, the elastic modulus and wear properties were studied. The microstructural observations were conducted by the optical and the scanning electron microscopy. Field emission scanning electron microscopy (FESEM) images showed that nano-clay particles distributed uniformly in the aluminum matrix for the nano-composite fabricated at 800 ℃ and was stirred for 2 min. Besides, the lower stirring temperature of 750 ℃ caused a degree of clustering with a size of lower than 200 nm in some places. In comparison with the base alloy, an improvement of 5% to 33% in Brinell hardness value observed for various nano-composites. The wear resistance of various nano-composites also increased two to five times regarding the base alloy. The parameter of µ/E. H2 would predict the wear rate for all specimens. It was found that nano-composites fabricated at the temperature of 750 ℃ exhibited the lower porosity content and the higher ultimate compressive strength, and the elastic modulus.
“…The determination of the laser treatment parameters is also important, particularly the laser power, to achieve a high value of layer hardness to protect the new developing material from losing its properties and to make the tool surface more resistant. Furthermore, EDS microanalysis was applied to determine the chemical composition of the created surface layer [15][16][17][18][19][20].…”
Silver alloys are often used for electrical switches in railway transportation. However, a well-known issue with these switches is their relatively short application period due to certain disadvantages of silver alloys, mainly their low hardness and low resistance to abrasive wear, in contrast to their excellent electrical conductivity. Therefore, the main goal of this study was to increase or maintain the hardness of the surface layer in order to extend the life of worn parts without compromising their electrical properties. Instead of ceramic particles, as in other studies, metallic powders were used, which could increase the electrical and/or thermal properties of silver alloys. The following work presents the use of laser processing as a relatively new technique for metal and metal alloy surface processing technology. In particular, a process based on the melting of silver (Ag) with metallic powders, such as chromium (Cr) and nickel (Ni) particles, is presented. The aim was for these powders to create intermetallic phases with a silver matrix in the obtained surface layer, significantly improving the mechanical properties based on the formation of the phases coherent or semi-coherent with the silver matrix. Regarding the original practical implications of this work, it was important to investigate the possibility of applying fibre laser for surface property enhancement. The scientific aim was to describe the changes in microstructure and compounds that occurred in the laser-remelted surface silver layer after Ni and Cr particles were fed into the basic silver material. It was concluded that the surface layer obtained after chromium application was without cracks and defects and had a higher hardness than the untreated material. A three-zone structure was also found in the obtained surface layer: (1) the remelted zone, (2) the heat-affected zone, and (3) the matrix material. The remelting zone revealed a higher hardness compared to the untreated material, reaching 92 HV0.3, which is more than twice the initial hardness value.
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