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Surface nanocrystallization of Cu-Cr alloy by a high power density continuous laser beam
摘要： A nanostructured surface layer of (cid:1)300 lm thickness was fabricated on Cu-30Cr (wt%) hypereutectic alloy by a continuous laser beam with high power density (1.08 (cid:3) 107 W/cm2). The average grain size of Cr-rich particles was re?ned to (cid:1)40 nm, and the solid solubility limit of Cr in Cu was extended to 1.96 at. %. Experimental results show that the dispersion of nano-sized Cr-rich spheroids in Cu-rich matrix was attributed to the Brownian motion of Cr-rich spheroids, and the high cooling rate (5.75 (cid:3) 106 K/s) during liquid phase separation which inhibits the collisions between Cr-rich spheroids.
关键词： Solidi?cation,Surface nanocrystallization,Microstructure,Cu-Cr alloy,Laser surface melting
更新于2025-11-21 11:18:25
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Effects of Nd:YAG laser surface treatment on tribological properties of cold sprayed Ti-6Al-4V coatings tested against 100Cr6 steel under dry condition
摘要： The surfaces of cold sprayed Ti-6Al-4V (Ti64) coatings were laser irradiated with different laser powers of 50-200 W to study the effects of Nd:YAG laser surface treatment on their tribological properties. The hardness of the laser treated Ti64 coatings became higher with higher laser power due to the more rapid cooling caused by a larger temperature difference between the coating surface and room temperature. The wear of the laser treated Ti64 coatings tested against 100Cr6 steel balls under dry condition at room temperature decreased with increased laser power as a result of their increased surface wear resistance associated with their increased surface hardness. It could be concluded that the laser surface treatment of the cold sprayed Ti64 coatings improved their surface wear resistance compared to that of the untreated Ti64 coatings.
关键词： Ti-6Al-4V,laser power,hardness,wear,laser surface melting,Cold spray
更新于2025-09-23 15:23:52
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Effect of laser surface melting on surface integrity of Ala??4.5Cu composites reinforced with SiC and MoS2
摘要： Two types of composites were prepared with Al?4.5Cu alloy as a matrix using stir casting method. One was reinforced with 10 wt.% of SiC and 2 wt.% of MoS2. The other was reinforced with 10 wt.% of SiC and 4 wt.% of MoS2. Their surfaces were remelted using a CO2 laser beam with an objective to study the influence of laser surface melting (LSM). The topography, microhardness, corrosion resistance and wear resistance of the laser melted surfaces were studied. Overall surface integrity after LSM was compared with as-cast surface. LSM enhanced the microhardness and wear resistance of the surface in each case. Porosity of the laser melted surface was low and corrosion resistance was high. Thus, LSM can be conveniently applied to enhancing the surface integrity of the aluminium composites. However, there is an optimum laser specific energy, around 38 J/m2 in this study, for obtaining the best surface integrity.
关键词： microhardness,aluminium composites,laser surface melting,corrosion resistance,molybdenum disulfide,silicon carbide
更新于2025-09-23 15:21:01
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Effects of laser surface melting on crystallographic texture, microstructure, elastic modulus and hardness of Tia??30Nba??4Sn alloy
摘要： The biocompatibility of orthopedic implants is closely related to their elastic modulus and surface properties. The objective of this study was to determine the effects of cold rolling, recrystallization and laser surface melting (LSM) on the microstructure and mechanical properties of a biphase (α″+β) Ti?30Nb?4Sn alloy. X-ray diffraction (XRD) texture analysis of the cold-rolled substrate revealed the [302]α″//ND texture component, while analysis of the recrystallized substrate showed the [302]α″//ND and [110]α″//ND components. The β-phase texture could not be directly measured by XRD, but the presence of the [111]β//ND texture component was successfully predicted by considering the orientation relationship between the α″ and β phases. Nanoindentation measurements showed that the elastic modulus of the cold-rolled substrate (63 GPa) was lower than that of the recrystallized substrate (74 GPa). Based on the available literature and the results presented here, it is suggested that this difference is caused by the introduction of crystal defects during cold deformation. The combined nanoindentation/EBSD analysis showed that the nanoindentation results are not affected by crystal orientation. LSM of the deformed alloy produced changes in hardness, elastic modulus and crystallographic texture similar to those produced by recrystallization heat treatment, creating a stiffness gradient between surface and substrate.
关键词： laser surface melting,stiffness-graded material,crystallographic texture,cold rolling,titanium alloy,recrystallization
更新于2025-09-23 15:21:01
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Influence of Solidification Conditions on the Microstructure of Laser-Surface-Melted Ductile Cast Iron
摘要： The thermal conditions in the molten pool during the laser surface melting of ductile cast iron EN-GJS-700-2 were estimated by using infrared thermography and thermocouple measurements. The thermal data were then correlated with the microstructure of the melted zone. Additionally, the thermodynamic calculations of a Fe-C-Si alloy system were performed to predict the solidification path of the melted zone. It was found that increasing the cooling rate during solidification of the refined ledeburite eutectic but also suppressed the martensitic transformation. A continuous network of plate-like secondary cementite precipitates and nanometric spherical precipitates of tertiary cementite were observed in regions of primary and eutectic austenite. The solidification of the melted zone terminated with the Liquid → γ-Fe + Fe3C + Fe8Si2C reaction. The hardness of the melted zone was affected by both the fraction of the retained austenite and the morphology of the ledeburite eutectic.
关键词： laser surface melting,ductile cast iron,cooling rate,thermography,tertiary cementite,secondary cementite
更新于2025-09-19 17:13:59
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Surface modification of aluminum alloys with carbon nanotubes by laser surface melting
摘要： Carbon nanotubes (CNTs) could be an excellent reinforcement for metal matrix composites, specifically for composites with aluminum or aluminum alloy matrix. Surface modification to improve hardness and other material properties has been performed by laser surface melting (LSM) process, where the laser beam melts the substrate together with alloying elements or reinforcing phase additives. In this work, Multiwalled CNTs (MWCNTs) were mixed by the electrostatic adsorption process with aluminum powder and the resulting mixed powder was laser melted on the surface of a 6061-aluminum alloy substrate. As a result, a modified substrate surface has been obtained from the Al/MWCNT – substrate co-melting, dilution and re-solidification processes. This modified layer was obtained by different LSM parameters and were characterized by Optical (OM) and Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Field Emission Gun Scanning Electron Microscopy (FEG-SEM), X-Ray Diffraction (XRD) and Raman Spectroscopy (RS). The resulting mechanical behavior was evaluated by Vickers microhardness tests. The results showed that the presence of MWCNT in the aluminum powder improves the laser energy absorption, leading to the formation of a deeper modified layer, with segregation of Si particles homogeneously dispersed and improving the hardness. The formation of Al4C3 was not observed, evidencing that the MWCNTs did not react with the molten Al matrix during the LSM process.
关键词： Laser surface melting,MWCNT,Aluminum alloy
更新于2025-09-16 10:30:52
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Influence of laser surface melting on the properties of MB26 and AZ80 magnesium alloys
摘要： In the present investigation, laser surface melting (LSM) was performed on MB26 and AZ80 magnesium alloys and their surface properties were evaluated. The finite element method (FEM) was used to calculate the resulting temperature during the laser surface melting process. The melted layer average thickness values were about 296 and 190 μm for MB26 and AZ80 alloys, respectively and the variation in the thickness is mainly attributed to the absorption in laser energy. The average grain size of the LSMed MB26 alloy was decreased about 14.5 times and AZ80 had very finer grains than the MB26 along with the fine distribution of second phases. Further, the X-ray diffraction results revealed that the second phase intensities were decreased in both the alloys due to their dispersion. The laser absorption efficiency of MB26 was higher due to the higher plasma attachment during LSM process, thereby has higher melt layer thickness compared to AZ80. The refined microstructure of the melted layer resulted in an increase of micro-hardness up to 110 Hv. Potentiodynamic polarization test results revealed that the corrosion current density (icorr) values of the LSMed MB26 and AZ80 alloys were decreased about 1.8 and 2.5 times, respectively compared to the as-received alloys. A variation in solidification rates of the melt pool due to the alloying elements were attributed to an improvement in the surface and electrochemical properties.
关键词： Corrosion,Polarization,Laser surface melting,Hardness,Magnesium alloys
更新于2025-09-11 14:15:04