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Modeling and optimization of green-Al 6061 prepared from environmentally source materials
No full textRecent studies are evaluating the use of particulates fabricated from agro-based residues as reinforcement for enhancing the properties of aluminium alloys. This report focuses on the optimization approach and modeling of responses for future prediction, which are absent from the majority of studies involving particle reinforcement of an aluminum matrix. Herein, palm kernel shell ash (PKA) and rice husk ash (RHA) were incorporated with 4 wt% of WSD and used as fillers in the Aluminium-6061 matrix at variable proportions. The response surface approach was utilized in the experiment design, modeling, and outcome optimization. The independent variables are the proportions of PKA and RHA and stir casting temperature. Yield, ultimate tensile, impact strength, elastic modulus, and fracture toughness are examined as response parameters. The results demonstrated that the microstructural property played a significant role in the responses. Incorporating PKA and RHA into the Al-6061 matrix improved the response parameters. Temperatures in the range of 700 and 800 degrees C enhanced the property parameters, even though temperatures within 800 and 900 degrees C caused a decline in response. The dependence of the responses on the pattern between property variables was revealed by surface and contour plots. The development of models for predicting responses. Optimal conditions were reached at 4.03% PKA, 5.12% RHA, and 787 degrees C, with an error of <5% when compared to the forecast responses, thus validating the model
Discrete wavelet transforms analysis of vibration signals for correlating tool wear in diamond turning of additive manufactured Ti-6Al-4V alloy
No full textUltra-precision machining (UPM) of Ti-6Al-4V alloy is widely regarded as a challenging material processing due to excessive tool wear and chemical reactivity of the tool and workpiece. Tool wear has a significant influence on the surface quality and also causes damage to the substrate. Therefore, it is critical to consider the tool condition during diamond turning, especially as precision machining moves toward intelligent systems. Consequently, there is a need for effective ways for in-process tool wear monitoring in UPM. This study aims to monitor the diamond tool wear using time-frequency-based wavelet analysis on vibrational signals acquired during the machining of Additively Manufactured (AM) Ti6Al4V alloy. The analysis employed Daubechies wavelet (db4, level 8) to establish a correlation between the Standard Deviation (SD) of the magnitude in the decomposed vibrational signal obtained from both the fresh and used tools. The analysis revealed that at a feed rate of 1 mm/min, the change in SD is 32.3% whereas at a feed rate of 5 mm/min, the change in SD is 8.4%. Furthermore, the flank wear and microfractures are observed using a scanning electron microscope on the respective flank and rake face of the diamond tool
Steel Plant Wastes as a Resource of Rare Earth Elements and Rare Metals–Characterisation, Resource Estimation, and Economic Assessment
No full textSteel production results in a high magnitude of wastes that are either processed in the plant or sold for by-product generation due to stringent environmental regulations. Approximately 2-4 ton steel slag is generated per ton of crude steel by the steel plant. The major slags being highlighted are blast furnace (BF) slag, Linz-Donawitz (LD) slag, and Laddle-refining (LF) slag. As these slags are obtained primarily from the mixing of iron ore with coke and after a series of high-temperature reactions, metallization of some rare earth elements and rare metals is seen in these slags. This study is aimed to characterize these slag wastes generated from TATA STEEL, India, for the content of strategic and rare earth elements omnipresent by various tools like ICP-MS, SEM, and ED-XRF (equipped with Tornado analysis). BF slag is very rich in Ce (177 ppm), followed by 96 ppm La and 74 ppm Nd, apart from Cs (88 ppm), Sb (118 ppm), Sr (411 ppm), and Zr (337 ppm). Nearly 765 ppm V and 67 ppm Nb are reported in the LD slag. LF slag was analyzed with the presence of 66 ppm Ba, 96 ppm Sb, 48 ppm Nb and 70 ppm Cs. These low tenor raw materials owing to huge tonnage availability can serve as a viable secondary resource for utilization. They would be able to cater the critical metal demand ensuring a zero-waste process as per the economic analysis presented
Structural phase transformation in single-crystal Fe-Cr-Ni alloy during creep deformation using molecular dynamics simulation and regression-based machine learning methodology
No full textManipulation of creep properties and microstructural transformations at different temperatures and applied stresses depicts huge importance for the design and development of various grades of metals and alloys. Therefore, we have considered nano-size face-centered cubic (FCC) single crystal of Fe-Cr-Ni alloy to investigate creep response under a wide range of temperatures and pressure through molecular dynamics (MD) simulation and regression-based machine learning methodologies. From MD simulation, we have found the evolution of multiple rectangular blocks of body-centered cubic (BCC) crystal and layered FCC and HCP crystal during creep deformation under externally applied tensile load. Rectangular blocks and layered crystal structures corroborated with the secondary and tertiary stages of creep curves of Fe-Cr-Ni alloy, respectively. Machine learning methodology provides information to predict the creep properties and correlates data obtained from MD simulations. The results of this investigation will provide an understanding of the creep properties during thermal and mechanical processing, which will help to improve the performance of various grades of steel and other alloys
Evaluation of Microstructure, Mechanical Properties, Wear Resistance and Corrosion Behaviour of Friction Stir‑Processed AZ31B‑H24 Magnesium Alloy
No full textIn the present investigation, friction stir processing has been done on AZ31B-H24 virgin magnesium alloy. Traversing
speed and rotational speed of tool were 20–80 mm/min and 900 rpm, respectively. Microstructure, micro-hardness, wear
resistance and corrosion property of processed alloy were investigated. Friction stir processing produced ultra-fne grain of
2.5–3 μm size at weld nugget. Micro-hardness at weld nugget was in the range of 68–72 VHN and became higher than that
of the virgin alloy (~ 59 VHN). Maximum tensile strength of ~218 MPa, yield strength of ~122 MPa, and total elongation
of~8.1% were obtained for friction stir-processed magnesium alloy, when produced with 80 mm/min tool traversing speed.
Reduction in specifc wear rate for all specimens was more than 99% when compared with virgin alloy. The fnding was
attributed to the change in mechanism of wear from virgin to processed alloy. Micro-cutting/micro-groove formation was
evident during wear for virgin alloy; on the contrary, friction stir-processed specimens exhibited micro-ploughing along with
wide, blunt, and restricted groove formation. Corrosion resistance of same specimens was reduced as compared to virgin
material (~ 0.08 mm/year). Maximum corrosion rate was observed for specimen processed at 80 mm/min tool traversing
speed (~0.24 mm/year). It is noteworthy that overall corrosion resistance of friction stir-processed alloy was enhanced with
decrement in tool traversing speed. At the same time with reference to available literature data, the corrosion resistance of Mg alloy in present experimentation revealed improvement with respect to various Mg alloys, produced through other complementary techniques. The signifcant improvement in wear resistance along with little reduction in corrosion resistance was attributed to the structural modifcation of friction stir-processed Mg allo
Effect of Precipitation Characteristics on Mechanical Properties and Stretch Flangeability of Nano‑Dispersion Strengthened High Strength Ferritic Steel
No full textHot-rolled high strength steel with ferrite matrix and nano-size precipitation is one of the novel advanced ferrous grades at present. This grade of steel, namely NPS800 (Nano-precipitation strengthened 800 grade) fnds application in automobile industry for the manufacture of long member parts of large-capacity vehicles. Apart from the minimum strength level of 800 MPa and ductility over 16%, the steel requires adequate stretch fangeability to prevent a catastrophic failure in service. While the grade achieved the desired tensile strength and ductility as per the stipulated specifcation, there were incidences of erratic stretch fangeability. Detailed microstructural characterization has been carried out to explore the reasons for variations
in stretch fangeability. The study reveals that there is a direct correlation between nature of precipitate distribution and size with stretch fangeability. Pre-dominant interphase-controlled precipitation below~12 nm average size is desirable to obtain desired stretch fangeability. To achieve the typical characteristic of precipitation, Ti/Mo atomic ratio plays an important role
Experimental and Numerical Analysis of Residual Stresses in Similar and Dissimilar Welds of T91 and Super304H Steel Tubes
No full textResidual stress distribution and its magnitude varies across the weldment, contributing to many catastrophic failures. Moreover, it is challenging to reliably measure residual stresses, considering a particular technique. Therefore, the present investigation aims to examine residual stresses in similar (T91-T91) and dissimilar (T91-Super304H) welds before and after post-weld heat treatments (PWHT), using non-destructive methods (sin(2)psi and cos alpha) and SYSWELDS simulations. For a similar weld, the peak tensile residual stresses near to fusion line reached similar to 238 MPa (as per sin(2)psi method) and similar to 258 MPa (as per cos a method), which is similar to 48% of yield stress (520 MPa) of T91 steel. Alternatively, for the case of dissimilar welds, peak tensile residual stresses of similar to 518 MPa and peak compressive residual stresses of similar to 290 MPa were observed at the fusion line of the T91 side and Super304H side, respectively. Dissimilar welds show relatively high residual stresses with significant deviation across weldment due to varying thermal coefficients of expansion/contraction resulting from dissimilar metal joints. Hence, PWHTs were performed to decrease the magnitude of peak residual stresses and their deviation across weldment to enhance the life of welded joints. For instance, the peak tensile residual stresses decreased from similar to 258 to similar to 120 MPa after 775 degrees C-30 min PWHT condition in similar welds. Similarly, for dissimilar welds, post-weld normalizing and tempering (PWNT) at 1050 degrees C-30 min followed by 760 degrees C-60 min condition was found to decrease the residual stresses from similar to 518 to similar to 70 MPa, which is a significant reduction achieved due to austenitizing
An investigation into the effect of various parameters on oil agglomeration process of coal fines
No full textIn the present study, the authors have performed oil agglomeration of coal fines using castor oil and a combination of castor oil and turpentine oil in various proportions. The coal samples were collected from three different mines of Mahanadi Coalfields Limited having high ash content (27-39%). From the post-proximate analysis, it was revealed that in the case of Mine 1 coal, the moisture content was reduced by 83%, for Mine 2 it was 94% and for Mine 3 the moisture reduced by 90% from the initial values. The grade achieved after the oil agglomeration process was G5 grade for Mine 2 coal and G3 grade for Mine 1 & 2 coal. The effect of various parameters such as oil dosage, pulp density, and pH, on yield, ash rejection, and organic matter recovery were studied. The parameter with the highest relative importance was found to be oil dosage (normalized importance of 100%) whereas agitation time and pulp density were found to have normalized relative importance of 74% and 70%, respectively. A non-linear regression model in the form of a quadratic equation has also been proposed for ash rejection (%) based on the independent variables such as pulp density, oil dosage, and agitation time
Pd nanoparticles-decorated borophene nanosheets for intrinsic polarization-induced visible light photocatalysis
No full textThe synthesis of freestanding borophene has remarkable applications in the field of catalysis. Several theoretical studies demonstrated the catalytic properties of borophene-based materials. However, its practical applications remain relatively unexplored. Herein, Pd nanoparticles-decorated freestanding borophene nanosheets (Pd-B) were synthesized successfully, which exhibit photocatalytic properties owing to their polarization-enhanced activity. Density functional theory (DFT) calculations suggest that Pd atoms occupy the alternating hexagonal holes of borophene, resulting in a stable heterostructure, and the electron transfer from Pd to boron creates an intrinsic polarization. In the presence of visible light, Pd-B degrades and subsequently mineralizes the organic pollutants due to efficient separation of photogenerated charge carriers along with the availability of multiple catalytic sites. These findings indicate that metal nanoparticles-decorated borophene-based heterostructures are not only promising candidates for photocatalysis but also can be exploited for other catalytic processes
Impact of Bounding Media on the Attenuation Characteristics of Magnetostrictive Signal Obtained from Pipe Embedded in Soil and Sand
No full textAn indigenously developed magnetostrictive sensing (MsS) device coined "MagStrics" has been used to obtain MsS signals in pipes embedded in sand or soil. The device comprises a rapidly quenched amorphous ribbon prepared in the laboratory, which acts as a transducer as well as the sensing element. In contrast to conventionally used CoFe-based crystalline alloys as sensing elements requiring kiloOersteds of the operating field, the absence of magnetocrystalline anisotropy in the present amorphous ribbons required few Oersteds of the magnetic field. Even at such low magnetic field actuation, MagStrics delivers noticeable MsS signals to distinguish the different attenuation characteristics due to soil or sand as bounding media. In addition to the novel and portable device used with amorphous ribbons as a transducer-sensor element, the investigation involves the analysis of signal intensity ratios, and transmission/reflection co-efficient through the 'Dipstick' technique. Using this technique, the overall attenuation characteristics of MsS signals in sand and soil have been manifested. The experimental attenuation in signal from different bounding media like sand and soil has been confirmed using COMSOL multiphysics simulation to display the impact of bounding media on stress and displacement. The scope of novel characteristics of the device along with its thin transducer-sensor element inducing efficient magneto-mechanical coupling for the detection of defects has been discussed