K. R, Ravi

Mg–Sn–Gd alloys can be considered prospective contenders for creep applications owing to the formation of thermally stable phases. In the present investigation, the solidification behaviour of Mg–Sn–Gd alloys was analysed from cooling curves obtained from thermal analysis within the temperature range of 700–300 °C. The phase evolution as a function of Sn and Gd content was studied by varying the ratio of Sn to Gd (Sn/Gd) at three levels (0.5, 1, and 2) up to a maximum concentration of 3 wt% Sn and Gd, respectively. The phases in the as-cast microstructure were compared with the phases predicted by a commercially available thermodynamic database, and a deviation was observed. The results indicated that the addition of Sn and Gd promoted the formation of a ternary MgSnGd phase. Moreover, the presence of the MgSnGd phase in the microstructure led to significant grain refinement, and its role as a potential grain refiner has been recognized.

The current study focuses on the effect of a post-heat treatment such as solutionizing at 520 °C for 0.5–2.5 h followed by artificial ageing at 165 °C for 2–14 h (T6-like heat treatment) on the microstructure and mechanical properties of selective laser melted (SLM) AlSi10Mg alloy. XRD & DSC analysis shows the Al, Si, and Mg2Si phases present in as-built and heat-treated conditions, which are well correlated with the Thermo-Calc simulation results. The density of as-built AlSi10Mg was 2.66 g/cm3, and it decreased to 2.63 g/cm3 after solutionization, and after artificial ageing, it further decreased to 2.61 g/cm3 due to the lattice strains. As-built sample microstructure consists of fine α-Al cells containing ultra-fine Si particles surrounded by a eutectic Si network due to the high heating and cooling rates involved in SLM processes. After solutionizing, the eutectic Si network structure disappeared by the thermally activated diffusion process forming Si particles in the aluminium matrix. Vickers hardness for as-built condition was 126.6 HV, and after solutionization for 30 min, it decreased to 95.6 HV. However, after subsequent artificial ageing (for 12 h), the hardness value again increased to 119.7 HV. As-built condition showed absorbed impact energy of 8 J and it increased to 17.33 J during solutionization for 0.5 h and again decreased to 9.33 J after subsequent artificial ageing.

The age hardenability of 22 karat gold (Au-5.8wt.%Cu-2.5wt.%Ag) alloyed with Ti at various concentrations (0.5, 0.75, and 1 wt.%) was studied. The addition level of Ti is compensated with Ag to maintain the purity of gold in 22 karat, i.e., 91.75 wt.%. The Ti containing 22 karat gold was prepared by melting Au, Cu, and Ag and adding Ti via Au-6wt.%Ti master alloy. The castings obtained were cold-rolled into thin sheet (90% reduction). Both the cast and cold-rolled sheets were subjected to age hardening treatment (solutionizing and artificial aging). Artificial aging was performed as a function of time at 550 °C to identify the peak aging. At all addition level of Ti, the 22 karat gold responded well to the age hardening treatment. The cold-worked sheet samples showed faster peak aging within 30 min. and higher peak hardness than their cast counterpart. Increasing the Ti concentration increases the peak hardness of both cold-rolled sheet and casting samples. Transmission electron microscopic analysis of the peak aged cold-rolled sheet samples shows uniformly distributed coherent Au4Ti precipitates in Au matrix which contribute to the higher hardness.

The study involves numerically simulating the influence of process parameters on melt pool geometry, cooling rate, and microstructure during laser surfacing of 7075 Al alloy using COMSOL Multiphysics. Both numerical simulations and experiments show that increasing scan speeds at a constant laser power reduces melt pool dimensions and increases cooling rates. At 1000 W laser power and 15 mm/s scan speed, numerically simulated melt pool width, depth, and cooling rate are 3.8 mm, 1 mm, and 1370 K/s, closely matching experimental measurements of 4.2 mm, 1.3 mm, and 1449 K/s. Calculated thermal gradient (G) and solidification rate (R) are correlated with observed solidification morphology. The G/R ratio derived from simulations has higher values at the melt pool's bottom, gradually decreasing toward the top for a given laser power and scan speed. This pattern aligns with optical micrographs showing equiaxed dendrites at the top, and columnar and cellular dendrites in the middle and bottom of the melt pool.

The present study investigates the impact of different heat transfer approaches on the precision of geometry and solidification behavior in additively manufactured thin clad walls. Employing a 2D laser scanner to assess dimensional accuracy, the study demonstrates that thin clad walls produced on a copper base plate with forced air convection exhibit notably superior accuracy compared to those on a mild steel substrate with natural convection. Microstructure analysis unveils distinct characteristics: Thin clad walls printed with natural convection on mild steel display a coarse columnar dendritic structure marked by increasing primary dendrite arm spacing (PDAS) from bottom to top (10.4 ± 0.7 to 14.5 ± 3 µm). In contrast, forced convection leads to a fine cellular and columnar dendritic microstructure with minor PDAS variation (4.6 ± 0.9 to 7.4 ± 1.7 µm) along the entire vertical span.

Solar energy is the most efficient and economic gateway for power generation. The development of solar research and technological innovation, and corresponding decline in the prices of solar power harnessing devices, has paved the way for low-cost energy generation in developing country, India. It is estimated that if at least 10% of the total geographical area are effectively utilized, the available solar energy would be 8 million MW, which is equivalent to ~6000 Mtoe per year (https://www.indiaenergyportal.org/subthemes.php?text=solar ). However, installed photovoltaic systems including the solar panels in desert areas and in the industrial areas are prone to the accretion of dust and dirt particles. This resultant fouling hinders the conversion of incident light into electricity, causing a decline in the energy conversion efficiency up to 50%. To maintain a steady performance of PV panels, the surfaces of which must be cleaned regularly. However, current methods of cleaning are expensive, inefficient, and potentially harmful to the surfaces. With recent progress in nanotechnology research, nanostructured coatings have become multifunctional, efficient, and smart. Particularly, self-cleaning coatings have gained considerable attraction owing to its application in a wide range of fields. In this chapter, a brief review regarding the recent progress of bio-mimic self-cleaning coatings on photovoltaic solar systems is presented. A brief introduction on the types of self-cleaning coatings and their properties, such as wettability, optical transparency, mechanical durability, and environmental durability characteristics, is discussed. A short note on the considerations and developments regarding the fabrication of durable, self-cleaning coatings for photovoltaic systems has been presented.

This study primarily focused on forming pure single-phase FeSb and explored its thermoelectric, mechanical, and electrochemical properties since no reports are available. The FeSb binary alloy has been synthesized through the vacuum melting method, and the phase formation has been confirmed through powder X-ray diffraction (PXRD). The PXRD results show that the synthesized FeSb binary alloy belongs to the hexagonal crystal structure with space group P63/mmc, which coincides with ICSD no. 53971. The pure single phase has been formed by creating a deficiency of 10 % in antimony. The High-Resolution Scanning Electron Microscopy (HR-SEM) and Energy Dispersive X-ray (EDX) analysis have been used to identify the pure single-phase and various elemental components of the hot-pressed pellet of FeSb0.9. The atomic wt.% of iron (Fe) and antimony (Sb) have been identified through EDX spectral analysis. The highest Seebeck coefficient value of −5.4 μV/K is achieved at 497 K, and the lowest electrical conductivity value of 24049 S/m is achieved at 447 K. The hardness of the material is found to be 6.076 GPa, which is much more sufficient for thermoelectric material during industrial handling. The magnetic characteristics of the prepared pure phase FeSb compound have also been measured by Vibrating Scanning Magnetometer (VSM) analysis, which has a weak ferromagnetic nature. Furthermore, three electrodes were employed to study the electrochemical properties, and the alloy has attained the appreciable specific capacitance of 169.5 F/g at 2 A/g.

For thermodynamics reasons, most liquids crystallize when they are cooled below their liquidus temperature. However, crystallization can be obstructed if the cooling occurs faster than some critical cooling rate (102 −1010 K/s). Under such conditions, it is suggested that atoms are forced to ‘freeze-in’ at their positions [1,2] with some local short-range order, due to the finite nature of diffusion kinetics, i.e. the rigid state that is produced maintains the disordered or amorphous structure of the liquid. In this short-communication, using CALPHAD (CALculation of Phase Diagrams), we ask, can the underlying atomic interactions within the liquid state be a valid measurement of a material's glass-forming ability?

The present study deals with the effect of Ultrasonic Treatment (UT) on the synthesis, characterization, and mechanical properties of Al-4.4 wt% Cu alloy reinforced with 2 vol % of Graphite (Grp) particles. Microstructural analysis of composite confirms that the UT enhances the wettability, de-agglomeration, and uniform distribution of Grp particles in the matrix. The micron-sized Grp has been flaked off to submicron particles with increase in aspect ratio from ∼4.7 to ∼6.5 due to ultrasonic cavitation effect. In comparison with monolithic Al-4.4 wt % Cu alloy an overall grain size reduction of 74% has been observed in composite with UT. Grp particles’ reinforcement together with grain refinement has improved the mechanical properties viz. hardness, compressive strength and tensile strength of the synthesized composite with UT. The strengthening mechanisms of the Grp particles in the synthesized composites have been analyzed and discussed.

Al 4043 is commonly used as a filler material for welding of aluminium-based components. In the present research work, Al 4043/xTiB2 (titanium diboride) microcomposites (x = 2, 4, 6, 8 and 10 wt%) are fabricated by dilution of Al 4043/10TiB2 in situ master composites synthesized by salt-melt reaction. To synthesize the nanocomposites, in situ Al 4043/10TiB2 composites are re-melted, diluted and ultrasonic-treated for 5 min. The microstructural analysis revealed that ultrasonic treatment (UT) is beneficial on improving the dispersion and refinement of TiB2 particles. UT of Al 4043/2TiB2 composites reduced the size of TiB2 particles from ~ 1270 to ~ 25 nm. At the same time, the efficiency of UT on agglomerate breakage and particle size reduction decreases with the increase in amount of reinforcement. The hindrance generated by increased amount of reinforcements to ultrasonic wave propagation and allied impairment on cavitation implosion is proposed as the reason for the reduction in efficiency of UT. The mechanical property analysis revealed that UT-assisted size reduction and agglomerate breakage of TiB2 particles significantly increase both hardness and compressive strength of in situ composites. The results revealed that the compressive strength of TiB2-reinforced Al 4043/10TiB2 micro- and nanocomposite increased up to ~ 90 and ~ 150 MPa, respectively. Also, a significant improvement in hardness was observed in the reinforced Al 4043/10TiB2 micro- and nanocomposites by ~ 94% and ~ 98%, respectively, compared to the monolithic alloy.