New Paradigm On The Mechanical Properties of In-Situ Formed By Al/TiB2 and Al/TiB2/Cu MMCs

In the current study, in-situ formed Al/6wt. % TiB2 and Al/6wt. % TiB2/4wt. % Cu Metal Matrix were investigated. Composites were made using the sir casting method, and both composites were compared. The composite is synthesized by combining two precursor salts, Potassium Hexa Fluro Titanate (KBF4) and potassium tetrafluoroborate (K2TiF6), with stoichiometric compositions corresponding to 6 percent by weight of TiB2 particles, with A356 aluminium melt at 820° C, speed 300 rpm, and holding time 30 minutes. Following that, 4wt. % Cu powder was added to the composite melt, which was then poured into the permanent mould. Mechanical properties tests such as tensile strength, hardness, and fracture toughness were carried out in accordance with ASTM guidelines. The mechanical properties of the in-situ formed Al/6wt. % TiB2/4wt. % Cu composite outperform those of the Al/6wt.% TiB2 composite and base metal. Optical micrograph and XRD analysis both confirm the presence of TiB2 and Cu particles.

Microstructure and mechanical properties of dissimilar friction stir welds of AA2014 and AA7075

This work investigates the effect of process parameters on microstructure, mechanical properties, and fracture behavior of friction stir welded high-strength aluminum alloys AA2014-T6 and AA7075-T6. Optical micrograph, tensile property, and hardness profile of each weld were determined for analysis, and the tensile fracture surfaces were studied by scanning electron microscope. Welds microstructure were heterogeneous and displayed structures comprising of both base metals and the onion rings were seen in all welds except for the lowest heat input weld. Grains in the weld nugget zone were more refined on the retreating side than the other side. Asymmetric hardness profile had a distinct softened zone on each side whose location and softening extent varied with the processing parameters. Welding speed had a more significant effect on tensile strength than rotary speed and, drastically decreased the same. Faster welding speed formed microscopic defects and changed the appearance of fractured surfaces from flat to zigzag. The welds underwent ductile and mixed-mode tensile failure on the advancing side. Attainment of optimum combination of process parameters is imperative to yield defect-free stronger dissimilar welds

A novel preform compaction method for fabricating high-performance Y–Ba–Cu–O single-grain bulk superconductor

A novel preform compaction method based on one new type of divisible mould was employed for fabricating single-grain YBCO bulk superconductor, which can complete the preform demoulding process through opening of the mould, rather than pushing the preform out in the regular mould. Thus it has natural superiority on eliminating macro-cracks, which has been proved by the sample surface morphology and the trapped field characterization. In addition, the divisible mould pressed sample exhibits higher levitation force and trapped field properties than the regular mould pressed samples, verifying the potentials of the divisible mould on improving the bulk performance. The optical micrograph results prove the superiority of the divisible mould on eliminating tiny cracks on sample surface. The processing facility and sample reliability brought by the divisible mould should also be emphasized, because the crushing and re-pressing of preform when it presents visible cracks can be omitted and the failed samples with surface cracks will no longer appear. Consequently, the experimental efficiency and stability are both enhanced.

Development and evaluation of a biodegradable packaging from the aryl of the fruit of Hymenaea stigonocarpa Mart. ex Hayne

The fruits of Hymenaea stigonocarpa have a sweet, starchy fibrous structure used as food among wild animals and man in the field. The study aimed to develop and evaluate a biodegradable packaging from the starchy aryl solution of the jatobá fruit (H. stigonocarpa). The amylaceous solution was obtained from the arils of H. stigonocarpa, the biodegradable film was prepared according to the casting technique. The physical-chemical characteristics for thickness (mm), humidity (%), water solubility (%), biodegradability time and transmittance (T%) were evaluated. Morphology by optical micrographic and scanning electron, mathematical modeling in 3D, and for the mechanical parameters of tensile strength, maximum tension, elongation and elasticity module. The results obtained for the biodegradable film were brown yellow color, aroma and homogeneity, thickness 0.27 mm, humidity 12.45%, solubility in water 57.48%, biodegradability of 100%, maximum and minimum transmittance 82.25 and 1.32 (T%), in the optical micrograph small imperfections were observed and in the scanning electron micrograph small cracks. The mathematical modeling in 3D presented a surprising result, which is an important device in the aid of imaging. The mechanical characteristics for maximum tension 3.17 N, rupture stress 1.34 MPa, elongation 2.99% and elasticity with 90.07 MPa presented satisfactory results comparable to other biodegradable films of native starch. Biodegradable packaging from Hymenaea stigonocarpa aryl has great potential for use as a food packaging.

Evaluation of Microstructure, Hardness, and Tensile Properties: A Comparative Study of Stir Cast and Extruded Al7005/Glass-/Fly-Ash-Reinforced Hybrid MMCs

The effect of extrusion ratio and addition of glass and fly ash on microstructural, mechanical properties, and fracture behavior of Al composites is examined. Both the composites and hybrid composites are prepared by the liquid metallurgical technique. Microstructure, extrusion effect on hardness, tensile properties, and fracture are studied using an optical micrograph, hardness tester, Universal Testing Machine, and scanning electron microscope, respectively. Experimental results show that increasing the extrusion ratio leads to a significant enhancement in mechanical properties such as tensile, compression, and yield strength and Young’s modulus, but results in a small reduction of ductility. It has been revealed that the presence of glass and fly ash improve the mechanical properties significantly with a slight reduction in ductility compared to the Al alloy. Fracture behaviour of the base alloy and composites show intergranular ductile and brittle cleavage mode failure as observed by SEM.

Optical Properties of Cholesteric Liquid Crystal Elastomer Film

A series of liquid crystal elastomer (LCE) films (ABC films) were prepared by polymerization of polymethylhydrosiloxane (PMHS), liquid crystal (LC) monomer cholesterol 4-(allyloxy) benzoate (MB) and cross-linking agent 4'-(undec-10-enoyloxy)-[1,1'-biphenyl]-4-yl dodec-11-enoate (MC) . The chemical structures and LC properties of the monomers and polymers were characterised by Fourier Transform Infrared Spectrometer (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), polarized optical micrograph (POM) and X-ray diffractometer (XRD). MB is a cholesteric LC and MC is a smectic LC. The ABC films are cholesteric LCEs. The temperature at which 5% weight loss occurred for the ABC films are around 300 °C. The glass transition temperature of ABC films increases with the increase of LC monomer MB content. The ABC films have a strong absorption around 200-330nm in the ultraviolet (UV) region, and the absorption range does not change with temperature.

TAGUCHI GREY RELATIONAL MULTI-RESPONSE EXPERIMENTAL OPTIMIZATION ON MODIFICATION OF Al-6061 SURFACE USING Si–Cu GREEN COMPACT TOOL IN EDM

This paper presents the surface modification of aluminium-6061 by electric discharge machining (EDM). Si–Cu powder metallurgical green compact tool is used to deposit its material on to the work surface under reverse polarity of EDM. Compact load, current and pulse on-time are selected control parameters. Material deposition rate (MDR), tool wear rate (TWR) and surface roughness ([Formula: see text] are considered as process outputs. Scanning electron microscopic (SEM) analysis and energy dispersive X-ray (EDX) analysis show the presence of tool materials in the deposit of work surface. Olympus optical micrograph shows an average thickness of the deposited layer to be 18.73[Formula: see text][Formula: see text]m. The hardness of the deposited layer is found to be 268[Formula: see text]HV. Analysis of variance (ANOVA) shows the compact load to be the most effective parameter on surface modification followed by pulse on-time and current, respectively.

APPLICATION POTENTIAL OF RESPONSE SURFACE METHOD ON ELECTRO DISCHARGE MACHINING OF AA6061–CENOSPHERE AMCs PREPARED BY COMPOCASTING METHOD

Cenosphere fly ash particles are incorporated into AA6061 alloys with different concentrations ranging from 0[Formula: see text]wt.% to 10[Formula: see text]wt.% using a modified semi-solid metal processing technique. X-ray diffraction patterns were recorded to analyze the morphology of the aluminum-based metal matrix composites (AMCs). The major diffraction peaks of Al, SiO2, Al2O3 and Fe2O3 are distinctly identified which revealed the presence of cenosphere particles and their integrity within the matrix is preserved. The high-resolution optical micrograph identifies the homogeneous distribution and uniform dispersion of the particles. Machinability of the prepared AMCs was investigated by electro discharge machining (EDM) using response surface methodology (RSM). Face-centered CCD of RSM was considered to design the number of experimental runs required. ANOVA was used to explore the influence of selected process parameters and their interactions on the performance characteristics of the systems by developing a second-order quadratic mathematical model for all the responses. Pulse on-time and pulse current were observed to be the most influencing independent variables of EDM system that affect the selected performance measures during spark erosion process. Finally, desirability function approach was employed to optimize the parameters. The optimal processing condition was identified as follows: pulse current: 6 A, pulse on-time: 1010[Formula: see text][Formula: see text]s, percentage of reinforcement: 2% and flushing pressure: 0.2 MPa. Very small percentages of deviation have been observed while comparing with the experimental results obtained for MRR (8.6%), TWR (10.3%) and SR (2.18%).

Tuning the mechanical properties and degradation properties of polydioxanone isothermal annealing

Polydioxanone (PPDO) is synthesized by ring-opening polymerization of p-dioxanone, using stannous octoate as the catalyst. The polarized optical micrograph (POM) shows thes pherulite growth rate of PPDO decreases with an increase in the isothermal crystallization temperature. PPDO is compression-molded into bars, and PPDO bars are subjected to isothermal annealing at a range of temperatures (Ta = 50, 60, 70, 80, 90, and 100 °C), and correspond to three different annealing times (ta = 1h, 2h, 3h). The effect on PPDO is investigated by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). With an increase in Ta and ta, the grain size and the degree of crystallinity also increase. Meanwhile, the tensile strength is significantly improved. The PPDO bars (90 °C, 2 h) reach the maximum crystallinity (57.21%) and the maximum tensile strength (41.1 MPa). Interestingly, the heat treatment process does not result in serious thermal degradation. It is observed that the hydrolytic degradation of the annealed PPDO is delayed to some extent. Thus, annealed PPDO might have potential applications, particularly in the fields of orthopedic fixation and tissue engineering.

Temperature and Time Dependence of the Solvent-Induced Crystallization of Poly(l-lactide)

The role of organic solvents in governing the crystallization and morphology of semi-crystalline poly-l-lactide (PLLA) sheets was systematically investigated. Three different organic solvents; ethyl acetate (EA), o-dichlorobenzene (ODCB), and nitrobenzene (NB), with a solubility parameter analogous to PLLA and with a high capability of swelling, were chosen. It has been witnessed that the degree of crystallization and crystal morphology depends highly on the degree of swelling and evaporation rate of the solvent. Besides, the temperature and time of treatment played a significant role in the crystallization of polymers. The effect of different solvents and curing times are reflected by the measured X-ray diffraction (XRD) peaks and the differences are best shown by the unit cell size. The largest variation is observed along the c-axis, indicating shorter bonds, thus, showing better conformation after NB and ODCB treatment. The percentage of crystallinity calculated using the classical relative crystallinity index of XRD shows closer values to those calculated with differential scanning calorimetry (DSC) data, but a huge variation is observed while using the LeBail deconvolution method. The strong birefringence of polarised optical micrograph (POM) and the crystal morphology of scanning electron micrograph (SEM) also evidenced the orientation of polymer crystallites and increased crystallinity after solvent-supported heat treatment.