Pristine Specimens Research Articles

Analysis of aging effects on the mechanical and vibration properties of quasi-isotropic basalt fiber-reinforced polymer composites

Eco-friendly natural fiber composites, such as basalt fiber composites, are gaining traction in material science but remain vulnerable to environmental degradation. This study investigates the mechanical and vibrational properties of quasi-isotropic basalt fiber composites subjected to aging in two different environments: ambient (30 ºC) and subzero (-10 ºC), both in distilled water until moisture saturation. Aged specimens absorbed 8.66% and 5.44% moisture in ambient and subzero conditions, respectively. Mechanical testing revealed significant strength reductions in tensile, flexural, impact, and short beam shear tests, with ambient-aged specimens showing the largest decline (up to 31.7% in flexural strength). Vibrational analysis showed reduced natural frequencies, particularly under ambient conditions (27.27%). Sound absorption tests showed that pristine specimens had the highest transmission loss, while moisture-rich ambient-aged specimens had the lowest. SEM analysis confirmed surface degradation, with fiber pull-out and matrix debonding contributing to property loss. This research provides valuable insights into the environmental limitations of basalt fiber composites, emphasizing the need for enhanced durability in eco-friendly materials.

Lightweight, covalent-crosslinked, and ambient-dried polybenzoxazine aerogels for fire resistance and thermal insulation

The rapid advancement of modern industries has imposed demands on thermal insulators that possess not only low thermal conductivities but also multifunctional properties. Polybenzoxazine (PBz) aerogels with several advantages have garnered considerable research interest in recent years. Nevertheless, PBz aerogels acquired from ambient pressure drying still confront the challenge of exhibiting relatively high densities and thermal conductivities. In this study, to enrich the category and propose practical ideas for overcoming the above plight, hexamethylene diisocyanate (HDI) was selected as an additive to prepare lightweight and efficient thermal-insulating PBz aerogels through chemical modification. Compared with the pristine specimens (0.268 g·cm−3, 0.0387 W·m−1·K−1), the HDI-modified PBz aerogels exhibited lower densities (0.237–0.256 g·cm−3) and thermal conductivities (0.0354–0.0370 W·m−1·K−1). Moreover, the introduction of HDI has been demonstrated to not impact their superior intrinsic flame retardance, despite an observed reduction in the residual char yields in the HDI-modified groups. Given these excellent properties, PBz-HDI aerogels are expected to be promising candidates for thermal insulation and fire resistance applications.

Detection and quantification of organosulfur species in the Tagish Lake Meteorite by highly sensitive LC‐MS

AbstractWe analyzed the methanol extracts of six pristine specimens of the Tagish Lake meteorite (TL1, TL4, TL5A, TL6, TL7, and TL10a) and heated and unheated samples of Allende using high‐performance liquid chromatography coupled with high‐resolution, accurate mass–mass spectrometry (HPLC‐HRAM‐MS). All samples contained ppm levels of sulfate and methyl sulfate. The most abundant organosulfur compound in the methanol extracts of the Tagish Lake and Allende samples was methyl sulfate, which was likely formed primarily via an esterification reaction between intrinsic sources of methanol and sulfate. A homologous series of polythionic acids was also observed in the extracts of the Tagish Lake specimens and Allende. The polythionic acids were the most abundant soluble inorganic sulfur species found in the meteorites. Our results were confirmed using retention time, accurate mass, isotope matching, and tandem mass spectrometry (MS/MS). Hydroxymethanesulfonic acid, previously reported in Tagish Lake, was found only in an unheated Allende sample and in low abundance. Here, we propose possible sulfate formation pathways that begin with interstellar dimethyl sulfide, dimethyl disulfide, methyl sulfide, or methanethiol via cold, nebular processes within the interstellar medium and continue via MSA as an intermediary compound ending within planetary bodies with sulfate and methyl sulfate as the final products.

A Comparative Study of Zinc Phosphate and Zirconium-Based Conversion Coatings on Galvannealed Steel: Effect on Corrosion Performance of Electrocoated Systems

The efficacy of an electrocoated system that uses a Zr-based conversion coating was assessed to protect galvannealed (GA) steel. The aim was to determine if a Zr-based system has the potential to replace a system with a traditional zinc phosphate (ZnP) conversion coating, where there are concerns for the environmental and economic sustainability. A comparative study between the two conversion coatings, and a control system with no conversion coating, is presented. Data from AC and DC electrochemistry are utilized with surface analysis investigations of pristine specimens, where scanning electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction have been used to determine the mechanism through which protection, or coating failure, occurs. Further investigations study surface morphology and stability of specimens during immersion in a simulated electrocoat bath, and their effect on the performance of fully electrocoated systems. The corrosion current density (icorr) for bare, ZnP, and Zr-based conversion coated specimens in chloride-containing solution with no electrocoat were found to be approximately 1.90 µA/cm2, 0.30 µA/cm2, and <0.01 µA/cm2, respectively. Rp values of 0.05 kΩ, 4.2 kΩ, and 20.7 kΩ were recorded for bare, ZnP and Zr-based specimens, respectively. The corrosion current density (icorr) for bare, ZnP, and Zr-based conversion coated specimens under chloride-containing conditions with electrocoat were found to be 3.82 µA/cm2, 0.53 µA/cm2, and 0.06 µA/cm2, respectively. |Z| values at 0.01 Hz (|Z|0.01 Hz) were measured, yielding 45.5 GΩ, 47.4 GΩ, and 31.6 GΩ for bare, ZnP, and Zr-based pretreatments respectively, demonstrating excellent barrier properties after electrocoating. Hydrogen evolution reaction (HER) rate values of 3.52 × 10−2 mol·m−2·s−1, 3.12 × 10−2 mol·m−2·s−1, and 2.94 × 10−2 mol·m−2·s−1 were recorded for the bare, ZnP, and Zr-based systems, respectively. This study produced a ranking order of HER rate. This was bare > ZnP > Zr-based. These results suggest that the Zr-based system is less prone to HER, interfering with the electrocoat deposition process. A performance ranking order for pretreated and electrocoated systems was established, where Zr-based > ZnP > control. The level of thickness and roughness provided by the conversion coating is speculated to be the controlling factor for coating performance, where the ZnP conversion coating was found to provide a thicker layer with greater surface coverage beneficial for a uniform electrocoat film build.

Rotational Load Fatigue Performance of a One-Size Implant- Abutment Connection System.

One-size implant-abutment (OSIA) connection systems have been developed for simplicity of clinical use and for a range of implant diameters. The aim of this in vitro study was to investigate the rotational load fatigue performance of different implant diameters and abutment platforms of an OSIA connection system. Narrow, regular and wide diameter implants were tested with Regular Base (RB/WB) abutments of an OSIA system (Straumann. BLX). Wide diameter implants were also tested with Wide Base (WB) abutments. This resulted in 4 test groups (n&#61;5): N-RB/WB (Narrow, 3.5mm, RB/WB abutment), R-RB/WB (Regular, 4.0mm, RB/WB abutment), W-RB/WB (Wide, 5.0mm, RB/WB abutment) and W-WB (Wide, 5.0mm, WB abutment). A rotational load fatigue machine applied a sinusoidally varying stress at an angle of 45o, producing an effective bending moment of 35Ncm at a frequency of 10 Hz in air at 20 oC. The number of cycles to failure was recorded. Results were evaluated using ANOVA. Failed specimens were examined with SEM to evaluate the failure mode. Pristine specimens were sectioned to examine the implant-abutment connection. All specimens in the 3 test groups with RB/WB abutments failed within the range of 558,750 cycles to 4,497,619 cycles, while the W-WB test group reached the upper limit of 5 million cycles without failure. Significant difference was found between abutment platforms (P < .001). There were no significant differences found for implant diameters (P &#61;.857). However, with increasing implant diameter, implant fracture was less common and the location of failure was more coronal and consistently at the level of the implant platform for the abutment, and at the screw neck. For wide diameter implants, WB abutments exhibited a superior fatigue performance than RB/WB abutments, and would be preferred in situations of high mechanical risk. Increasing implant diameter, when used with RB/WB abutments, did not improve fatigue performance due to the one-size prosthetic connection, but failures were less catastrophic, and coronally located, which may be advantageous in managing failures.

Effect of fibre treatment and moisture content on the vibration and acoustic properties of the basalt/hemp hybrid composites

The hybridization reinforcements of composites allow design engineers to enhance the structural and acoustic properties of synthetic fibre-reinforced materials. Natural fibres are considered to have higher potential for replacing synthetic fibres in the composite industry. The present study aims to develop hybrid composite materials for sound insulation applications in the automotive industry. The hybrid composites were developed by reinforcing Basalt and Hemp fibres with Epoxy using vacuum bagging technique and cured under ambient conditions. Vibration and acoustic experiments were carried out on pristine and aged BHU (Basalt-Hemp-Untreated) and BHT (Basalt-Hemp-Treated) specimens. The fibre treatment and moisture gain influenced the natural frequency and stiffness of the hybrid composites. With the fibre treatment, the natural frequency of the specimens was enhanced by 12.8%. With ageing of both BHU and BHT, specimens showed a reduction in the natural frequency by 16.4% and 23% respectively. Moisture ingression into the composites reduced the stiffness and improved the damping factor of the structure. The aged BHU and BHT showed better acoustic performance compared to the pristine specimens.

Real-Time Observation of Nanoscale Kink Band Mediated Plasticity in Ion-Irradiated Graphite: An In Situ TEM Study.

Graphite IG-110 is a synthetic polycrystalline material used as a neutron moderator in reactors. Graphite is inherently brittle and is known to exhibit a further increase in brittleness due to radiation damage at room temperature. To understand the irradiation effects on pre-existing defects and their overall influence on external load, micropillar compression tests were performed using in situ nanoindentation in the Transmission Electron Microscopy (TEM) for both pristine and ion-irradiated samples. While pristine specimens showed brittle and subsequent catastrophic failure, the 2.8 MeV Au2+ ion (fluence of 4.378 × 1014 cm-2) irradiated specimens sustained extensive plasticity at room temperature without failure. In situ TEM characterization showed nucleation of nanoscale kink band structures at numerous sites, where the localized plasticity appeared to close the defects and cracks while allowing large average strain. We propose that compressive mechanical stress due to dimensional change during ion irradiation transforms buckled basal layers in graphite into kink bands. The externally applied load during the micropillar tests proliferates the nucleation and motion of kink bands to accommodate the large plastic strain. The inherent non-uniformity of graphite microstructure promotes such strain localization, making kink bands the predominant mechanism behind unprecedented toughness in an otherwise brittle material.

Comparison of different failure criteria in numerical modeling of electron beam cured polymer nanocomposites

In recent times, fibre reinforced polymer (FRP) composites have overtaken the huge market in the world replacing the old conventional materials due to its significant properties. The experimental work conducted to gather the mechanical properties takes alot of time as FRP composites comprises of various geometrical parameters. Therefore, to reduce the experimental encumbrance, the current work is focused on the numerical analysis using different failure criteria, to examine the bearing response of electron beam cured carbon fibre/epoxy (CF/E) composites joint and to get a suitable numerical model. In order to identify the failure of carbon-fibre/polymer composites joints, this work coupled progressive damage analysis (PDA) with the most appropriate failure criteria, namely the Hashin, Tsai-Wu and Maximum stress criteria. Results show that Hashin criterion gave the best suited bearing response predictions. Hashin criterion predicted the maximum bearing capacity in pristine joint specimens, in between 11 and 17% for greater values of W/D and E/D ratios. In multiwalled carbon nanotubes (MWCNTs) added joint specimens, the predicted values by Hashin criterion is in between 14 and 20%.

Fatigue Studies of Welded Stainless Steel 304L: Effect of Manufacturability and Weld Type, Choice of Fatigue Model, and Comparison to Pristine Material

Abstract This study investigates fatigue life and fracture in welded stainless steel 304L (SS 304L) resulting from load-controlled fatigue. This was done for specimens from two welding manufacturers. Mechanical testing was carried out using a MTS test frame in uniaxial tension. Specimens fabricated in 3 weld configurations (butt, lap, butt-with-backer) were cycled at stress ratio R = 0.1, frequency f = 5 Hz, and experienced varying mean tensile stress. A comparison of the fatigue life of welded and unwelded (or pristine) specimens determined that the fatigue life of welded specimens is considerably shorter. The microstructure in the parent material (PM), heat affected (HAZ) and fusion zones (FZ) was analyzed using SEM, and results suggest that, for a limited number of specimens (backer welds), fracture in the (FZ) was primarily the result of Zener-Stroh cracks. Most welded specimens fractured at the weld-HAZ interface (weld toe), and we postulate that stress concentrations primarily due to abrupt geometrical change at the weld interface led to crack initiation there. Additional stress concentrations at welding induced defects (resulting from high temperature) such as second phase particles, fatigue induced defects, and pre-existing impurities are responsible for crack initiation, crack growth, and eventual fracture. Comparison of unwelded and welded SN curve data using numerical curve fitting methods reveal that the fatigue life of pristine SS 304L follows the expected sigmoid shape found in literature (specifically the Chandran fatigue model), while that of welded SS 304L deviates considerably in low cycle fatigue (LCF) and follows the Basquin power law equation.

Experimental and computational meso-scale investigation on the deformation and failure behaviors of plain woven SiC/SiC with intrinsic and manufactured defect

For plain woven SiC/SiC composites used in aerospace thermal-structural applications, not only the pristine material properties but the open-hole performance are of critical concern for the components in service. This study investigated the influence of intrinsic pores induced during SiC matrix preparation and manufactured holes on the macro mechanical properties of plain woven SiC/SiC through experimental and numerical methods. Tensile tests at room temperature were conducted on SiC/SiC specimens with different hole apertures and configurations, and the digital image correlation (DIC) method was employed for full-field strain measurement. Moreover, micro-computed tomography (μ-CT) was utilized to characterize the internal microstructure, original defects, and failure fractures. Based on the reconstructed mesoscale model, the tensile strength and failure mechanisms of pristine and open-hole specimens were predicted and analyzed, with the models validated against the experimental results. The results showed that the inter-tow defects play an important role on the deformation and failure of pristine SiC/SiC specimens during tensile loading. The notch strength results indicated that SiC/SiC exhibits weak notch sensitivity, and the local mesoscopic deformation of the notch is affected by the combination of macroscopic stress gradients and mesoscopic structures. The mesoscale simulation results showed that the position of the hole has a significant impact on the strength of the single layer SiC/SiC composite. The more the notch invades the warp, the greater the decrease in load-bearing capacity, and the relative position of the weft mainly determines the crack propagation path. The failure mode in the simulation results is consistent with the experimental findings, indicating that the simulation model, which considers the weave architecture, can better explain the notch failure behavior of Ceramic Matrix Composites (CMCs).

Intrinsically self-healing ethylene-anisylpropylene copolymer as a candidate material for innovative electrical insulation layers

A novel ethylene-anisylpropylene copolymer was tested as a candidate material for intrinsically self-healing electrical insulation layers. In addition to the thermal and mechanical properties, the dielectric properties were studied before and after induced mechanical and electrical damage to the specimens. The material was tested according to the standards for electrical insulating materials, which require a detailed characterization of the dielectric properties. Nonstandardized tests of self-healing were also included in the testing. The results revealed that the tested material exhibited excellent dielectric parameters and reasonable thermal and mechanical properties. The self-healing tests of the material revealed a 38 % efficiency for recovery of the mechanical properties after the first damage, and this remained almost unchanged after the second and third damage. The first initial results also indicated that the material recovered, to some extent, its electrical insulation properties even after electrical breakdown. By comparing the dielectric strength of the pristine and self-healed specimens, a promising self-healing efficiency of 63 % was determined.

Effect of ageing conditions on the low velocity impact behavior and damage characteristics of aramid-basalt/epoxy hybrid interply composites

Polymer composites reinforced with aramid and basalt fibres are widely used in aviation, automobile, marine and civil structural components. In these applications, composites are often exposed to different environments involving temperature and humidity, which leads to the deterioration of mechanical properties and service life of the structure. This study aimed at investigating the influence of different ageing conditions on the low velocity impact (LVI) performance of 2-D aramid-basalt/epoxy interply composites. Compression molding method of fabrication was employed to prepare the hybrid laminates. LVI coupons were made as per the ASTM D3763 standard and aged in distilled water medium at three different temperatures namely, ambient condition (25 ℃), sub-zero condition (−10 ℃), and humid condition (40 ℃ and 60% relative humidity) until the specimens attain moisture saturation. After ageing, specimens were put through low velocity impact testing at two different impact energies of 10 J and 15 J and results were compared with the pristine specimens. Ultrasonic C-Scan and Scanning Electron Microscopy (SEM) were utilized to analyse the delamination due to impact and micro structural assessment of the pristine and aged specimens. Studies revealed that, specimens aged under sub-zero conditions showed better impact response compared to all other ageing conditions. Furthermore, fibre rupture, matrix decomposition, weakened fibre–matrix interface bonding and delamination were the major damages observed in aged specimens.

Water uptake on lightning strike damage of carbon fiber reinforced composites with surface protections

The effect was examined of water uptake on the lightning strike (LS) damage of carbon fiber reinforced composites (CFRCs) and surface-protected CFRCs. First, water absorption (WA) experiments on CFRC, CFRC adhered to a copper mesh (CFRC-Cu) and CFRC bonded with an aluminum coating (CFRC-Al) were performed to obtain specimens with various water contents. Then, simulated LS tests were carried out on the specimens to investigate the LS damage mechanism. The experimental results showed that the LS damage level of the pristine CFRC specimens increased with the addition of water content, primarily due to the decreased glass transition temperature of the matrix, the increased longitudinal electrical conductivity and the gas explosion after WA. In terms of the CFRC-Cu specimens, the decreased interfacial properties between the copper mesh and the insulated adhesive layer are attributed to the aggravated LS damage area of the copper mesh, whereas the gas explosion is the key factor contributing to the increased damage in the CFRC-Al specimens. In addition, an increase in the adhesive layer thickness intensified the LS damage in the CFRC-Cu specimens but reduced the damage in the CFRC-Al specimens after WA.

3D conductive monolithic carbons from pyrolyzed bamboo for microfluidic self-heating system

Bamboo, like wood, is a promising natural template for biobased devices that takes advantage of its hierarchical architecture, microarray channels, anisotropic mechanical and electrical properties. Herein we report a low heat thermal treatment (HTT, 700-1000 °C) of natural bamboo specimens to obtain bamboo-based graphitic devices with thermoelectric and electrochemical properties. The preservation of the highly anisotropic architecture of three-dimensional carbon material (3D-CM) allowed adding specific thermoelectric and electrochemical properties depending on the HTT of the pristine specimens. High electric conductivity (σ, 839 S/m) was observed at 1000 °C showing a remarkable potential application as a bamboo-based working electrode. The bamboo annealed to 700 °C showed higher resistivity (ρ, 0.15 Ω m, and σ, 6.6 S/m), thermal conductivity (1.77 W/m K), and thermal heating rate (1.0 °C/s). The pyrolyzed biomass (B-700) was used as a 3D microfluidic heater to heat polar solvents (H2O and ethylene glycol) in flow mode up to their boiling points. A 2D carbon hotplate heater was built-up to warm solvent in batch mode. A complete chemical and physical characterization of the samples allowed us to determine structural and chemical compositions, cellulose crystalline structure phase transition to graphitic/turbostratic carbon, thermal and electrical conductivity of unprecedented bambootronics bio-devices.

High versus low energy ion irradiation impact on functional properties of PLD-grown alumina coatings

It is well known that ion irradiation can be successfully used to reproduce microstructural features triggered by neutron irradiation. Even though the irradiation process brings many benefits, it is also associated with several drawbacks. For example, the penetration depth of the ion in the material is very limited. This is particularly important for energies below MeV, ultimately reducing the number of available irradiation facilities. In addition to that, extracting information exclusively from the modified volume may be challenging. Therefore, extreme caution must be taken when interpreting obtained data. Our work aims to compare the findings of nanomechanical studies already conducted separately on thin amorphous ceramic coatings irradiated with ions of different energies, hence layers of different thicknesses. In this work, we show that in some instances, the 10% rule may be obeyed. In order to prove our finding, we compared results obtained for ion irradiated (with two energies: 0.25 and 1.2 MeV up to 25dpa) alumina coating system. Mechanical properties of pristine and ion-irradiated specimens were studied by nanoindentation technique. Interestingly, the qualitative relationship between nanohardness and irradiation damage level is very similar, regardless of the energy used. The presented work proves that for some materials (e.g., hard coatings), the qualitative assessment of the mechanical changes using nanoindentation might be feasible even for shallow implantation depths.

Durability study of quasi-isotropic carbon/epoxy composites under various environmental conditions

Fibre-reinforced polymer (FRP) composites are gaining more attention for civil, automobile, aircraft and marine applications due to their excellent properties. The present work investigated the effect of ageing on mechanical properties of the autoclave-cured quasi-isotropic carbon/epoxy prepreg composites. The specimens were aged at artificial seawater under ambient, sub-zero (− 15 °C), and humid conditions (70% RH. and 40 °C) for 12 months. The tensile, flexural and impact properties were determined at regular intervals. The gravimetric study revealed that moisture absorption behaviour depended on the medium and duration of ageing condition. The moisture absorption for the quasi-isotropic carbon/epoxy composite specimens followed a non-fickian distribution. The moisture absorption of the carbon/epoxy composite laminate specimens showed an adverse effect on their mechanical properties. The moisture absorption results revealed that composite specimens aged under ambient condition absorbed more moisture compared with sub-zero and humid conditions. It was evident from the results that there was a 36.06% reduction in tensile properties of the composite specimens aged under ambient condition in comparison with pristine specimens. In contrast, the flexural properties were affected largely at sub-zero condition, and the impact properties were largely degraded at humid condition. The failure surface morphology revealed that matrix cracking and inner fibre debonding were the major causes of degradation in mechanical properties.Graphical abstract

One-step post-treatment with amphoteric salt for simultaneous improvement of Seebeck coefficient and electrical conductivity of PEDOT: PSS thermoelectric films

Continuous acid-base treatment can achieve high thermoelectric performance for PEDOT:PSS film, but multiple surface treatments damage samples easily, lowering yield rates as well as increasing preparation costs, preventing its commercialization. To this end, we present an amphoteric salt-based post-treatment strategy for optimizing the charge transport properties and doping levels of PEDOT:PSS films, thereby achieving high electrical conductivity (σ) and Seebeck coefficient (S) simultaneously. As a result, the optimal PEDOT:PSS thermoelectric film delivers a σ of 1462 S·cm−1 and a S of 26.2 μV·K−1, thus achieving a power factor (PF) of 100.4 μW·m−1·K−2, which is significantly higher than pristine specimens with a PF lower than 0.1 μW·m−1·K−2.

Characterization of thermal damage in graphene mortar materials using High-order sideband generation of Amplitude-modulation Vibro-acoustic technique

In this paper, an amplitude-modulated vibro-acoustic (AMVA) technique using a transmitted amplitude-modulated pump wave to achieve lower power consumption and versatility is proposed to characterize different thermal damage levels of pristine graphene mortar specimens with various dosages. In previous studies, only the primary field u1 and secondary field u2 were considered in the theoretical model. Hence, some higher-order sidebands were not included even though they are frequently presented in experimental results and useful for damage detection purposes. Therefore, a theoretical model containing higher-order effects is established to include those higher-order sidebands. A nonlinear parameter β is defined based on this theoretical model, and experimental results demonstrated that β is feasible and sensitive to characterize thermal damages as well as distinguish various dosages of cement-based materials when compared to the results of the conventional resonant frequency technique. Therefore, AMVA technique has great potential to be a reliable and efficient technique for evaluating microstructural changes in cement-based materials.

Fracture mechanics analysis of hardmetals by using artificial small-scale flaws machined at the surface through short-pulse laser ablation

Laser ablation has become an innovative treatment for cemented carbides, regarding edge rounding and surface modification, aiming to improve their tribomechanical performance. Meanwhile, the precision offered for this technique has also positioned it as an effective mean to generate micronotches used for evaluation of mechanical properties in structural materials. However, similar approach has not been attempted for hardmetals; thus, it becomes the main objective of this work. Dimple-like and elongated micronotches are introduced in one fine-grained WC-11%wtCo grade. In doing so, laser processing parameters are first optimized to attain micronotches with appropriated geometry and size, i.e. similar to critical flaws identified in broken pristine specimens. Success of the implemented approach is then validated through subsequent flexural testing, fractographic inspection and fracture mechanics analysis of the results attained on samples containing surface micronotches, as far as laser-induced residual stresses are taken into consideration. In this regard, elongated micronotches are found to exhibit lower residual stresses, and postulate themselves as the optimal option of the two micronotch types studied. The suitability of laser ablation for shaping artificial small-scale flaws opens a new route for introducing controlled defects, alike those intrinsic to processing or induced during service, key aspect for further understanding damage tolerance issues in cemented carbides.

Surface hardness of pristine and laser-treated zinc as a function of indentation load and its correlation with crystallite size valued by Williamson-Hall analysis, size-strain plot, Halder-Wagner and Wagner-Aqua models

To get a range of crystallite size, 5 N pure polycrystalline zinc specimens were shined with 50–100 Nd:YAG laser shots. Williamson-Hall, Size-Strain Plot, Halder-Wagner, and Wagner-Aqua models were employed to evaluate the crystallite size and lattice strain of pristine and laser-treated specimens. Surface hardness of the specimens were measured under 0.2 and 0.3 kgf indentation loads for 10 s. In each case, the surface hardness followed inverse Hall – Petch Relation. For a fixed number of laser shots, the surface hardness was greater for 0.2 kgf indentation load than that for 0.3 kgf. The surface hardness of pristine zinc specimen increased on treatment with 50 laser shots. With further rise in laser shots up to 80, the surface hardness progressively decreased close to that of pristine specimen. Later, it again increased for 90 laser shots and then slightly decreased for 100 laser shots.