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A Cu-Containing high-strength low-alloy (HSLA) steel was subjected to single-stage near-isothermal forging followed by different post-deformation cooling rates. The effect of different cooling media such as water, air and furnace on the microstructure evolution and mechanical characteristics of the HSLA steel was evaluated. The hierarchical microstructures of HSLA steel were investigated by different microstructural characteristic techniques to draw a correlation between microstructure and mechanical properties. The HSLA steel exhibits predominantly martensitic microstructure with or without bainite irrespective of the cooling media. However, the morphology of the martensite was found to be dependent on the cooling rate. The effect of cooling medium on grain size was systematically shown by reconstruction of prior austenite grain boundaries from electron back-scattered diffraction investigation. Faster cooling results in higher yield and tensile strength due to predominant martensitic structure while relatively slower cooling rates result in comparatively lower strength values with a corresponding increase in ductility. This is attributed to the presence of retained austenite in the HSLA steel with decreasing cooling rate. An impact toughness of ≥ 50 J was obtained at subambient temperature of − 40 °C irrespective of the cooling rate.

The interaction of pre-strain and corrosive medium can either accelerate or decelerate material failure. In the present study, the electrochemical activity of forged preforms is assessed by the open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). A powder metallurgy route was used to fabricate Al-5.6Zn-2Mg alloy with 0.8 relative density. The fabricated alloy was subjected to hot axial forging at various temperatures such as 300°C, 400°C, and 500°C under a 0.005/s strain rate. The microstructure and corrosion morphologies of sintered and forged preforms under various deformation levels and temperatures were investigated using scanning electron microscopy (SEM). After the deformation process, flow behavior, densification behavior, and electrochemical behavior are studied. Deformation behavior (true strain was linked to the local mechanical properties (hardness) and electrochemical properties (pitting potential (Epit)). The potentiodynamic polarization results showed that as the degree of deformation increased, there was a decrease in the corrosion current density and an increase in the pitting potential. Al-5.6Zn-2Mg corrosion resistance significantly improved with a degree of deformation and temperature. A mathematical model relating corrosion rate and true strain for various deformation temperatures is developed to estimate the corrosion rate for any true strain. Pitting corrosion was observed in deformed preforms as a corrosion mechanism. Because of the increased deformation degree and temperature, the corrosion morphologies showed the closing of pores.

This archival study examined the use of a university counseling center's services by international students during a 5-year period. Variables analyzed included clients' presenting concerns, students' demographic characteristics, number of [...]

Objective: To determine the general status of sports medicine training in internal medicine residency programmes in the United States. Methods: A cross sectional survey of the programme directors and chief [...]

The microstructure evolution of sintered and extruded samples of Al–4Si–0.6Mg powder alloys at various semi-solid temperature ranges of 560 °C, 580 °C, and 600 °C, holding times of 600, 1200, and 1800 s, and strain rates of 0.1, 0.2, and 0.3 s−1was studied. From the stress–strain curves and metallographic studies, Arrhenius grain growth model and Avrami dynamic recrystallization model have been formulated by means of linear regression. Parameters such as peak strain, critical strain, recrystallization fraction, and material constants have been found using the above equations. The experimental and calculated values of various material parameters agree with each other, indicating the accuracy of the developed model. Finite element method-based simulations were performed using DEFORM 2D software, and the average grain size obtained from experiments and simulations was validated by means of average grain size. The relative density of the compacted specimens as well as the extruded specimens was also simulated. The simulation results showed that large grains appeared at high temperatures and at the bottom of the specimen.

In this article, the authors present a case example of a Chinese American lesbian woman who seeks counseling for career decision making. The client's career issues stem from cultural issues [...]

In the United States of America, urban areas of the arid Southwest are prone to drought risk and changing precipitation patterns; future water supplies are uncertain. A collaborative working group of researchers and practitioners developed alternative future scenarios for 2060—sustainable water futures—that incorporate standard and novel water-adaptation strategies for the Phoenix metropolitan area (hereafter “Phoenix”) in central Arizona, USA. The authors adapted WaterSim-6, a water policy and planning model, to explore differences in water demand and supply for three scenarios as influenced by (1) runoff from the rivers that supply surface water to Phoenix, (2) population growth, (3) water use efficiency, (4) annual rainfall, and (5) land-cover land-use changes. Centralized water-management strategies (direct and indirect potable water reuse and reclaimed supplies) and decentralized strategies (rainwater harvesting and greywater use) were explored. We observed decreased reliance on surface water supplies, offset by increased municipal groundwater pumping in the Strategic scenario, but by alternative water supplies (non-potable water sources including greywater, reclaimed water, and rainwater harvested) in the Desert Wetland and Almost Zero Waste (AZW) scenarios. Even under modest policy implementation and service-connection adoption rates associated with our Strategic scenario, by 2060 alternative supplies from non-potable sources could offset 30% or more of outdoor water demand. Aggressive policy implementations associated with the AZW scenario suggest that up to 80% of outdoor water demand could likewise be met. The WaterSim platform combined with co-produced future scenarios illuminates tradeoffs in support of decision making for long-term sustainability of a water-limited region.

An investigation on strain-based formability and pore closure rate of selectively heated sintered powder metallurgical aluminum–titanium composites has been carried out to evaluate the role of heating on the curing of stresses accumulated during mechanical working. Samples with an initial relative density of 90% and an aspect ratio of 1 were prepared through the powder metallurgy technique by applying suitable powder compaction pressures with different titanium contents such as 2%, 4% and 6%. A series of upsetting tests have been carried out on the prepared porous specimens using a 0.5 MN capacity hydraulic press and the failure zone was identified through the experimental work. It was found that failure occurs in the equatorial region of the workpiece due to the accumulation of stresses and the presence of higher amounts of pores. The magnitude of these accumulated stresses and the level of pores affect the formability of the components during cold upsetting. Therefore, there is a need to relieve the accumulated stresses and reduce the pores at the failure zone of the metals. Hence, this work is aimed at relieving the accumulated stresses, reducing the porosity amounts by adopting a novel mechanism of heating in the equatorial region of the samples for various temperatures such as 100 °C, 140 °C, 195 °C, 220 °C and 250 °C. As a result, the forming limit and pore closing rate were found to improve by selectively heating the specimens at locations where stresses have accumulated. Selectively heating this location relieves the accumulated stresses and decreases the number of pores present in the preforms, thereby enabling the metal to reach still higher strain levels before the onset of failure.

The goal of the present work is to produce the efficient cutting of Ti-16Al-14Nb (α/β) alloy through wire-electric discharge machining and contemplate the terminologies such as machining ability, surface integrity and material removing capability. For this, the experimentation has been designed by considering three process parameters, pulse-on time (Ton), pulse-off time (Toff) and peak current (Ip) at three significant levels (low, high, intermediate) in L27 order designed from design of experiments. The effect of these process variables on pulse characteristics, surface roughness (Ra), kerfwidth (Kw) and material removal rate (MRR) is analyzed and mathematically modeled with analysis of variance. The results state that the highest MRR(0.521, 0.51, 0.506 mm3/sec) and low surface roughness (8.91, 8.89, 8.68 µm) values are observed at the highest level (110 µs, 15 µs, 8 A). If the pulse duration is kept at low (Ton = 40µs, Toff = 3µs), the increase in peak current from 3 A to 8 A leads to a 64.54% increase in MRR and a 52.9% increase in Ravalues. ANOVA results stated that Tonhas contributed 20.4%, 35.8% and 19.3%, and Iphas contributed 43.1%, 30.5% and 46.6% influence on MRR, Kwand Rarespectively. The voltage–current characteristics studies confirmed that the strong intense pulses at a higher peak current (8 A) resulted in the increased MRR(0.521 mm3/sec) and Ra(8.43 µm) leading to the formation of swages and ridges. The surface integrity analysis derived from Abbott–Firestone curve agreed that the lowest level has shown better skewness (Rsk = −0.274) and at highest level showed a larger deviation in skewness (Rsk= +2.672) signifies that higher asymmetry (poor) of the surface.

Isothermal hot compressive deformation tests were performed on a new high-strength low-alloy (HSLA) steel designated as “Steel A” over a range of temperatures (950–1100 °C) and constant strain rates (0.0003—1 s−1). Using the hot deformation flow behaviour data, material constants to establish constitutive relations using revised Zerilli–Armstrong and phenomenological strain-included Arrhenius model were identified. The potential of the established constitutive equations to describe the high-temperature flow behaviour of the material was then compared with standard statistical parameters such as correlation coefficient (R) and average absolute relative error (AARE). The Arrhenius constitutive model proposed by Sellars and Tegart was found to describe the high-temperature flow behaviour of “Steel A” quite accurately, and hence, this model can be used in simulations of complicated metal-forming processes. The results obtained are presented and discussed here.

The extrusion of copper-based aluminium alloys is difficult in the cold state. Extruding these alloys between the solidus and liquidus temperatures offer preferred properties on these alloys. In the present work, AA2017, a copper-based aluminium alloy has been extruded in the semi-solid state. The mechanical and metallurgical properties of the alloy vary at different temperatures between the solidus and liquidus temperatures. The aim of the present work is to optimize the process parameters, namely, temperature of billet, strain rate, approach angle and percentage reduction in area on the semi-solid extrusion of AA2017 alloy. Experiments were designed according to Taguchi experimental design and L9 orthogonal array was used to conduct the experiments. Analysis of variance (ANOVA) method was used to find the significance of every process parameter on the thixo-extrusion process responses. The results indicate that percentage reduction area is the most important factor influencing the mechanical properties of thixo-extrusion specimen followed by temperature and strain rate.

In this work, a new method of selective heating is proposed to increase the deformation behaviour of cylindrical sintered aluminium preforms during the process. Initially, cold upsetting is carried out using 0.5 MN hydraulic press machine at 0.1 s−1strain rate and the failure locations of the preforms are predicted for various initial relative densities with the aspect ratio of 1 during the deformation process. After the prediction of this failure location, various conditions of selective heating are attempted uniformly on the deformed preforms after a certain stage of deformation before the onset of the failure initiation, using portable gas cartridge at a different temperature and time to assess their consequence on formability behaviour. The detailed experimental results are evaluated for the formability of the selectively heated preforms under different variables such as flow stress, relative density, axial strain, formability stress index and stress ratio parameter. As a result, the initiation of failure and its progression can be delayed by selectively heating the samples before the onset of the failure initiation. Selective heating of the failure location may relieve the accumulated stresses and delay the onset of failure to a later strain level thereby increasing the formability of the metal.

Structural properties evaluation of semisolid extruded Al–4Cu–xMg alloy preforms have been performed in the present investigation. Pressureless sintering of Al–4 wt% Cu with varying Mg (0, 0.25, 0.5, 0.75 and 1 wt%) powder mixture was performed in an inert atmosphere. The sintering behavior and mechanical properties of all alloys were investigated at different temperatures and compositions, respectively. The maximum density and hardness (647 MPa) were found in the Al–4Cu–0.5 Mg composition sintered at 550 °C. Semisolid extrusion was carried out on sintered Al–4Cu–0.5 Mg alloys having an Initial Relative Density of 80% and 90% to find the structure–property correlation due to deformation. Extrusion was carried out in between solidus (542.7 °C) and liquidus (662.8 °C) temperatures with different solid fractions, which were derived from the TG/DTA analysis. All experiments were performed with low extrusion ratio of 1.44, strain rate of 0.1 s−1and die approach angle of 30°. Structure–property correlation study of extruded rod was performed at front end, middle part and rear end to understand the temperature and metal flow profiles during deformation process. There were no visible defects found in the demarcated samples. The presence of Al2Cu precipitate in the extruded alloy was identified by X-Ray diffractometer and scanning electron microscope with energy dispersive spectroscopy analysis. The microstructural evolution was observed in all the extruded bars by optical microscope. Micro-hardness of extruded samples was found to be 1001 MPa, which was almost two times of sintered sample.

The performance of the product components in application greatly depends on the morphological parameters and inherent capabilities of the material. In the present study, Al–ZrB2composite is made out of powder metallurgy route. Incremental weight% (0, 2, 4 and 6 wt%) of ZrB2were added into Al matrix to produce different composites. Composites were prepared by cold axial compaction followed by pressureless sintering at 550 °C for 1 h in controlled atmosphere (Ar gas). Hardness increased with the amount of ZrB2in the composite. To enhance the properties further, composites were deformed at 25, 400 and 500 °C respectively. The size, shape and orientation of the grains in the deformed composites were analyzed and correlated with the mechanical properties. The mechanical adhesion of ZrB2particle with the Al matrix was examined in different composites during different temperature conditions of deformation process. The fracture strain of the composites decreased with increase of ZrB2in the composite.

Strain hardening behaviour has significant effect on altering the properties of materials. In the present study, Al–ZrB2metal matrix composites are made through powder metallurgy route. Incremental weight percentage (wt%) of ZrB2(0, 2, 4 and 6 wt%) are added to Aluminium matrix to produce different composites. The homogenous powder mixture is compacted and pressurelessly sintered. Sintering of composites is performed over a range of 450–575 °C. The optimized sintered condition is observed at 550 °C for 1 h in controlled atmosphere (argon gas flow). The sintered compacts are strained in incremental steps in different levels up to failure. A visible crack on the bulge of the powder preform is considered as the failure. Composites are strain hardened up to failure. To evaluate the effect of temperature on strain hardening, strain hardening is carried out at different temperatures. Composites are densified with the extent of straining and hardness increases with the increase of strain. Hardness increase with the increase in temperature is maintained during strain hardening. To evaluate the corrosion behaviour of Al–ZrB2composite, potentiodynamic polarization study are performed on the strained composites. Corrosion rate decrease with the extent of straining.

The objective of this present work is to study the effect of initial relative density (IRD) on microstructure evolution of sintered Al–4wt.%B4C preforms during hot compression tests with different temperatures and strain rates. The hot compression tests of sintered Al–4wt.%B4C preforms were performed in a hydraulic press for different range of temperature (300–500) °C, strain rate (0.1–0.3 s−1), IRD (80–90)%, and deformation degree (10–50)%. The microstructure of sintered Al–4wt.%B4C preforms was characterized by optical microscope, and the average dynamic recrystallization grain size was calculated by intercept line method. It is found that the average grain size of sintered Al–4wt.%B4C deformed preforms is increased with increasing deformation temperature and IRD, whereas it decreased with increasing the strain rate and deformation degree. On the other hand, the average grain size of sintered Al–4wt.%B4C deformed preforms is dependent on the Zener–Hollomon (Z) parameter.

Climate regulation services from forests are an important leverage in global-change mitigation treaties. Like most ecosystem services, climate regulation is the product of various ecological phenomena with unique spatial features. Elucidating which abiotic and biotic factors relate to spatial patterns of climate regulation services advances our understanding of what underlies climate-mitigation potential and its variation within and across ecosystems. Here we quantify and contrast the statistical relations between climate regulation services (albedo and evapotranspiration, primary productivity, and soil carbon) and abiotic and biotic factors. We focus on 16,955 forest plots in a regional extent across the eastern United States. We find the statistical effects of forest litter and understory carbon on climate regulation services to be as strong as those of temperature-precipitation interactions. These biotic factors likely influence climate regulation through changes in vegetation and canopy density, radiance scattering, and decomposition rates. We also find a moderate relation between leaf nitrogen traits and primary productivity at this regional scale. The statistical relation between climate regulation and temperature-precipitation ranges, seasonality, and climatic thresholds highlights a strong feedback with global climate change. Our assessment suggests the expression of strong biotic influences on climate regulation services at a regional, temperate extent. Biotic homogenization and management practices manipulating forest structure and succession will likely strongly impact climate-mitigation potential. The identity, strength, and direction of primary influences differed for each process involved in climate regulation. Hence, different abiotic and biotic factors are needed to monitor and quantify the full climate-mitigation potential of temperate forest ecosystems. Forest structure and successional stage strongly influence climate regulation processes at a regional, temperate extentThe identity, strength, and direction of the main abiotic and biotic influences behind climate regulation process are not ubiquitousMultiple abiotic and biotic factors are needed to monitor and quantify the climate change-mitigation potential of temperate forests

Nickel based metal organic frameworks (Ni-MOFs) were successfully synthesized using new conjugated carboxylic acid linkers. These conjugated carboxylic acid linkers were synthesized using mild Heck coupling that led to the incorporation of functional groups not possible by traditional synthetic methods. Control of linker size allows for porosity tuning of the crystalline network and high surface area, that, in theory, results in the increased accessibility to Ni metal centers for catalysis. The resultant crystalline Ni-MOFs displayed BET areas as high as ∼314 m2g−1. To investigate their catalytic activity for conversion of oleic acid to liquid hydrocarbons, Ni-MOFs were grown on zeolite 5A beads that served as catalytic supports. The resultant catalysts displayed heptadecane selectivity as high as ∼77% at mild reaction conditions, one of the highest yields for non-noble metal containing catalysts. The catalytic activity correlated to the concentration of acid sites. A slight decrease in catalytic activity was observed after catalysts recycling.

This paper focuses on the heterogeneity of hardness distribution in the AA2014-T6 billets upset under rigid dies. The solid cylinders of height 24 mm and diameter 24 mm were compressed to different levels of strains by employing soap, boric acid and vaseline as lubricants on the faces of the billets and the friction factor (m) obtained from the ring compression test for the lubricants was given as input to the finite element software to examine strain distribution inside the cylinders. The strain distribution in the solid cylinders were correlated with the hardness distribution (VHN) and an equation was proposed to obtain the hardness of the billet. The Hill-Vonmises anisotropy factor was introduced to study the effect of anisotropy on the hardness of the deformed billet. The equation correlating the anisotropy and hardness was utilized to study the effect of anisotropy and the material parameter (C1) on the hardness of the billet.

The present investigation dealt with the study on the workability, densification and strain hardening behaviour of sintered aluminium-titanium diboride composite (Al-5%TiB2, Al-10%TiB2) preforms subjected to upsetting process. The workability data and densification mechanisms were essential for the industrial practitioners to design the process and to predict the failure strains. In the present study, Al-TiB2composite preforms with different aspect ratios and initial preform densities were compressed under triaxial stress state condition. The densification and strain hardening behaviour were analyzed by incrementally loading them till the onset of failure. The effect of the addition of TiB2content to aluminium and the effect of aspect ratio on formability were discussed in detail. The work hardening exponent, stress ratio parameters, the instantaneous density coefficient, instantaneous strain rate sensitivity and densification attained were studied.

In this investigation, the interface friction behaviour of powder metallurgical (P/M) Al–4 wt% Cu preforms was evaluated by using ring compression tests and finite element (FE) simulations at elevated temperature. P/M Al–4 wt% Cu ring specimens of different initial relative densities, 84, 87 and 90 %, were hot compressed at temperature ranging from 300 to 500 °C under graphite lubricant and dry friction conditions. FE simulation was used to derive the calibration curves, analyze the densification behaviour and geometric changes and to evaluate the metal flow. Different interface heat transfer coefficients were used to generate friction calibration curves for graphite lubricant and dry friction conditions. The results revealed that increase in temperature or decrease in initial relative density increases the interface friction factor between tool and work piece. It was found that the influence of temperature was relatively less significant in dry friction than graphite lubricant condition. In addition, the effect of temperature, initial relative density and lubricating conditions on the densification behaviour, barreling phenomenon and metal flow was evaluated. FE simulations provided detailed and accurate results of the frictional behaviour at the tool-work piece interface, and hence employment of ring compression test with FE simulations is a reliable and feasible way to evaluate interface friction behaviour of P/M components in hot compression test.