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Metal matrix composites tiles based on Ti-6Al-4V (Ti64) alloy, reinforced with 10, 20, and 40 (vol%) of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy (BEPM) and then bonded together into 3-layer laminated plates using hot isostatic pressing (HIP). The laminates were ballistically tested and demonstrated superior performance. The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates. The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate. Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP, which provides an unprecedented increase in the hardness of the layered composites. It is argued that the combination of the used two technologies, BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually. [ABSTRACT FROM AUTHOR]

It is difficult to simultaneously increase strength and toughness of austenitic stainless steels through traditional heat treatment and alloying. However, adding nano-sized ceramic particles is a potential method to manipulate the microstructure and mechanical properties of austenitic stainless steels. In this study, TiC–TiB2 nanoparticles were introduced into austenitic stainless steel using an aluminum master alloy. Adding 0.02 wt% nanoparticles effectively refined the substrates including the dendritic ferrite and austenite and reduced the grain size from 23.7 μm to 18.4 μm. The edge-to-edge model indicated that the nanoparticles act as heterogeneous cores to facilitate the nucleation rates. For mechanical properties, the addition of nanoparticles simultaneously enhanced the hardness, yield strength, tensile strength and impact toughness of the austenitic stainless steels without sacrificing the ductility. The yield strength and tensile strength of as-cast austenitic stainless steels were enhanced by 4.8% and 2.1%, 7.2% and 3.9%, 10.0% and 5.7% at the temperatures of 20 °C, 200 °C, and 400 °C, respectively. The impact toughness was improved by 4.2%, 5.9%, and 4.3% at the temperatures of −20 °C, 0 °C, and 20 °C. Also, the presence of nanoparticles increased the yield strength and tensile strength of forged austenitic stainless steels by 16.6% and 5.9%, 17.7% and 7.7%, 18.5% and 12.2% at the temperatures of 20 °C, 200 °C, and 400 °C, respectively. The impact toughness was increased by 11.6%, 8.6% and 11.3% at the temperatures of −20 °C, 0 °C, and 20 °C. The nanoparticles refined the grains, inhibited dislocation movement, scattered large cracks and distributed the external loads more uniformly to strengthen and toughen the austenitic stainless steels. In wear tests, the nanoparticle reinforced austenitic stainless steels showed higher wear resistance against adhesive wear and abrasive wear by impeding the nucleation and growth of cracks, retarding the dislocation migration and plastic deformation and bearing the external loads. The wear volumes of as-cast and forged austenitic stainless steels were reduce by 15.7% and 21.5%. This innovative approach provided a promising strategy to produce high-performance austenitic stainless steels and serve as a reference in the development of other nanoparticle reinforced ferrous materials.

Metal matrix composites tiles based on Ti–6Al–4V (Ti64) alloy, reinforced with 10, 20, and 40 (vol%) of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy (BEPM) and then bonded together into 3-layer laminated plates using hot isostatic pressing (HIP). The laminates were ballistically tested and demonstrated superior performance. The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates. The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate. Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP, which provides an unprecedented increase in the hardness of the layered composites. It is argued that the combination of the used two technologies, BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually.

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The microstructure and grain refinement of Al-4.5Er-1Zr-1.5Ti master alloy were analyzed by the refinement experiment, OM, SEM and XRD. The results show that the grain size of pure aluminum is reduced from 14,000μm to 202μm by Al-4.5Er-1Zr-1.5Ti master alloy, which is mainly due to the nucleation promoted by Ti2Al20Er, Al3Er and Al3Ti. Plastic deformation further improves the refining effect of the material by improving the primary phase size, and the Al-4.5Er-1Zr-1.5Ti −2ARB can refine the pure aluminum from 202 mμm to 150μm, and the refinement was increased by 25.7 %. The master alloy showed a better refinement effect in Al-5Cu alloy than pure aluminum, with a grain size of 92μm and a refinement improvement of 97.8 %.

Copyright of Journal of the Chinese Society of Rare Earths is the property of Editorial Department of Journal of the Chinese Society of Rare Earths and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bányászati és Kohászati Lapok - Kohászat is the property of Hungarian Mining & Metallurgical Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A technology of producing a high-quality hafnium–nickel GfNi10 master alloy is developed: it is produced in a vacuum arc furnace with a nonconsumable electrode using a preliminary annealed pressed electrolytic hafnium powder. The total content of impurities and oxygen and nitrogen gases in the master alloy is found to be substantially lower than that in a serial GFN-10 master alloy. The character of interaction of the master alloy with the nickel melt during vacuum induction melting of the new VZhM200 cast nickel superalloy shows that, in contrast to a GFN-10 master alloy, the GfNi10 master alloy produced in VIAM gives no melt splashes during the introduction of the master alloy; this increases the assimilation of hafnium. The chemical composition and mechanical properties of a serial VKNA-1VR alloy and the new VZhL125 nickel superalloy melted with the developed master alloy correspond to the requirements of specifications for these alloys. In addition, high hafnium assimilation and low contents of gas impurities are ensured. [ABSTRACT FROM AUTHOR]

Al–3Ti–1B and Al–5Ti–1B master alloys represent the most popular modifiers for the majority of aluminum alloy groups. To date, several methods, requiring various conditions and resource costs, have been applied for producing these master alloys. The paper presents the results of a comparative analysis of methods for producing Al–3Ti–1B master alloy using both a Ti sponge and salts (K2TiF6 and KBF4) as the starting components. The degree of Ti and B recovery for three methods of the master alloy production was experimentally established. The phase and element compositions of slags were studied; the amount of fluorine gas, emitted during the master alloy production, was calculated. A method, using a titanium sponge and molten KBF4 + KCl mixture, was identified to ensure a recovery of Ti and B equal to 88.10 and 72.20%, respectively. The modifying ability of the produced master alloys was studied both according to the TP-1 method and using the laboratory and industrial unit of semi-continuous casting. [ABSTRACT FROM AUTHOR]

Titanium matrix composites (TMCs) with the addition of in situ ceramic reinforcing particulates have attracted extensive interest. Herein, additive‐manufactured Ti6Al4V/Al–5Ti–0.3C–0.2B alloys are fabricated from mixed powders by laser solid forming. The contents of Al–5Ti–0.3C–0.2B with 1.5, 2.5, and 5.0 wt% are considered. The results indicate the apparent microstructure transition from columnar grain to equiaxed grain with increasing content of Al–5Ti–0.3C–0.2B. The in situ reaction between the Ti6Al4V and Al–5Ti–0.3C–0.2B produces TiB, TiC, and Ti3AlC reinforcements. The increase of Al–5Ti–0.3C–0.2B content will refine grains and reduce α′ martensite phase, which is associated with the formation of TiB at the grain boundaries. As the content of Al–5Ti–0.3C–0.2B increases, the ultimate tensile strength of Ti6Al4V–x wt% (Al–5Ti–0.3C–0.2B) alloy increases from 993.8 MPa to 1233.6 MPa. The strength increases because of an increase of the solid phases TiB and Ti3AlC, which is ascribed to the presence of precipitation and grain refinement strengthening mechanisms. Meanwhile, the elongation of the alloy increases from 1.1% to 4.9% because the Ti3AlC phase is conducive to reducing thermal transfer and interfacial stress. These findings provide insights into the selection of reinforcement materials for optimizing mechanical properties of TMCs alloys. [ABSTRACT FROM AUTHOR]

In this paper, the effect of additive type of tungsten carbide master alloy synthesized by mechanical alloying method on the properties of plain carbon steel was investigated. For this purpose, two types of synthesized master alloys as the second phase were added to the molten steel by the induction furnace. Microstructural studies were performed by optical and electron microscopes to identify the type of matrix and the distribution of the second phase particles. The mechanical and wear properties of these composites were also investigated. The results showed that the addition of the second phase to the steel while forming the Fe–WC nano-composite led to severe fine structure and thus improved mechanical properties including hardness and yield stress. Also, due to the presence of unreacted tungsten in the master alloy, a very fine Widmanstätten needle structure is formed, which leads to improved mechanical properties. The mechanical and wear properties of the composite reinforced with primary ferrotungsten powders were better than the primary tungsten-containing sample due to the finer grains as well as better bonds of the reinforcing phase and the matrix. [ABSTRACT FROM AUTHOR]

In the present work, the effect of Al–5Ti–1B master alloy or ultrasonic melt treatment on α-Al nucleation mechanism and dendrite coherency point mechanisms of the Al–Si–Mg alloy have been studied through the thermal cooling curve and microstructural analyses. Results show that these refinement methods increased the nucleation temperature and reduced recalescence undercooling for the Al7SiMg alloy. For a processing temperature of 700 ºC, the ultrasonic melt treatment increased the difference between the liquidus and coherency temperatures ( T N - T DCP ) to 10 ºC. The T N - T DCP was further improved to 14 ºC when the same melt treatment was applied at 640 ºC. Ultrasonic melt treatment increased the solid fraction at coherency by 27% and 51% at 700 ºC and 640 ºC melt temperature, respectively. Ultrasonic melt treatment displayed the highest efficiency at lower temperatures on both refinement and dendrite coherency by promoting a more refined microstructure for the Al–Si–Mg alloy. [ABSTRACT FROM AUTHOR]

This paper presents the technology of producing, in vacuum arc furnaces, master alloys based on nickel and rare refractory metals (rhenium, ruthenium, and hafnium) of ReNi-1, RuNi-2, and HfNi10 grades. The technology involves the use of metal powders as initial components, which are pre-compressed into tablets and degassed in a vacuum electric resistance furnace. Though this process, an ultra-low content of gas impurities in the master alloys is provided, which increased their manufacturability when introduced into the melt and contributed to the quality improvement of the smelted cast heat-resistant nickel alloys. Alloys ZhS32, VZhM4, and VKNA-1VR, melted using the developed master alloys, have high chemical composition stability, low levels of harmful impurities and gases, and consistently high levels of mechanical properties, which comply with the requirements of technical specifications and alloy certificates. [ABSTRACT FROM AUTHOR]

A large quantity of scrap aircraft aluminum alloys in retired aircraft was used to produce cast aluminum alloys as raw material, resulting in a decrease of the value. In this work, the mixture of scrap aircraft aluminum alloys has been grade-maintaining recycled into 7075 aluminum alloy to maximize its recovery value. After melting, composition adjusting, refining and casting, the composition of recycled AA7075 ingots meet the requirements of GB/T 3190-2008, and the final melt is of great cleanliness. Four kinds of recycled AA7075 profiles were prepared by extrusion and T6/T73 heat treatment. The mechanical properties of all recycled profiles are superior to ASTM B209-14 and B221M-13 requirements. The T6-treated bars have the highest tensile strength (591 MPa), yield strength (534 MPa), elongation (10.0%), and stress-corrosion susceptibility factor (44.8). Nevertheless, the stress corrosion cracking, exfoliation corrosion and inter-granular corrosion resistance of the T6-treated bars still meet the requirements of aviation aluminum alloys. Scrap aircraft aluminum alloys can be regarded as master alloys for containing Zn, Mg, Cu, etc., and they have low melting point, fast melting speed, and uniform microstructure. Thus, high-quality 7075 aluminum alloys can be obtained by recycling the scrap aircraft aluminum alloys. Furthermore, the recycling process can provide some guidance for the industrial application of recycling scrap aircraft aluminum alloys.

Liquid phase sintering (LPS) of powder metallurgy (PM) components is a well-recognised strategy to enhance the densification of pressed-and-sintered compacts. This work reports the investigation on the liquid phase formation when a Fe–Ni–Mn–C–B master alloy (MA) is used as a boron carrier in combination with two iron base powders pre-alloyed with Mo. Through differential scanning calorimetry tests, quantitation of the microstructure with the help of artificial intelligence, as well as measurement of sintered density and strength as a function of sintering temperature, it was possible to unravel the mechanisms that take place before and during LPS. It was confirmed that a cascade of events takes place in the solid state prior to reaching the temperature necessary for a eutectic reaction to form a liquid. Additionally, the pre-alloyed Mo content was identified as a factor that modifies the initiation of LPS but not the LPS mechanisms per se. [ABSTRACT FROM AUTHOR]

Additively manufactured Ti6Al4V parts have only seen major application in industries such as the aerospace and medical industries, mainly due to the high cost of production of the feedstock powder. In this article, the feasibility of in situ alloying a powder blend of elemental Ti and an Al–V master alloy to produce the Ti6Al4V alloy through direct metal laser sintering is presented and discussed. In a previous study, single track formation from this powder blend was studied and analyzed to determine the optimum principal process parameters suitable for this powder blend. These process parameters were employed in this study to produce single and double layers where the effects of varied hatch distance and the employment of a rescanning strategy on the surface morphology and alloy homogeneity were investigated. Lastly, in the current study, three-dimensional specimens were produced and analyzed to determine the alloy microstructure, homogeneity, part porosity and mechanical properties. The analyses revealed that a Ti6Al4V alloy with a density of up to 99.9% and corresponding tensile strength and ductility values of up to 942.9 MPa and 17% was produced. Furthermore, a minimum Al evaporation value of 7.2% was recorded. Therefore, in situ alloying can indeed be employed to produce high-quality Ti6Al4V parts from an elemental Ti and an Al–V master alloy powder blend. [ABSTRACT FROM AUTHOR]

At present, magnesium master alloys with such rare earth metals (REM) as yttrium are used in the production of alloys of magnesium and aluminum. These alloys especially the system Mg-6Zn-1Y-0,5Zr are commonly used in the aircraft and automotive industries. The article is devoted to the exploration of the synthesis process features for ternary magnesium master alloys with yttrium and zinc. The authors used X-ray fluorescence analysis (XRF), differential thermal analysis (DTA), and X-ray spectral analysis (XRD). Optical microscopy was used to conduct microstructural studies. The thermal effects that occur during metallothermic reactions of yttrium reduction from the YF3-NaCl-KCl-CaCl2 salt mixture with a melt of magnesium and zinc were investigated, and the temperatures of these effects were determined. It has been confirmed that the metallothermic reaction of yttrium reduction proceeds from the precursors of the composition: Na1.5Y2.5F9, NaYF4, Na5Y9F32, and KY7F22, and starts at a temperature of 471 °C. The results of experimental studies of the process of metallothermic reduction of yttrium from the salt mixture YF3-NaCl-KCl-CaCl2 are presented in detail. These experiments were carried out in a pit furnace at temperatures ranging from 650 to 700 °C, and it was found that, at a synthesis temperature of 700 °C, the yttrium yield is up to 99.1–99.8%. The paper establishes rational technological regimes for the synthesis (temperature 700 °C, exposure for 25 min, the ratio of chlorides to yttrium fluoride 6:1, periodic stirring of the molten metal) at which the yttrium yield reaches up to 99.8%. The structure of the master alloy samples obtained during the experiments was studied. That structure can be distinguished by a uniform distribution of ternary intermetallic compounds (Mg3YZn6) in the bulk of the double magnesium–zinc eutectic. Studies have been carried out on testing the obtained ternary master alloy as an alloying material in the production of alloys of the Mg-6Zn-1Y-0.5Zr system, while the digestibility of yttrium ranged from 91 to 95%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four adsorption sites of Ti atoms exist at the surface of Al 4 C 3 (0001) • Ti atoms only adsorb on C-terminated (0001) surface. • H 2 adsorption site is the most stable at any coverages. • Ti adsorption atom stabilizes Al 4 C 3 (0001) slab. Al 4 C 3 phase is hypothesized to undergo a solid–solid phase transition into TiC, thereby facilitating the heterogeneous nucleation of α-Al. However, capturing this transition process experimentally is challenging, which undermines the credibility of this transition theory. In this study, first-principles calculations are employed to investigate the feasibility of Ti atom adsorption on the exposed (0001) surface of the Al 4 C 3 crystal, providing theoretical support for the phase transition hypothesis. The findings indicate that Ti adatoms can effectively adsorb on the C-terminated (0001) surface, whereas adsorption on the Al-terminated surface is thermodynamically unfavorable. Upon structural optimization, Ti adatoms at bridge site B, top site T, and hollow site H 1 , irrespective of coverage, migrate towards the most stable hollow H 2 site. Electronic structure analysis reveals that the bonding between the Ti adatom at the H 2 site and the surface layer C atoms is primarily covalent, while the bonding with subsurface layer Al atoms is metallic. Additionally, Ti atom adsorption induces polarization of the bonding electron cloud between Al and C atoms. This study provides theoretical support for the Ti-induced transformation of the Al 4 C 3 to TiC phase via surface adsorption, paving the way for the development of high-performance master alloys based on phase transition theory. [ABSTRACT FROM AUTHOR]

The grain refinement behavior of Si-3P, Si-25Mn-10P, and Al-10Si-2Fe-3P master alloys on hypereutectic Al-24Si alloy was studied. Microstructure analysis indicates that the P-containing compounds in the three master alloys are SiP, MnP, and AlP, respectively. The coarse flower-like primary silicon in the Al-24Si alloy transforms into smaller, well-distributed blocks with the addition of various master alloys. When pouring at 840 °C, the average grain size of the primary silicon refined by Si-25Mn-10P master alloy with a holding time of 30 min is about 18 μm, which is significantly smaller than those refined by Si-3P and Al-10Si-2Fe-3P master alloys. The grain size shows an increasing trend when the holding time is further prolonged. Higher holding temperature has a positive effect on the grain refinement of Si-25Mn-10P master alloy. The grain refinement mechanism of the three master alloys was also discussed.

The effect of the complex ligature with nickel and REM (Ce, La) aluminides on the structure formation, the nature of the distribution of the elements, and the microhardness of the structural constituents of Al-5 wt.% Cu aluminum alloy were investigated. On the example of microalloying of the Al-5 wt.% Cu alloy with a master alloy containing Ni and REM (Ce, La) aluminides it was shown that a redistribution of Al and Cu occurs in α-solid solution and eutectic. This is reflected in the refinement of α-solid solution and eutectic at 0.15 wt.% of the master alloy addition and, accordingly, increases the microhardness of α-solid solution by 100 MPa and eutectic by 125 MPa.

The possibility to apply an electrolytically produced master alloy for grain refinement and improvement of the properties of aluminum alloys is discussed. A commercial Al–Si–Fe alloy with addition of various amounts of an Al–Zr master alloy with 10 wt % zirconium is tested at 900°C. The influence of the zirconium content in the aluminum melt and the cooling rate on its structure and properties is analyzed. Structural analysis demonstrates that addition of 0.1 wt % zirconium decreases the average grain size by 4–5 times without variations in shape and structure. The hardness measurements of the produced alloy demonstrate that, upon addition of zirconium to high-purity aluminum, the hardness increases by 1.5 times at a zirconium content of 0.4 wt % or higher with an increase in the zirconium content. At the same time, a zirconium addition to an AK6 alloy does not influence the Brinell hardness, which is likely to be due to a more pronounced action of other alloying elements. The absence of intermetallic compounds in the produced alloy modified by an Al–Zr master alloy containing intermetallic inclusions up to 50 μm in size indicates that the initial Al–Zr master alloy can be cast into ingots and cooled under any conditions, excluding the remelting stage in a mixer and other types of treatment. [ABSTRACT FROM AUTHOR]

At present, magnesium master alloys with such rare earth metals (REM) as yttrium are used in the production of alloys of magnesium and aluminum. These alloys especially the system Mg-6Zn-1Y-0,5Zr are commonly used in the aircraft and automotive industries. The article is devoted to the exploration of the synthesis process features for ternary magnesium master alloys with yttrium and zinc. The authors used X-ray fluorescence analysis (XRF), differential thermal analysis (DTA), and X-ray spectral analysis (XRD). Optical microscopy was used to conduct microstructural studies. The thermal effects that occur during metallothermic reactions of yttrium reduction from the YF3-NaCl-KCl-CaCl2 salt mixture with a melt of magnesium and zinc were investigated, and the temperatures of these effects were determined. It has been confirmed that the metallothermic reaction of yttrium reduction proceeds from the precursors of the composition: Na1.5Y2.5F9, NaYF4, Na5Y9F32, and KY7F22, and starts at a temperature of 471 °C. The results of experimental studies of the process of metallothermic reduction of yttrium from the salt mixture YF3-NaCl-KCl-CaCl2 are presented in detail. These experiments were carried out in a pit furnace at temperatures ranging from 650 to 700 °C, and it was found that, at a synthesis temperature of 700 °C, the yttrium yield is up to 99.1–99.8%. The paper establishes rational technological regimes for the synthesis (temperature 700 °C, exposure for 25 min, the ratio of chlorides to yttrium fluoride 6:1, periodic stirring of the molten metal) at which the yttrium yield reaches up to 99.8%. The structure of the master alloy samples obtained during the experiments was studied. That structure can be distinguished by a uniform distribution of ternary intermetallic compounds (Mg3YZn6) in the bulk of the double magnesium–zinc eutectic. Studies have been carried out on testing the obtained ternary master alloy as an alloying material in the production of alloys of the Mg-6Zn-1Y-0.5Zr system, while the digestibility of yttrium ranged from 91 to 95%.

The grain refinement behavior of Si-3P, Si-25Mn-10P, and Al-10Si-2Fe-3P master alloys on hypereutectic Al-24Si alloy was studied. Microstructure analysis indicates that the P-containing compounds in the three master alloys are SiP, MnP, and AlP, respectively. The coarse flower-like primary silicon in the Al-24Si alloy transforms into smaller, well-distributed blocks with the addition of various master alloys. When pouring at 840 °C, the average grain size of the primary silicon refined by Si-25Mn-10P master alloy with a holding time of 30 min is about 18 µm, which is significantly smaller than those refined by Si-3P and Al-10Si-2Fe-3P master alloys. The grain size shows an increasing trend when the holding time is further prolonged. Higher holding temperature has a positive effect on the grain refinement of Si-25Mn-10P master alloy. The grain refinement mechanism of the three master alloys was also discussed. [ABSTRACT FROM AUTHOR]

To investigate the relationship between the solidification cooling rate and the size fluctuation of different V-containing phases, Al-4 wt. % V master alloys with various V-containing constituents were prepared at different cooling rates carried out by a wedge-shaped water-cooled copper mold, a graphite mold and a refractory mold at 1050°C, respectively. The variance of lognormal density function was used to characterize the size fluctuation of V-containing phases quantitatively. The results show that the largest size difference of both Al10V phases and Al3V phases is simultaneously present in the ingot prepared by the average solidification cooling rate of 2°C·s-1, while the smallest difference of Al10V phases in size is present in the ingot prepared by the average solidification cooling rate of 271°C·s-1. The size fluctuation of the Al3V phases first increases slightly and then decreases with increasing average solidification cooling rate in the range of 30~195°C·s-1.

The effect of the complex ligature with nickel and REM (Ce, La) aluminides on the structure formation, the nature of the distribution of the elements, and the microhardness of the structural constituents of Al-5 wt.% Cu aluminum alloy were investigated. On the example of microalloying of the Al-5 wt.% Cu alloy with a master alloy containing Ni and REM (Ce, La) aluminides it was shown that a redistribution of Al and Cu occurs in a-solid solution and eutectic. This is reflected in the refinement of a-solid solution and eutectic at 0.15 wt.% of the master alloy addition and, accordingly, increases the microhardness of a-solid solution by 100 MPa and eutectic by 125 MPa. [ABSTRACT FROM AUTHOR]