Conventional Material Processing Research Articles

Overcoming strength-ductility tradeoff with high pressure thermal treatment

Conventional material processing approaches often achieve strengthening of materials at the cost of reduced ductility. Here, we show that high-pressure and high-temperature (HPHT) treatment can help overcome the strength-ductility trade-off in structural materials. We report an initially strong-yet-brittle eutectic high entropy alloy simultaneously doubling its strength to 1150 MPa and its tensile ductility to 36% after the HPHT treatment. Such strength-ductility synergy is attributed to the HPHT-induced formation of a hierarchically patterned microstructure with coherent interfaces, which promotes multiple deformation mechanisms, including dislocations, stacking faults, microbands and deformation twins, at multiple length scales. More importantly, the HPHT-induced microstructure helps relieve stress concentration at the interfaces, thereby arresting interfacial cracking commonly observed in traditional eutectic high entropy alloys. These findings suggest a new direction of research in employing HPHT techniques to help develop next generation structural materials.

Quasi-instantaneous materials processing technology via high-intensity electrical nano pulsing

Despite many efforts, the outcomes obtained with field-assisted processing of materials still rely on long-term coupling with other electroless processes. This conceals the efficacy and the intrinsic contributions of electric current. A new device utilizing electrical nano pulsing (ENP) has been designed and constructed to bring quasi-instantaneous modifications to the micro- and nano-structure in materials. Featuring ultra-high intensity (~ 1011 A/m2) and ultra-short duration (< 1 μs), the ENP technology activates non-equilibrium structural evolutions at nanometer spatial scale and nanosecond temporal scale. Several examples are provided to demonstrate its utility far outpacing any conventional materials processing technology. The ENP technology gives a practical tool for exploring the intrinsic mechanism of electric-field effects and a pathway towards the rapid industrial manufacturing of materials with unique properties.

Characterization, LCA and FEA for an efficient ecodesign of novel stainless steel woven wire mesh reinforced recycled aluminum alloy matrix composite

The production of metal matrix composites generally requires higher energy and raw materials consumption, while generating more waste than conventional material processing. The possibility of reusing recycled aluminum as an alternative in the production of metal matrix composites has led to the interest in this research as it can contribute to aluminum waste and raw reduction as well as to environmental impact mitigation. This paper provides an in-depth investigation of a brand-new metal matrix composite that is produced by gravity casting. In turn, the process is based on recycled aluminum EN AW 6082 for the matrix that is reinforced with stainless steel AISI 304 woven wire mesh that is intended for industrial and commercial use. A detailed description of the production procedure is reviewed, as are the vales of toughness, yield and tensile strengths that were determined by standardized tensile and Charpy tests. Life Cycle Assessment and Finite Element Analysis were used to determine, respectively, the environmental impact and the residual stresses generated during the production of the specimens for the above mentioned tests. Five different opening and wire diameter configurations for the AISI 304 woven wires were studied in this work. In a comparison to recycled aluminum alloy EN AW 6082 without reinforcement, the best results were provided by the 2.177 mm × 0.6 mm configuration. These results were the following: (1) Yield, tensile strength and toughness showed an increase of 245.5%, 13.62% and 175.0% respectively. (2) Life Cycle Assessment increased 8.31% for the highest environmental impact obtained (Human Toxicity). (3) The Finite Element Analysis showed that the residual stresses increased in their compressive values in −10.83 MPa, −9.925 MPa and −3.84 MPa, respectively, for the stainless steel wires, aluminum matrix and wire/matrix interfaces. From the mechanical properties, the environmental impacts and the residual stresses that were obtained, one can conclude that this study has demonstrated a technically feasible practical approach to the use of the recycled aluminum alloy EN AW 6082 using AISI 304 stainless steel woven wires as materials in the metal matrix composites production. This could lead to a substantial reduction in the volume of aluminum used and, consequently, provide environmental and economic benefits.

Effects of oxygen content on microstructure and mechanical properties of 18Ni300 maraging steel manufactured by laser directed energy deposition

Compared to conventional material processing technologies, laser directed energy deposition (LDED) belonging to additive manufacturing (AM) has many advantages and enormous commercial potential. However, the effect of external factors on the deposition process has not been completely revealed such as the oxygen content in the manufacturing environment. 18Ni300 as maraging steel has excellent mechanical performance, but oxidation inside parts could induce metallurgical defects like inclusion or cracks and impair the service life of parts. Therefore, this paper focuses on the microstructure and mechanical properties of 18Ni300 maraging steel fabricated by LDED under different oxygen contents. The control of oxygen content in the environment was achieved by changing the argon content. Experimental results indicated that the forming accuracy of specimens and process stability were effectively improved at both 500 ppm and 50 ppm oxygen contents. The width of equiaxed grain region, grain growth orientation and primary dendritic arm spacing were significantly affected by gaseous environment. In the low oxygen content group, higher microhardness values were obtained due to the effect that similar to heat treatment. The ultimate tensile strength of samples reached to 908 MPa under 50 ppm oxygen content, which exceeded the tensile strength of wrought components.

Production of Ag−ZnO powders by hot mechanochemical processing

Ag–CdO composites are still one of the most commonly used electrical contact materials in low-voltage applications owing to their excellent electrical and mechanical properties. Nevertheless, considering the restriction on using Cd due to its toxicity, it is necessary to find alternative materials that can replace these composites. In this study, the synthesis of Ag−ZnO alloys from Ag−Zn solid solutions was investigated by hot mechanochemical processing. The hot mechanochemical processing was conducted in a modified attritor mill at 138 °C under flowing O2 at 1200 cm3/min for 3.0 h. The microstructure and phase evolution were investigated using X-ray diffractometry, field emission gun scanning electron microscopy and transmission electron microscopy. The results suggest that it is possible to complete the oxidation of Ag−Zn solid solution by hot mechanochemical processing at a low temperature and short time. This novel synthesis route can produce Ag−ZnO composites with a homogeneous distribution of nanoscale ZnO precipitates, which is impossible to achieve using the conventional material processing methods. Considering the fact that the fundamental approach to improving electric contact material performance resides in obtaining uniform dispersion of the second-phase in the Ag matrix, this new processing route could open the possibility for Ag−ZnO composites to replace non-environmentally friendly Ag−CdO.

Study of metallic powder flow in discrete coaxial nozzles

Additive technologies are gradually introducing into modern manufacturing, complementing or dislodging conventional material processing technologies. This is because of they have a unique advantage in the manufacture of products. Currently, among the popular additive laser technologies the most promising and productive technology is the direct laser deposition (DLD). The distribution of powder particles in a gas-powder flow is an important parameter that determines the powder capture coefficient (PCC) and, as a consequence, the efficiency of the DLD process. The powder flow distribution depends on the shape of the particles, the stability and the parameters of supply of the carrier gas and powder. When above conditions are fulfilled, gas-powder flow becomes stationary, which allows to determine PCC. The measurements of the PCC for different amounts and cases of nozzle positions were conducted. Having analysed the experimental and calculated results we can conclude that the model of the powder stream satisfactory describes one tube nozzle.

Microwave Sintering of Advanced Composites Materials: A Review

In recent years microwave sintering has gained significant attention based on the improved mechanical properties as compared to the conventional material processing. Microwave sintering has found its applications for the processing of metal powder, metal matrix composites, ceramics and also in the processing of metal ores. This article reviews about basic processing aspects of microwaves, microwave sintering and some of its applications comparing it with the conventional processing.

Evolution of geometric and quality features during ultrasonic vibration-assisted continuous wave laser surface drilling

Recently, the processes involving simultaneous application of ultrasonic vibrations during conventional materials processing are attracting significant interests for improving process efficiency and material quality. It has been previously shown that the simultaneous application of ultrasonic vibrations (frequency of 20kHz and vibration displacement of 23μm) during continuous wave (CW) CO2 laser surface melting results in melt expulsion and formation of surface holes. In this paper, a systematic evolution of geometric features (hole depth, diameter, aspect ratio, and taper) and quality parameters (material build-up, spatter, recast layer thickness, and heat affected zone) of holes with laser irradiation time (0.05, 0.1, 0.2, 0.25, 0.35, 0.75, and 1.25s) for the ultrasonic vibration-assisted CW CO2 laser surface drilling of AISI 316 stainless steel is investigated. Also, a multi-step finite element analysis, taking into account the observations of melt expulsion from high speed photography, is presented for the prediction of laser drilled hole volume. The results indicate that the laser melting regime of the continuous wave laser-material interactions can be extended for drilling of materials, expanding the applications of these widely used lasers for flexible manufacturing.

P70] Diffusion study on Mg-based alloys: an experimental and modeling approach

Magnesium alloys are receiving global attention in transportation sectors thanks to their superior light weight capacity which allows the design of fuel efficient vehicles with lower CO2 emissions. To develop commercial Mg alloys and optimize their manufacturing processes, fundamental knowledge in thermodynamics and diffusion kinetics is indispensable. In these thermally activated processes, diffusion can play a key role in the optimization of process parameters. A good knowledge of diffusion is thus imperative to understand the relationships between the microstructure and the high temperature process parameters. In the present study, diffusion kinetics of Mg alloys was investigated by both experiments and simulations.Pure magnesium has an hcp crystal structure (c/a ratio = 1.6236) and as a result, self-diffusion of Mg shows anisotropic behavior. Anisotropic diffusion is also observed for various alloying elements such as Ag, Cd, In, Sb, and Sn in hcp Mg. Apart from Ag, the diffusion of solute elements and Mg itself along the a-axis of Mg is faster than along the c-axis. However, the anisotropic behavior of the most common alloying elements like Al and Zn has not been investigated so far. Moreover, no data are available for rare earth elements (REE) despite the fact that their importance is increasing in Mg alloys.In the present study, the anisotropic impurity diffusion coefficients of Al, Zn, Gd, and Y were found to follow the same trend as Mg-self diffusion. The diffusion coefficients along the a-axis is maximum and is about 1.3 times faster than along the c-axis in the conventional material processing temperature. In addition, the effect of the basal plane orientation of Mg on Al and Zn diffusion was investigated and it was found that the diffusion coefficients of Al and Zn in hcp Mg decrease linearly with an increase of the tilting angle of the basal plane. Interdiffusion coefficients and growth constants of all binary intermetallics in Mg-Al, -Zn, -Gd, and –Y systems were also obtained from diffusion couple experiments.The grain boundary diffusion of Al at high angle grain boundaries in polycrystalline Mg was also investigated with diffusion couple experiments. To obtain Al concentration profiles at the grain boundary, high resolution cold field emission-secondary electron microscope (CFE-SEM) energy dispersive spectroscopy (EDS) was used. Al diffusion at grain boundaries close to 75° misorientation is about two orders of magnitude higher than the one through for the bulk.In the present study, a multiphase diffusion couple simulation model was developed which can successfully explain the experimental results. A homogenization and dissolution model was also developed to explain the solution treatment process of Mg-Al and Mg-Zn alloys. The model was validated with the help of annealing experiments for the binary Mg-Al (3, 6 and 9 wt. % Al) and Mg-Zn (1.5, 4.0 and 5.5 wt. % Zn) alloys. The model was then extended to the ternary Mg-Al-Zn system to predict the homogenization and dissolution phenomenon for the AZ…

Melt expulsion during ultrasonic vibration-assisted laser surface processing of austenitic stainless steel

Simultaneous application of ultrasonic vibrations during conventional materials processing (casting, welding) and material removal processes (machining) has recently been gaining widespread attention due to improvement in metallurgical quality and efficient material removal, respectively. In this paper, ultrasonic vibration-assisted laser surface melting of austenitic stainless steel (AISI 316) is reported. While the application of ultrasonic vibrations during laser processing delays the laser interaction with material due to enhancement of surface convection, it resulted in expulsion of melt from the irradiated region (forming craters) and transition from columnar to equiaxed dendritic grain structure in the resolidified melt films. Systematic investigations on the effect of ultrasonic vibrations (with vibrations frequency of 20kHz and power output in the range of 20–40%) on the development of microstructure during laser surface melting (with laser power of 900W and irradiation time in the range of 0.30–0.45s) are reported. The results indicate that the proposed ultrasonic vibration-assisted laser processing can be designed for efficient material removal (laser machining) and improved equiaxed microstructure (laser surface modifications) during materials processing.

Ultrasonic Processing of Materials

Irradiation of high-energy ultrasonic vibration in metals and alloys generates oscillating strain and stress fields in solids, and introduces nonlinear effects such as cavitation, acoustic streaming, and radiation pressure in molten materials. These nonlinear effects can be utilized to assist conventional material processing processes. This article describes recent research at Oak Ridge National Labs and Purdue University on using high-intensity ultrasonic vibrations for degassing molten aluminum, processing particulate-reinforced metal matrix composites, refining metals and alloys during solidification process and welding, and producing bulk nanostructures in solid metals and alloys. Research results suggest that high-intensity ultrasonic vibration is capable of degassing and dispersing small particles in molten alloys, reducing grain size during alloy solidification, and inducing nanostructures in solid metals.

Corrosion-resistant coating technique for oxide-dispersion-strengthened ferritic/martensitic steel

Oxide-dispersion-strengthened (ODS) steels are attractive materials for application as fuel cladding in fast reactors and first-wall material of fusion blanket. Recent studies have focused more on high-chromium ferritic (12–18 wt% Cr) ODS steels with attractive corrosion resistance properties. However, they have poor material workability, require complicated heat treatments for recrystallization, and possess anisotropic microstructures and mechanical properties. On the other hand, low-chromium ferritic/martensitic (8–9 wt% Cr) ODS steels have no such limitations; nonetheless, they have poor corrosion resistance properties. In our work, we developed a corrosion-resistant coating technique for a low-chromium ferritic/martensitic ODS steel. The ODS steel was coated with the 304 or 430 stainless steel, which has better corrosion resistances than the low-chromium ferritic/martensitic ODS steels. The 304 or 430 stainless steel was coated by changing the canning material from mild steel to stainless steel in the conventional material processing procedure for ODS steels. Microstructural observations and micro-hardness tests proved that the stainless steels were successfully coated without causing a deterioration in the mechanical property of the low-chromium ferritic/martensitic ODS steel.

Active glass–polymer superlattice structure for photonic integration

We propose an all-laser processing approach allowing controlled growth of organic–inorganic superlattice structures of rare-earth ion doped tellurium-oxide-based glass and optically transparent polydimethyl siloxane (PDMS) polymer; the purpose of which is to illustrate the structural and thermal compatibility of chemically dissimilar materials at the nanometer scale. Superlattice films with interlayer thicknesses as low as 2 nm were grown using pulsed laser deposition (PLD) at low temperatures (100 °C). Planar waveguides were successfully patterned by femtosecond-laser micro-machining for light propagation and efficient Er3+-ion amplified spontaneous emission (ASE). The proposed approach to achieve polymer–glass integration will allow the fabrication of efficient and durable polymer optical amplifiers and lossless photonic devices. The all-laser processing approach, discussed further in this paper, permits the growth of films of a multitude of chemically complex and dissimilar materials for a range of optical, thermal, mechanical and biological functions, which otherwise are impossible to integrate via conventional materials processing techniques.

고출력 다이오드 레이저(HPDL)를 이용한 탄소강 환봉의 표면변태경화

The laser material processing has replaced a conventional material processing such as a welding, cutting, drilling and surface modification and so on. LTH(Laser Transformation Hardening) is one branch of the laser surface modification process. A lot of energy is needed for the LTH process to elevate workpiece surface to temperature of the austenite transformation(A₃), which results from utilizing a beam with a larger size and lower power intensity comparatively. The absorptivity of the laser energy with respect to material depends on the wave length of a beam. This study is related to the surface hardening for the rod-shaped carbon steel by the high power diode laser(HPDL) whose beam absorptivity is better than conventional types of lasers such as CO₂ or Nd:YAG laser. Because a beam proceeds on the rotating specimen, the pretreated hardened-phase can be tempered and softened by the overlapping between hardened tracks. Accordingly, the longitudinal hardness measurement and observation of the micro structure was carried out for an assessment of the hardening characteristics. In addition, a hardening characteristics as a hardenability of materials was compared in the point of view of the hardness distribution and hardening depth and width.

Local Microstructure Control of Pure Aluminum Utilizing Fiber-Laser Aided Spot Heating System

Spot heating system utilizing a fiber-laser has been developed in order to control recrystallization, grain growth process and texture development. The newly developed system enables the laser beam to be focused onto the surface of specimen with a minimum diameter of around 10 m. The maximum power of laser in the present system is 100W. Specimens of cold rolled pure aluminum plates of 1mm thick are used for local recrystallization treatment by the spot heating. After laser-spot heating, preferentially recrystallized grains appeared in the irradiated and heat affected region with a diameter depending on the laser power density. The present system enables spot heating on any critical points of the specimen surface. Some laser-heated specimen show locally recrystallized regions occupied by almost single grain having similar crystallographic orientation as that of cold rolled matrix. But the orientation of recrystallized grain is not always the same as that of the matrix. Selective spot heating on grains having peculiar orientation would bring about a possibility of texture control that has not been achieved by means of conventional materials processing.

환경친화형 연속주조공정의 적용에 의한 난가공성 동합금 선재 제조

In a view point of full exploit age of limited resources, environmental friendly manufacturing process for production of Cu alloy including hard-to-shape alloy such as nickel-silver alloy is introduced and suggested. In the present study, the effects of continuous casting speed on mechanical property and microstructure of leaded German silver(Cu-Ni-Zn) alloy were studied and energy requirements, atmospheric CO2 emission and yield for the production of the Cu-Ni-Zn alloy was investigated quantitatively with respect to continuous casting with small cross section and conventional material processing including casting, extrusion and heat treatment. The yield for production of Cu-Ni-Zn alloy wire can be improved above 30% by application of the continuous casting with small cross when the productivity is similar. A twice of energy requirement and CO2 were consumed and emitted in extrusion process when the yield of extrusion process is considered. I

Processing of Advanced Materials with a High Frequency, Millimeter-Wave Beam Source and other Microwave Systems

Materials Science and Component Technology Directorate, Naval Research Laboratory,4555 Overlook Avenue S.W., Washington DC 20375-5343, U. S. A.'E-mail: imam@anvil.nr.navy.milKeywords: microwave processing, millimeter-wave processing, ceramics, materials, joining,coating, coating removal, rapid sinteringAbstract. An 83 GHz gyrotron-based, millimeter-wave beam system is being used in materialprocessing: in rapid sintering of oxides, ferrites, and metal-ceramic composites to retain very finegrain structure in the product for improved mechanical and electromagnetic properties; in joining ofceramic and ceramic composite materials (with unique advantages- localization of heating, permit-ting inexpensive fixturing and instrumentation and minimizing thermal damage to components; de-positing energy specifically in a narrow joint region through a guided wave effect), and in coatingdensification and coating removal where the high frequency and short wavelength permit significantenergy deposition in relatively thin coatings. In a related effort, we are using a low frequency mi-crowave system for low cost continuous production of nanophase metals. This process should pro-duce a range of nanophase metals, metal oxides and mixtures of these, in sizeable quantities and atlow cost. The results of various experiments in these areas will be discussed, as will the potential oflow and high frequency microwave processing of advanced materials.IntroductionThe authors have been investigating the use of microwave and millimeter-wave systems inmaterial processing. Such systems can have unique advantages or capabilities vs. conventionalmaterial processing. We have investigated the use of 2.45 GHz and 35 GHz cavity systems in rapidthermal processing of ceramics [1-6]. We are currently using two particular systems: an S-Band,2.45 GHz system for continuous production of nanophase oxides and metals, and an 83 GHz, mil-limeter-wave beam system for sintering, joining, coating and coating removal [7-13]. Presently, theS-Band system uses a waveguide or a resonant cavity, while the millimeter-wave system operates ina quasi-optical mode, with the millimeter-wave beam controlled by reflective optics.Typically, microwave processing is promoted on the basis of thermal efficiency or rapidheating via in-depth energy deposition. We have been exploring the use of the millimeter-wavesystem in very rapid sintering of nanophase materials, particularly ferrites. Here, the in-depthheating permits very rapid processing (<10 minute cycles) intended to preserve very fine grainstructure in the product. For small components, cycle times of less than 1 minute are possible.Theory suggests that the nature of the magnetic behavior of these ferrite materials is expected tochange dramatically at grain sizes comparable to the magnetic domain. In the case of other materi-als, the fine grain size obtained leads to excellent mechanical properties and the possibility of su-perplastic net shape forming- a possible processing route for ceramics is rapid sintering of powdercompacts to nanophase green parts, then consolidation to full density and simultaneous shaping viausing superplastic forming.We are also investigating the use of the millimeter-wave beam system in joining of ceram-ics, applying coatings to ceramics and metals, and removal of coatings from metals and composites.Here, the millimeter-wave beam system provides unique advantages. The heating effects can beconfined to an area as small as a square centimeter, permitting very localized thermal processing.

Methods for characterization of coating microstructures

The use of deposition methods to produce both overlay coatings and free-standing sheets or pieces of metals offers the possibility of producing materials with unique properties not previously obtained by conventional materials processing. These properties are closely related to the internal microstructural features of the deposited film and can be varied over wide ranges by the selection of appropriate deposition parameters and film composition. Coatings with estremely fine grain size or amorphous structures can thus be produced as well as coatings with unusual distributions of voids and cavities or with dispersions of particles of non-equilibrium phase compositions. It is thus important in the evaluation of the coating properties to take these structural features into consideration in an effort to optimize the result of the deposition process. A variety of analysing tools exist for these structural investigations, each exhibiting advantages and limitations. The purpose of the present paper is to discuss some of the methods that have proved to be useful in the course of the development of coatings.