INTERNATIONAL CONFERENCE ON ADVANCES IN MATERIALS AND PROCESSING TECHNOLOGIES (AMPT2010)
1315(2011); http://dx.doi.org/10.1063/1.3552477View Description Hide Description
Mean‐Field homogenization algorithms for materials involving two or more elastic‐plastic constituent phases are investigated. The Voigt, Reuss and Self consistent schemes which are directly applicable to multi‐phase systems are implemented. The shortcomings of these schemes are accuracy for the former two and computational efficiency for the latter. A new interpolative model is proposed which is aimed to be both computationally efficient and accurate. The results of the models are studied on the material point level for a prescribed uniaxial tensile deformation. It is observed that the response computed by the proposed scheme closely matches that computed by the Self Consistent approach.
1315(2011); http://dx.doi.org/10.1063/1.3552585View Description Hide Description
The Micro‐PIM processing technology satisfies the increasing demand in terms of smaller parts and miniaturization. Research works in this area have been carried out at FEMTO‐ST Institute by performing the injection molding with 316L stainless steel fine powders and polymer binders. Several formulations with different proportion of powders and binders as well various polymers have been tested, and then a well adapted one has been selected. The process to select the well adapted formulation and the rheological characteristics of the feedstock realized according with the selected formulation are also detailed. Several test specimens have been successfully manufactured.
1315(2011); http://dx.doi.org/10.1063/1.3552419View Description Hide Description
In this paper, effects of polyurethane foam filler on the folding behaviour of the honeycomb panels as a thin walled structure are studied, experimentally. For this purpose, some specimens of the empty and foam‐filled honeycombs were prepared. All panels had 63 hexagonal cells and made of an aluminum alloy. The effects of foam filler on the energy absorption capacity, wavelength of the folds and the number of formed folds were investigated. Folding tests were performed by a drop hammer machine. Polyurethane foam was prepared with the density of to fill the honeycomb cells. The hammer was selected with the weight of 5.48 kg and the initial drop height of 70 cm. The results of the drop hammer tests show that the foam filler causes the increasing in the energy absorption and number of the formed folds and decreasing in the wavelength of the folds.
Cyclic nanoindentation studies on CrN thin films prepared by RF sputtering on Zr‐based metallic glass1315(2011); http://dx.doi.org/10.1063/1.3552444View Description Hide Description
Cyclic nanoindentation tests were carried out to study the influence of the chromium nitride thin films on the mechanical properties of Zr‐based metallic glass. Chromium nitride thin coatings have been deposited on metallic glass substrate by RF sputtering. The deposition process was done at room temperature under nitrogen reactive gas using a metallic chromium target. The CrN films have a thickness of 300 nm. Several cyclic nanoindentation measurements were conducted on CrN films and metallic glass substrate samples at various loading rate values. We have found that the coated metallic glass sample shows high mechanical properties such as hardness and reduced elastic modulus. Cyclic nanoindentation results show a hardening behaviour for these CrN coatings. Moreover, the CrN coated on Zr‐based metallic glass was found to have a high value of resistance to crack propagation, as being analysed through the SEM pictures of the residual Vickers indentation impressions.
1315(2011); http://dx.doi.org/10.1063/1.3552455View Description Hide Description
The powder metallurgy components are being widely used for sophisticated industrial applications at a very high rate production and low cost. In modern industry, more and more it is imposed to develop new composites, such as high resistant, low density, alternative materials in order to realise multifunctional pieces. For this reason, it is very striking to use reinforced aluminium matrix composites in structural applications (automotive, aeronautical, etc.) due to their outstanding stiffness‐to‐weight and strength‐to‐weight ratios. These materials show good thermal conductivity and wear resistance and also low thermal expansion, all of which makes them very high multifunctional light weight materials. Additionally, it is very attractive way to add oxide reinforcing for improving the magnetic permeability of this composites and by this way, it can be obtained a good synchronization between thermal and electrical conductivities and magnetic permeability.
Evaluating print performance of Sn‐Ag‐Cu lead‐free solder pastes used in electronics assembly process1315(2011); http://dx.doi.org/10.1063/1.3552465View Description Hide Description
Solder paste is the most widely used interconnection material in the electronic assembly process for attaching electronic components/devices directly onto the surface of printed circuit boards, using stencil printing process. This paper evaluates the performance of three different commercially available Sn‐Ag‐Cu solder pastes formulated with different particle size distributions (PSD), metal content and alloy composition. A series of stencil printing tests were carried out using a specially designed stencil of 75 μm thickness and apertures of dimension and 500 μm pitch sizes. Solder paste printing behaviors were found related to attributes such as slumping and surface tension and printing performance was correlated with metal content and PSD. The results of the study should benefit paste manufacturers and SMT assemblers to improve their products and practices.
1315(2011); http://dx.doi.org/10.1063/1.3552476View Description Hide Description
In this work, forming limit diagram for aluminum alloy 3105 is performed experimentally using out of plane test. In addition, using ductile fracture criteria and finite element simulation, forming limit diagram of aluminum alloy 3105 is performed numerically. Finally, it is shown that the results obtained from numerical prediction are in good agreement with experimental results.
Experimental and Theoretical Investigation of Forming Limit Diagram (FLD) and Forming Limit Stress Diagram (FLSD) For Aluminum Alloy 31051315(2011); http://dx.doi.org/10.1063/1.3552488View Description Hide Description
In this paper experimental and theoretical FLD and FLSD of AA3105 are investigated. For this purpose, the forming limit diagram of Aluminum alloy 3105 using out‐of‐plane test is evaluated experimentally. Also, base of emphasis of forming limit stress diagrams and using plasticity equations, the stress limits resulted from strain limits and then forming limit stress diagram obtained. Some of the theories such as Hill theory for negative region of FLD and swift theory for positive region of FLD and Hill's 1979 yield criterion used to prediction FLD and FLSD of AA3105 and the analytical results compared with experimental results. The results show FLD and FLSD obtained from theoretical methods are in good agreement with experimental results and these methods are suitable for prediction of FLD and FLSD of AA3105.
1315(2011); http://dx.doi.org/10.1063/1.3552499View Description Hide Description
Conventional metal matrix composites (MMCs) suffer from the disadvantage of low ductility. In order to overcome this, reinforcing the metal matrix with metal particles can be taken as an alternative approach. However, processing such composites can pose serious challenges as the metal particles can either go in to solution or form undesirable intermetallics during processing through conventional routes. Friction stir processing (FSP) is emerging as a versatile tool for processing and modification of variety of materials. In the present study, metal particulate reinforced aluminum matrix composite was processed by incorporating nickel particles through friction stir processing (FSP) in one step. The microstructure was characterized by scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). SEM observations revealed that particles are uniformly dispersed in the aluminum matrix with excellent interfacial bonding. FSP also lead to grain refinement of the matrix as observed by EBSD and TEM analysis. Moreover, no harmful Al‐Ni intermetallics formed in the matrix. The mechanical properties were determined by tensile tests to evaluate the effect of metal particulate reinforcement. The novel feature of the composite is that it exhibits a threefold increase in the yield stress (0.2% proof stress) while appreciable amount of ductility is retained.
1315(2011); http://dx.doi.org/10.1063/1.3552509View Description Hide Description
Two types of cruciform specimens designed for the inverse identification of anisotropic yield surfaces of sheet metals are presented. A particular emphasis is given on the specimens design and on the sensitivity of strain fields to plastic anisotropy. The relations between experimental strain fields and identified yield surfaces are outlined for 4 materials with widely different anisotropies.
1315(2011); http://dx.doi.org/10.1063/1.3552520View Description Hide Description
The aim of this paper is to verify the technological feasibility to realize hybrid metal‐foam/composite component and the mechanical performances of the final structure. The hybrid component is composed by a cylindrical core in aluminum foam, the most used between those commercially available, and an outer layer in epoxy/S2‐glass, manufactured by filament winding technology.
A set of experimental tests have been carried out, to the aim to estimate the improvement of the hybrid component characteristics, compared to the sum of the single components (metal foam cylinder and epoxy/S2‐glass tube).
1315(2011); http://dx.doi.org/10.1063/1.3552530View Description Hide Description
The design of controlled rolling process of microalloyed steel sheets is affected by several factors. In this investigation, effect of the reheating, finishing and coiling temperatures of rolling, which are considered as the most effective parameters on microstructure of hot rolled products has been studied. For this purpose, seven different reheating temperatures between 1000 to 1300° C with 50° C increments, three different finishing temperatures of 950, 900 and 850° C below the non‐recrystallization temperature and one temperature of 800° C in the inter critical range and four different coiling temperatures of 550, 600, 650 and 700° C were chosen. By soaking the specimens in furnace, the grain coarsening temperature is obtained about 1250° C. Hence, for these kinds of steels, the reheating temperature 1200 to 1250° C is recommended. Moreover, it is observed that decreasing the coiling and finishing temperatures causes more grain refinement of microstructure and the morphology is changed from polygonal ferrite to acicular one. Findings of this research provide a good connection among reheating, finishing and coiling temperatures and microstructural features of Nb‐microalloyed steel sheets.
1315(2011); http://dx.doi.org/10.1063/1.3552541View Description Hide Description
A commercial AZ31 magnesium alloy sheet has been tested under proportional biaxial tensile loading using cruciform specimens. In order to quantitatively determine the elastic‐plastic deformation behavior of the test material, the contours of plastic work and the directions of plastic strain rates were measured over a range of equivalent plastic strain, The measured work contours and the directions of plastic strain rates have been compared with those predicted using the von Mises, Hill’48 and the Yld2000‐2d yield functions. The validity of these yield functions is discussed from viewpoints of the yield surface shape and normality flow rule in the first quadrant of the stress space. The r‐value of AZ31 was found to increase with plastic strain. The effect of the changes in r‐value on the shape of the calculated yield locus has been discussed. Furthermore, biaxial unloading tests following biaxial loading were carried out for several stress ratios. The nonlinearity of the stress‐strain curves during uniaxial and biaxial unloading was measured and quantitatively evaluated.
1315(2011); http://dx.doi.org/10.1063/1.3552552View Description Hide Description
The addition of fly ash into aluminum as reinforcement can potentially reduce the production cost and density of aluminum. However, mechanical properties of aluminum matrix composite reinforced by fly ash (MMC ALFA) have some limitations due to the characteristic of fly ash. In this study, a carbothermal reduction process of fly ash and activated carbon powder with particle size <32 μm was performed prior to produce MMC ALFA.
The process was carried out in a furnace at 1300° C in vacuum condition under argon flow. Synthesis product was analyzed by XRD with radiation. From XRD analysis, it shows that the synthesis process can produce SiC powder. The synthesis product was subsequently used as reinforcement particle. Aluminum powder was mixed with 5, 10 and 15% of the synthesized powder, and then uni‐axially compacted at pressure of 300 MPa. The compacted product was sintered for 2 hours in argon atmosphere at temperature variation of 550 and 600° C. Flexural strength, hardness and density of MMC ALFA’s product were respectively evaluated using a four point bending test method based on ASTM C1161 standard, Brinell hardness scale and Archimedes method. The result of this study shows that the increase of weight of reinforcement can significantly increase the hardness and flexural strength of MMCs. The highest hardness and flexural strength of the MMC product are and 107.5 MPa, respectively.
1315(2011); http://dx.doi.org/10.1063/1.3552561View Description Hide Description
This paper discusses the mechanical properties of Titanium Carbide (TiC) particulate reinforced aluminium‐silicon alloy matrix composite. TiC particulate reinforced LM6 alloy matrix composites were fabricated by carbon dioxide sand molding process with different particulate weight fraction. Tensile strength, hardness and microstructure studies were conducted to determine the maximum load, tensile strength, modulus of elasticity and fracture surface analysis have been performed to characterize the morphological aspects of the test samples after tensile testing. Hardness values are measured for the TiC reinforced LM6 alloy composites and it has been found that it gradually increases with increased addition of the reinforcement phase. The tensile strength of the composites increased with the increase percentage of TiC particulate.
Microstructural Evolution and Mechanical Properties of Cold‐deformed Al‐5Cu Alloy Samples After Isothermal Heat Treatments1315(2011); http://dx.doi.org/10.1063/1.3552572View Description Hide Description
Abstract.In this paper, the microscopic morphology of a semi solid Al5Cu alloy by strain induced melt activated (SIMA) process were investigated, and the effects of predeformation, microstructural evolution, aging response and hardness changes were determined. The microstructural observation shows that while the grain boundaries started to appear after 620° C, globular grains surrounded wet boundaries needed for SSP were obtained at 650° C. The grain sizes exhibited ununiformity from the outer surface to the center of the sample because of ununiform predeformation. Although isothermal heat treatments reduced hardness, age hardening gave back the hardness loss.
1315(2011); http://dx.doi.org/10.1063/1.3552582View Description Hide Description
In the plastic deformation of damaged materials, the influence of distribution of voids on the mechanical properties is an important issue. Therefore, it is necessary to control the void growth. As various sizes of voids are actually distributed in a damaged material, we have to evaluate the local damage state. The influence of clustering of multi‐size voids is also serious concern. In the present paper, aluminum sheets which contain multi‐size holes have been treated as simple models of damaged materials. These models have two pairs of holes of two different sizes. The diameter of larger holes is described as da and the diameter of smaller ones is db. The angle is defined as the inclined angle of line segments on each center of larger holes against horizontal line. Similarly, the angle is the array angle for smaller ones. The angle and are chosen to cover 0° through 60°. The behavior of plastic deformation and the interference between holes in these models under the uniaxial tensile load have been evaluated by FEM analysis. When the ratio of hole diameters is 0.5 and the array angle of larger holes is 0°, the stress in the close area of hole decreases as the angle increases. It is assumed that local plastic deformation is affected by the interference between a larger hole and a smaller hole. When the array angle is 0°, the stress in the close area of smaller holes is high regardless of the array angle In the case of the interference with holes is strong. It is indicated that the relationship between the array angle of larger holes and the development of the shear band have an influence on the local plastic deformation. As these results, it is shown that the size of distributed holes, the array pattern of holes against the loading direction and the development of the share band are mutually related to the local plastic deformation.
Probing Martensitic Transition in Nitinol Wire: A Comparison of X‐ray Diffraction and Other Techniques1315(2011); http://dx.doi.org/10.1063/1.3552318View Description Hide Description
Martensitic to austenite transformation in Nitinol wire can be measured by a number of techniques such as XRD (X‐Ray Diffraction), DSC (Differential Scanning Calorimetry), BFR (Bend and Free Recovery) and Vickers indentation recovery. A comparison of results from these varied characterisation techniques is reported here to obtain a greater understanding of the thermal‐elastic‐structural changes associated with martensitic transformation. The transformation temperatures measured by DSC were found to correspond well with the structural and mechanical information obtained from XRD, BFR and Vickers indent recovery methods. Indent recovery is a relatively new and accurate method of monitoring stress induced martensitic transformations in NiTi and is one of only a few methods of stress inducing martensitic transformation in large scale samples. It is especially useful for NiTi in the as‐cast billet form, where tensile testing is impossible. BFR is uniquely popular in the NiTi wire manufacturing sector and is recognised as the most accurate method of measuring the transformation temperature. Here the material is stressed to a representative in‐service stress level during the test. No other test uses the shape memory effect for measuring the transformation temperature of NiTi. The results show that the DSC thermogram and XRD diffractogram have a peak overlap which is a common occurrence in NiTi that has been extensively processed. The XRD method further explains the observations in the DSC thermogram and in combination they confirm the transformation temperature.
1315(2011); http://dx.doi.org/10.1063/1.3552329View Description Hide Description
Due to the increasing international competition and the resulting pricing pressure it is imperative to avoid the use of expensive alloying elements during the production of aluminium castings. The piston alloy A 332 shows an optimum combination of mechanical and casting properties and an attractive cost‐performance ratio whereas nickel is the most expensive alloying element. A substitution of nickel by a combined addition of low contents of cobalt and zirconium has the potential capacitiy to increase the mechanical properties and reduce the costs of the alloy. At Clausthal University of Technology Thermo‐Calc simulations and casting experiments were carried out to investigate the effect of the nickel subtitution. Thermo‐Calc‐simulations were made to analyze the intermetallic phases in these alloys. These simulations were evaluated by observations under optical microscope and SEM of specimens poured into permanent moulds. The size and morphology of the intermetallic phases and the primary silicon was analyzed by the use of image analysis software. The mechanical properties of the alloys were determined by tensile tests at room temperature, 250° C and 350° C. The tensile specimens were tested in as‐cast and pre‐aged condition. The effect on the castability was characterized by determining the flow length and the susceptibility to form shrinkages and hot cracks. The standard alloy A 332 and the new piston alloy with cobalt and zirconium were compared. The new alloy AlSi12,6Cu1Mg1CoZr exhibits a yield strength of 115 MPa and a tensile strength of 171 MPa at 250° C in pre‐aged condition (250° C/100 h). At 350° C the new alloy displays a yield strength of 57 MPa and a tensile strength of 85 MPa in pre‐aged condition (350° C/100h). Compared to the reference alloy AlSi12,6Cu1Ni1Mg1 the yield strength at 250° C was improved about 25% and the yield strength at 350° C about 7%. The favorable castability of the reference alloy is not affected by the substitution of nickel. These results prove the development of a heat‐resistant, thermally stable alloy without nickel. The mechanical properties and the cost‐performance ratio are superior to the standard alloy. The competitiveness of the new piston alloy was improved significantly.