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Parts made through additive manufacturing (AM) often exhibit mechanical anisotropy due to the time-based deposition of material and processing parameters. In polymer material extrusion (MEX), printed parts have weak points at layer interfaces, perpendicular to the direction of deposition. Poly(lactic acid) with chopped carbon fiber was printed on a large-format pellet printer at various extrusion rates with the same tool pathing to measure the fiber alignment with deposition via two methods and relate it to the ultimate tensile strength (UTS). Within a singular printed bead, an X-ray microscopy (XRM) scan was conducted to produce a reconstruction of the internal microstructure and 3D object data on the length and orientation of fibers. From the scan, discrete images were used in an image analysis technique to determine the fiber alignment to deposition without 3D object data on each fiber's size. Both the object method and the discrete image method showed a negative relationship between the extrusion rate and fiber alignment, with −34.64% and −53.43% alignment per extrusion multiplier, respectively, as the slopes of the linear regression. Tensile testing was conducted to determine the correlation between the fiber alignment and UTS. For all extrusion rates tested, as the extrusion multiplier increased, the percent difference in the UTS decreased, to a minimum of 8.12 ± 14.40%. The use of image analysis for the determination of the fiber alignment provides a possible method for relating the microstructure to the meso-property of AM parts, and the relationship between the microstructure and the properties establishes process–structure–property relationships for large-format AM. [ABSTRACT FROM AUTHOR]

The ultimate strength is an important property of any material for the manufacturing of components. This paper utilized the laser beam welding (LBW), due to its smaller dimension, which produces lesser distortion and process velocity is higher. Inconel 625 alloy and duplex 2205 stainless steel is having higher strength and corrosive resistance properties. Due to the above-mentioned properties, it could be used in oil and gas storage containers, marine and geothermal applications. This research work presents an investigation of various input variable effects on the output variable (ultimate tensile strength) in LBW for dissimilar materials namely, Inconel 625 alloy and duplex 2205 stainless steel. The input variables for this research are the power of a laser, welding speed, and focal position. The experimental runs are developed with the help of design of experiment (DOE) and utilized statistical design expert software. The ultimate tensile strength on different runs is measured using a universal tensile testing machine. Then from a response surface methodology and ANOVA, the optimum value of ultimate tensile strength was determined to maximize the weld joint and bead geometry. Finally, the confirmation test was carried out, it reveals the maximum error of 0.912% with the predicted value. In addition, the microstructure of the weld beads was examined using optical microscopy.

Parts made through additive manufacturing (AM) often exhibit mechanical anisotropy due to the time-based deposition of material and processing parameters. In polymer material extrusion (MEX), printed parts have weak points at layer interfaces, perpendicular to the direction of deposition. Poly(lactic acid) with chopped carbon fiber was printed on a large-format pellet printer at various extrusion rates with the same tool pathing to measure the fiber alignment with deposition via two methods and relate it to the ultimate tensile strength (UTS). Within a singular printed bead, an X-ray microscopy (XRM) scan was conducted to produce a reconstruction of the internal microstructure and 3D object data on the length and orientation of fibers. From the scan, discrete images were used in an image analysis technique to determine the fiber alignment to deposition without 3D object data on each fiber’s size. Both the object method and the discrete image method showed a negative relationship between the extrusion rate and fiber alignment, with −34.64% and −53.43% alignment per extrusion multiplier, respectively, as the slopes of the linear regression. Tensile testing was conducted to determine the correlation between the fiber alignment and UTS. For all extrusion rates tested, as the extrusion multiplier increased, the percent difference in the UTS decreased, to a minimum of 8.12 ± 14.40%. The use of image analysis for the determination of the fiber alignment provides a possible method for relating the microstructure to the meso-property of AM parts, and the relationship between the microstructure and the properties establishes process–structure–property relationships for large-format AM.

Research conducted in the current paper examines the impact of the heat treatment at temperatures from 150 °C to 300 °C with time intervals between 1 and 6 hours on susceptibility to drawing process of Zn-Al15 wire rod manufactured within the industrial continuous casting and rolling line. The mechanical properties studies proved that the heat treatment caused the increase in the ultimate tensile strength values of the alloy whereas the drawing process caused a significant decrease, which suggests that this alloy after the specific heat treatment cannot be subjected to strain hardening.

The effects of processing parameters, such as the punch speed, reheating duration and reheating temperature, on microstructure and ultimate tensile strength (UTS) of thixoformed AM60B magnesium alloy have been investigated. The results indicate that low punch speed, short reheating duration or low reheating temperature often produces the defect of cold shuts or shrinkage porosities. On the contrary, gas pores can easily form. In addition, the reheating duration or temperature also has obvious effects on the primary particle size, fraction and morphology. The three parameters can significantly affect the UTS due to their effects on the formation of pores (cold shuts, shrinkage porosities and gas pores). But they can not alter the fracture path during tensile testing and the path is always along the secondarily solidified structures between the primary particles. The effect of pore amount on the UTS is lager than that of the primary particle size, fraction or morphology. In view of their effects on the microstructure compactness and the resultant UTS, the optimized parameters are reheating for 130 minutes at 610 °C and punch speed of 3 m/s.

Research conducted in the current paper examines the impact of the heat treatment at temperatures from 150 °C to 300 °C with time intervals between 1 and 6 hours on susceptibility to drawing process of Zn-Al15 wire rod manufactured within the industrial continuous casting and rolling line. The mechanical properties studies proved that the heat treatment caused the increase in the ultimate tensile strength values of the alloy whereas the drawing process caused a significant decrease, which suggests that this alloy after the specific heat treatment cannot be subjected to strain hardening. [ABSTRACT FROM AUTHOR]

A numerical homogenization technique and morphological analysis based on the finite element method are used to compute mechanical properties of porous materials. This is achieved by considering two–dimensional matrix containing random distribution of identical non–overlapping circular or elliptical voids. Several microstructure configurations are obtained by varying the voids morphology and the porosity of the matrix. The notion of the representative volume element is used for numerical simulations in order to estimate the morphology effects of the voids on the effective ultimate tensile strength of the called Lotus – Type Porous Metals . A confrontation of the obtained numerical results of the representative microstructures for different morphologies of voids and different porosities to an analytical model and experimental data is performed. Finally, a formula improving the Boccaccini model is proposed to estimate effective tensile strength of porous metals taking into account the voids morphology. [ABSTRACT FROM AUTHOR]

This research focuses on the systematic study of a Ti-6Al-2Sn-4Zr-2Mo-Si titanium alloy and the characterization of α + β (equiaxed and bimodal) and α + β (duplex) microstructures. It provides more insights on the outstanding advantages of the duplex (α + α) micro structure, especially on its exceptional work hardening and strength-ductility balance. The heat treatment conditions required to form equiaxed, bimodal and duplex microstructures and their effects on the grain size and the phase proportion are discussed. It shows how the micro structural parameters can be controlled thanks to the heat treatment temperatures, the holding times and possible aging processes. The influence of such microstructural factors on the tensile properties of each alloy is investigated, especially on strength (proof stress, ultimate tensile strength), ductility (plastic elongation) and work hardening properties. The duplex (aα+ β) micro structure is compared with the equiaxed and bimodal microstructures and its advantages are displayed, highlighting the better strength-ductility balance and superior work hardening properties of the duplex microstructure. Indeed, the deformed microstructure of the duplex (α + β) microstructure reveals more homogeneous strain partitioning than that of the bimodal (α + β) microstructure. Thus, this work proved the potential of an optimized duplex (α + β) microstructure for the enhanced tensile properties at room temperature. Finally, a machine learning model using gradient boosting regression trees is used to quantify the importance of the microstructural factors (type of microstructure, grain size and phase ratio) on the mechanical properties. [ABSTRACT FROM AUTHOR]

Ferrium® M54® exhibits an excellent UTS/K 1C balance allowing its application in aeronautical structures. This steel belongs to the Co-Ni UHS steels family with M 2 C nanometer-size carbide precipitation during tempering. These steels provide very high strength with a very good fracture toughness thanks to the M 2 C fine precipitation during tempering, but also because coarse particles are dissolved during austenitizing without grain coarsening. The goal of this article is to identify the different carbide populations in M54®. A small addition of Ti in M54® forms a Ti-rich MC carbide precipitation that is stable at high temperature. Consequently, during austenitization at 1060 °C, all other types of coarse carbides are dissolved in the matrix without grain coarsening. As a very small part of the initial carbon content is needed to form MC carbides, efficient and intensive nanometric M 2 C carbide precipitation takes place during tempering, leading to very high final strength. Due to this double precipitation of carbides in M54®, the steel achieves an outstanding UTS/K 1C balance. [ABSTRACT FROM AUTHOR]

In the present work, the relation between ageing and retrogression temperatures on Al 6061 alloy hardness and ultimate tensile strength (UTS) was studied. It was found that higher UTS and hardness were obtained at higher ageing, retrogression temperatures, and lowest retrogression time. Controlling these parameters, alloy UTS has been improved 12% over T6 temper, showing a 40% reduction in time consumption during the thermal treatment. By means of a multiple linear regression method, a correlation has been established between UTS, hardness, and time/temperature for ageing and retrogression regimes, This correlation can be used to select adequate ageing temperature and retrogression time-temperature in order to obtain both specific UTS and hardness on aluminium 6061 alloy. [ABSTRACT FROM AUTHOR]

Strain rate, temperature, and microstructure play a significant role in the mechanical response of materials. Using non-equilibrium molecular dynamics simulations, we characterize the ductile tensile failure of a model body-centered cubic metal, tantalum, over six orders of magnitude in strain rate. Molecular dynamics calculations combined with reported experimental measurements show power-law kinetic relationships that vary as a function of dominant defect mechanism and grain size. The maximum sustained tensile stress, or spall strength, increases with increasing strain rate, before ultimately saturating at ultra-high strain rates, i.e. those approaching or exceeding the Debye frequency. The upper limit of tensile strength can be well estimated by the cohesive energy, or the energy required to separate atoms from one another. At strain rates below the Debye frequency, the spall strength of nanocrystalline Ta is less than single crystalline tantalum. This occurs in part due to the decreased flow stress of the grain boundaries; stress concentrations at grain boundaries that arise due to compatibility requirements; and the growing fraction of grain-boundary atoms as grain size is decreased into the nanocrystalline regime. In the present cases, voids nucleate at defect structures present in the microstructure. The exact makeup and distribution of defects is controlled by the initial microstructure and the plastic deformation during both compression and expansion, where grain boundaries and grain orientation play critical roles. [ABSTRACT FROM AUTHOR]

Abstract: Many studies have demonstrated a relationship between secondary dendrite arm spacing (SDAS) and the mechanical behaviour of cast aluminium–silicon alloys, both for tensile and fatigue strength. SDAS is related to the solidification time and can be predicted, with a good approximation, by finite-element simulation. However, other microstructural features can affect the tensile behaviour of cast aluminium alloys such as size and morphology of the eutectic Si particles, grain size, composition and morphology of the intermetallic compounds. The present investigation was aimed at finding valuable relationships between ultimate tensile strength and the previously mentioned microstructural parameters for the sand cast A357 aluminium alloy. The microstructural characterization was carried out by optical microscopy and image analysis on more than about 2500 micrographs. Starting from the microstructural parameters and taking into account the material hardness, a relationship able to predict the ultimate tensile strength of the alloy, with an error less than 5%, was found. This relationship can be used to evaluate the local values of the UTS in complex cast components knowing only the hardness and the microstructural parameters, even in positions where the extraction of tensile specimens is not possible. [Copyright &y& Elsevier]

• Hot axial rolling was introduced in the quenching and partitioning (Q&P) process. • The tensile strength of Q&P steel is increased by 224 MPa without loss of plasticity. • The introduction of hot deformation promotes the diffusion of carbon atoms and formation of transition carbides. • The deformation direct quenching and partitioning (DQ&P) sample shows higher work-hardening rate than Q&P sample. Quenching and partitioning (Q&P) is a heat treatment process which can obtain high strength and good plasticity matching steels. In this study, hot axial rolling was introduced in the Q&P steel and the microstructure evolutions and mechanical behaviors were compared with traditional Q&P steel. The results show that the introduction of hot deformation can retain more austenite, produce higher dislocation density and promote the precipitation of transition carbides. The higher dislocation density and more closely spaced transition carbides increase the work-hardening rate, which can not only increase the ultimate tensile strength, but also ensure no loss of plasticity, that is, improve the comprehensive mechanical properties of the Q&P steel. [ABSTRACT FROM AUTHOR]

Utilization of aluminium composites is on the rise and has wide applications in aerospace, automobile and marine industries because of their inherent properties. The aluminium composites express high wear and corrosion resistance, high strength to weight ratio, toughness etc. In the present research work, aluminum 4.5 copper alloy reinforced with MoS2 is fabricated employing stir casting method and their mechanical properties and microstructures were investigated. The percentage addition of reinforcement was made in the range from 0 wt% to 6 wt% in a step of 2 wt%. The results show a significant improvement in the micro-hardness and tensile properties on the addition of MoS2 particles, up to 4 wt% and beyond 4 wt%, these properties start decreasing. The uniform distribution of particles as well as fine-grain refinement was observed with the addition of reinforcement and thereby the density of the composite improved. The highest value of tensile strength and hardness of composites was noticed at 4 wt% of MoS2 of aluminium composite and tensile fracture mechanism was analyzed with the scanning electron microscope.

Abstract: In a hot rolled Nb–Ti and a Nb–Ti–0.09%Mo micro-alloyed steel, the ratio of yield strength to tensile strength (YS/UTS) was found to be a function of the microstructure and cooling rate in those tests where no coiling simulation and no prior deformation. The coarse bainite or acicular ferrite, which was formed at high cooling rates, raised the YS/UTS ratio under these process conditions. With coiling simulation, the ratio was not sensitive to the cooling rate or the microstructure as coiling allows the recovery of dislocations, thereby decreasing the difference in dislocation density that had arisen between a low and a high cooling rate. Deformation with a 33% reduction below the nil-recrystallisation temperature (T nr) prior to the transformation, led to a high YS/UTS ratio that ranged from 0.81 to 0.86. The prior deformation, therefore, had a stronger effect on the YS/UTS ratio than microstructural changes through cooling rate variations. [Copyright &y& Elsevier]

Aluminium LM13 alloy based hybrid particulate composites have been processed by adding boron carbide (B _4 C) and titanium diboride (TiB _2 ) particles. The wt% of titanium diboride (TiB _2 ) is varied as 0, 3, 6, 9, 12, 15 and a constant 3 wt% of boron carbide is used to prepare the composites. Stir cast route is used to fabricate the composites. The microstructures of castings are examined using computer aided image analyzer. Vicker hardness, yield strength, ultimate tensile strength and energy absorbed by the composites are examined and reported. The results show that uniform dispersion of TiB _2 and B _4 C reinforcement phases in Al LM13 alloy. Micro hardness of composites enhanced upto 36.6% when compared to Al alloy reinforced with 3 wt% of B _4 C particles. Ultimate tensile strength of Al alloy is improved from 151 MPa to 192 MPa by reinforcing 15 wt% of titanium diboride particles. LM13 aluminium alloy hybrid particulate composites offers superior vicker hardness, yield strength, utlimate tensile strength and impact strength over LM13 aluminium alloy based single particle reinforced composites.

High speed sintering, a new powder-bed fusion additive manufacturing technology, utilizes infrared lights (IR) to intensely heat and melt polymer powders. The presence of defects such as porosity, which is associated with particle coalescence, is highly dependdent on the level of energy input. This study investigate the influcence of energy input on porosity and its subsequent effects on the mechanical properties and microstructures of PEBA parts. The parts were manufactured with a variety of lamp powers, resulting in a range of energy input levels spanning from low to high. Subsequebtly, they underwent testing using Archimedes' method, followed by tensile testing. The porosity, mechanical characteristics, and energy input exhibit a strong correlation; inadequate energy input was the primary cause of pore formation. Using the reduced IR light power resulted in the following outcomes: porosity, ultimate tensile strength, and elongation of 1.37%, 7.6 MPa, and 194.2%, respectively. When the energy input was further increased, the porosity was reduced to as low as 0.05% and the ultimate tensile strength and elongation were increased to their peak values of 233.8% and 9.1 MPa, respectively. [ABSTRACT FROM AUTHOR]