Dependence Of Tensile Properties Research Articles

Dependence of Tensile Properties and Fracture Behaviors on the Fractions of Continuous and Discontinuous Precipitates in Peak-Aged AZ80A Magnesium Alloy.

After T5 (forging + aging) and different T6 (forging + solution + aging) heat treatments, the AZ80A Mg alloys exhibited microstructures with different fractions of continuous precipitate (CP) regions and discontinuous precipitate (DP) regions. The effects of the fractions of DP regions and CP regions on the tensile properties and fracture behaviors were investigated using microstructural characterizations and analysis. The results showed that increasing the fraction of DP regions enhanced the yield strength and tensile strength at room temperature. However, at the same high temperature, increasing the fractions of DP regions improved the elongation but deteriorated the tensile strength significantly. The different resultant tensile properties at different temperatures were caused by the different precipitation-strengthening effects in the CP and DP regions. The strengthening contribution of the DP regions was more effective at room temperature but became inferior to the effect brought about by the CP regions at high temperatures. Micro-cracks were usually initiated and propagated in the CP regions at room temperature. At high temperatures, however, micro-voids formed more easily in the DP regions, and the fracture path preferred to locate there.

Structure-tunable poly(butylene adipate-co-terephthalate) foams with enhanced mechanical performance derived by microcellular foaming with carbon dioxide as blowing agents

Poly(butylene adipate-co-terephthalate) (PBAT) is an advanced environment-friendly polymer that exhibits excellent biodegradability and outstanding mechanical properties. Microcellular foaming can endow PBAT with many admirable properties, which is significant for broadening its applications. Nevertheless, it is still challenging to prepare high-performance PBAT foams with tailored structures due to poor foaming ability. Moreover, the unclear relationships between foaming process, cellular structure, and mechanical properties significantly limit its development and application. In this study, microcellular foaming with carbon dioxide as blowing agents was developed to prepare structure-tunable PBAT foams with enhanced mechanical performance. Firstly, microcellular foaming experiments were conducted under various foaming pressures and temperatures to investigate the dependence of cellular morphology on foaming conditions. Under the investigated foaming conditions, the cell diameter and expansion ratio of PBAT foams can be manipulated in the ranges of 10–100 µm and 1–20, respectively. Furtherly, the dependence of tensile properties and compressive properties on cellular morphology was clarified. Compared with cell diameter, expansion ratio exhibited a much more significant effect on both the tensile and compressive properties of foams. In particular, PBAT foams with a tensile property of 5 MPa and a compressive property of 0.5 MPa were prepared, which possessed a lower density of 0.15 g/cm3. The prepared structure-tunable PBAT foams showed much lower density but obviously enhanced mechanical properties than the PBAT foams reported in literature.

Microstructural Evolution and Tensile Properties of a Corrosion-Resistant Ni-Based Superalloys Used for Industrial Gas Turbines

As an important mechanical property, tensile behavior has been regarded as an indicator for the creep and thermal mechanical fatigue properties of Ni-based superalloys. The tensile property of Ni-based superalloys is closely related to the amount, size, and distribution of γ'-phase and carbides. To further clarify the tensile deformation mechanism of the CM247LC alloy, this study investigated its solidification characteristics and directionally-solidified and heat-treated microstructure. The dependence of tensile properties on the varied temperature ranging between 650 and 950 ℃ is discussed in detail. It was found that the deformation mechanism at 650 ℃ is dominated by the shearing of dislocations into the γ'-precipitates to form the superlattice stacking faults. At 800 ℃, the K-W lock leads to the anomalous yield effects. At 950 ℃, the deformation mechanism is dominated by the dislocations bypassing the γ'-precipiates. The results provide a comprehensive understanding of the CM247LC alloy and are beneficial for the development of corrosion-resistant Ni-based superalloys.

β-transformed domains enhanced tensile properties and the related deformation behavior of a near alpha titanium alloy

The dependence of tensile properties and deformation behavior on microstructures of a near alpha titanium alloy Ti–3Al–2Zr–2Mo (wt.%) were investigated systematically. The positive roles of ultrafine α aciculae strengthened β-transformed (βt) domains on simultaneous enhancement of tensile strength and ductility of equiaxed and in particular bi-lamellar microstructures were explained. Compared with regular lamellar α/β microstructure, bi-lamellar microstructure consisting α/βt structures brought about a remarkable heterogeneous deformation introduced (HDI) strengthening and a much higher work hardening rate, which lead to enhanced strength and ductility. Only <a> slip systems were found to operate in the equiaxed and fully lamellar microstructures, while multiple systems including <a> and <c + a> slips were activated in bi-lamellar microstructure. Besides, the fracture modes of tensile samples with different microstructures were discussed in detail. It is suggested that introducing βt domains is feasible to simultaneously enhance tensile strength and ductility of near α titanium alloys.

Tensile Properties and Corrosion Behavior of Extruded Low-Alloyed Mg⁻1Sn⁻1Al⁻1Zn Alloy: The Influence of Microstructural Characteristics.

A low-alloyed Mg–Sn–Al–Zn system was developed and successfully fabricated through the extrusion process. The dependence of tensile properties and corrosion behavior on microstructural characteristics of the studied alloy has been investigated. After extrusion, the alloy consists of fine dynamically recrystallized (DRXed) grains of ~2.65 μm and strongly textured coarse unDRXed grains. As a consequence, the extruded alloy showed a high-tensile yield strength (YS) of 259 MPa, ultimate tensile strength (UTS) of 297 MPa and elongation (EL) of 19.0%. The strengthening response was discussed in terms of grain size, texture and solutes. The as-extruded alloy presented severe pitting corrosion and the dependence of corrosion properties on the crystallographic orientation and the formation of corrosion products was analyzed.

Tailoring Morphology and Size of Microstructure and Tensile Properties of Sn-5.5 wt.%Sb-1 wt.%(Cu,Ag) Solder Alloys

Transient directional solidification experiments, and further optical and scanning electron microscopy analyses and tensile tests, allowed the dependence of tensile properties on the micromorphology and length scale of the dendritic/cellular matrix of ternary Sn-5.5Sb-1Ag and Sn-5.5Sb-1Cu alloys to be determined. Extensive ranges of cooling rates were obtained, which permitted specific values of cooling rate for each sample examined along the length of the casting to be attributed. Very broad microstructural length scales were revealed as well as the presence of either cells or dendrites for the Ag-containing alloy. Hereafter, microstructural spacing values such as the cellular spacing, λ c, and the primary dendritic spacing, λ 1, may be correlated with thermal solidification parameters, that is, the cooling rate and the growth rate. While, for the Cu-containing Sn-Sb alloy, the β-Sn matrix is characterized only by the presence of dendritic arrangements, the Ag-containing Sn-Sb alloy is shown to have high-velocity β-Sn cells associated with high cooling rate regions, i.e., positions closer to the bottom of the alloy casting, with the remaining positions being characterized by a complex growth of β-Sn dendrites. Minor additions of Cu and Ag increase both the yield and ultimate tensile strengths when compared with the corresponding values of the binary Sn-5.5Sb alloy, with a small reduction in ductility. This has been attributed to the homogeneous distribution of the Ag3Sn and Cu6Sn5 intermetallic particles related to smaller λ 1 characterizing the dendritic zones of the ternary Sn-Sb-(Cu,Ag) alloys. In addition, the Ag-modified Sn-Sb alloy exhibited an initial wetting angle consistent with that characterizing the binary Sn-5.5Sb alloy.

Study of tool Penetration Behavior in Dissimilar Al5083 /C10100 Friction Stir Spot Welds

Friction Stir Spot Welding, is an advanced solid state material joining technique, which is gaining wide popularity in automotive and aerospace industries, as it can be efficiently used to spot join dissimilar materials, with different mechanical and metallurgical characteristics. In this investigation, dissimilar friction stir spot welds of Aluminum 5083 and C10100 Copper joints (1.5 mm thick) were made using a non-consumable tool made up of H13 tool steel material, having a cylindrical straight flat geometry with shoulder diameter of 16 mm, pin diameter 6 mm and pin length 1.5 mm. The effect of piercing and puncturing of the tool on the top (Al) plate and the bottom Cu plate were analyzed by varying the predominant friction stir spot welding process parameters like tool rotational speed, dwell time and plunge depth. The extent of flash formation on the top Al plate, top side of the bottom Cu plate, were analyzed by studying the material flow due to the frictional heat generated in the weld zone. Microstructures at the interfaces were analyzed using SEM, and the dependence of tensile properties on the extent of the deformation (depth of keyhole and protuberance) caused by the rotating tool plunge were analyzed.

Dependence of tensile properties on microstructural features of bimodal-sized ferrite/cementite steels

A medium-carbon steel was processed through different warm rolling techniques, and the microstructural features with bimodal grain size distribution were found to be different. The combination of strength and ductility was ameliorated in the steel processed through warm rolling characterized by biaxial reduction. The enhanced strength is attributed to the densely distributed fine intragranular cementite particles and the small grain size in the coarse grain regions. The enhanced uniform elongation is due to the improved work hardening behavior at the large-strain stage. This work hardening behavior is predominantly ascribed to the finely dispersed intragranular particles. The relatively small grain size with nearly equiaxed shape in the coarse grain regions helps stabilize the uniform deformation to a large strain.

Length scale of the dendritic microstructure affecting tensile properties of Al–(Ag)–(Cu) alloys

The dependence of tensile properties on the length scale of the dendritic morphology of Al–Cu, Al–Ag and Al–Ag–Cu alloys is experimentally investigated. These alloys were directionally solidified (DS) under a wide range of cooling rates [Formula: see text], permitting extensive microstructural scales to be examined. Experimental growth laws are proposed relating the primary dendritic arm spacing, [Formula: see text] to [Formula: see text] and tensile properties to [Formula: see text]. It is shown that the most significant effect of the scale of [Formula: see text] on the tensile properties is that of the ternary alloy, which is attributed to the more homogeneous distribution of the eutectic mixture for smaller [Formula: see text] and by the combined reinforcement roles of the intermetallics present in the ternary eutectic: Al2Cu and nonequilibrium Ag3Al.

Effect of geometric array of eutectic silicon particles and microscopic voids on the tensile behaviour of a cast aluminium alloy

Abstracts The present study aims to investigate the dependence of tensile properties on the microporosity variation of A356 alloy through a modified constitutive model that considers the strain-related factors and the geometric array of micro-voids and eutectic silicon particles, in comparison with the original Ghosh constitutive model. The tensile strength and elongation of the as-cast and T6-treated alloys on the microporosity variation can be theoretically described as an inverse power relationship in terms of the geometric array of the eutectic silicon particles and micro-voids and the strain-related factors such as the strain hardening exponent and strain rate sensitivity. The theoretical prediction by the modified constitutive model is in very good agreement with experimental results, typically for T6-treated alloy, even though the predicted values using the original Ghosh model exhibit a slight difference when compared with the experimental results. However, the theoretical prediction of the tensile properties of the as-cast alloy can predict values similar to the experimental results by considering the plastic constraint factor for the geometric array of the eutectic silicon particles based upon the crack propagation path. The modified constitutive model can yield various strain profiles between the strain within and outside the void regions with respect to the variation of the plastic constraint factor, which considers the geometric array and the size distribution of both constituents even at same area fraction of the micro-voids and eutectic silicon particles. The contribution of the strain hardening exponent to tensile elongation in the modified constitutive model becomes more significant than that of the original constitutive model, because of the additional contribution to the plastic constraint factor describing the geometric array of the micro-voids and eutectic silicon particles.

Nanocrystallization enabled tensile ductility of Co-based amorphous microwires

Melt-extracted amorphous Co68.15Fe4.35Si12.25B15.25 microwires were drawn at ambient temperature into different diameters and the dependence of tensile properties and microstructural evolution on the degree of deformation was investigated. The cold-drawn wire with 51% area cross-section reduction exhibits a tensile ductility of 1.64%, with a tensile strength exceeding 4000 MPa. Deformation-induced Co-rich nanocrystals were observed in the cold-drawn wires and proved to be capable of arresting the quick extension of shear bands and leading to the enhanced global plasticity of the microwires.

Effects of strain rate and temperature on tensile properties of CPVC pipe material

In this study, crosshead speed and temperature dependence of tensile properties of CPVC pipe material is investigated. Standard ASTM tensile specimens are used. Temperatures ranging from –10 to 70°C and three crosshead speeds (5, 50 and 500 mm min-1) are considered in the testing programme. The tensile test results showed that a reduction in temperature and an increase in crosshead speed have favoured brittle fracture. The yield stress and elastic modulus decreased logarithmically with decreasing crosshead speed and linearly with increasing temperature. The strain rate–temperature superposition held for both yield stress and modulus of elasticity and master curves were developed for both properties using a temperature based shift factor. A single power law relationship is developed between the shear strength and the shear modulus for all temperatures and strain rates. The value of fracture strain remained almost constant with crosshead speed at 50°C and below. At 70°C however, an enhancement of fracture strain occurred with increasing crosshead speed between 5 and 50 mm min-1 then stabilised with further increasing crosshead speed.

Constitutive Prediction on the Variability of Tensile Properties due to Microporosity Variation

The dependence of tensile properties on microporosity variation was investigated through a constitutive prediction based on previous experimental results of A356 aluminum alloy; the microporosity on a fractured surface was measured by means of quantitative fractography. The constitutive model, which takes into account the strain rate sensitivity, accurately predicts the tensile strength and elongation of the A356 alloy. In contrast, the results of a simple constitutive prediction that ignores the strain rate sensitivity diverge considerably from the overall trend of the experimental results. The significance of strain rate sensitivity on the constitutive prediction is more remarkably increased as the strain hardening exponent decreases or as the microporosity decreases.

Hemp Fibre Reinforced Poly(Lactic Acid) Composites

The potential of hemp fibre as a reinforcing material for Poly(lactic acid) (PLA) was investigated. Good interaction between hemp fibre and PLA resulted in increases of 100% for Young’s modulus and 30% for tensile strength of composites containing 30 wt% fibre. Different predictive ‘rule of mixtures’ models (e.g. Parallel, Series and Hirsch) were assessed regarding the dependence of tensile properties on fibre loading. Limited agreement with models was observed. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) studies showed that hemp fibre increased the degree of crystallinity in PLA composites.

Constitutive prediction and dependence of tensile properties of high-pressure die-cast AM60B and AZ91D magnesium alloy on microporosity

The effect of micro-voids on the tensile property of high-pressure die-cast AM60B and AZ91D magnesium alloy was investigated through systematic experimental approaches, with a constitutive prediction on the load carrying capacity and strain-related factors. The strain rate sensitivity was measured through the incremental strain rate change test, and the microporosity was measured from a comparison between the area of the micro-void and the cross-section area through the quantitative fractography on a fractured surface. The yield strengths of the AM60B and AZ91D alloys exhibit a linear dependence upon the variation of microporosity. In addition, the UTS and elongation of both alloys have a strong dependence upon the variation of microporosity, with an inverse parabolic relationship. The constitutive prediction exhibits is in good agreement with overall trend of the tensile properties of both alloys. From the constitutive prediction, it is confirmed that the differences in the UTS and elongation of both alloys arises from the divergence of the strain hardening ability, rather than from the strain rate sensitivity.

Effect of specimen orientation and welding on the fracture and fatigue properties of 2195 Al–Li alloy

In view of the use of 2195 Al–Li alloy in the construction of super-light-weight external fuel tank of space shuttles, bulkheads of reusable single-stage-to-orbit launch vehicles and in combat ground vehicles, the dependence of tensile properties, fracture toughness and fatigue resistance of this alloy on the specimen orientation and welding is very important and was studied. The T8 base alloy, with primary strengthening precipitates of T1 (Al2CuLi) phase, contained mainly brass-type texture. After welding with AA 4043 filler alloy, the fusion zone (FZ) consisted of T (AlLiSi) phase and in the heat-affected zone (HAZ) T1 phase was replaced by TB (Al7Cu4Li) phase, and micro-cracks were observed. The post-weld heat treatment (PWHT) resulted in the spheroidization of primary T phase and the precipitation of more T particles in the FZ, and the dissolution of TB phase and the re-precipitation of T1 phase in the HAZ. The yield strength, fracture toughness and fatigue threshold of the 2195-T8 alloy was observed to depend on the specimen orientation, with the lowest values obtained at 45° to the rolling direction. Welding resulted in a reduction in the tensile properties and fatigue strength. The post-weld heat treatment enhanced the yield strength, but no increase in fatigue strength was observed. Fracture mechanisms in various cases were evaluated by SEM examination of fracture surfaces and are discussed.

Effect of tempering temperature and time on tensile properties of F82H irradiated by neutrons

The dependence of tensile properties on tempering time and temperature was examined for a martensitic steel F82H irradiated at 250 °C to a neutron dose of 1.9 dpa in the Japan Materials Testing Reactor. The specimens were first normalized at 1040 °C for 0.5 h and tempered at 750 °C for 1 h. A second heat treatment was performed at temperatures from 750 to 800 °C for 0.5 h after the normalizing at 1040 °C for 0.5 h. The second tempering time at 750 °C was varied from 0.5 to 10 h. The tensile specimens of F82H + 2Ni, pure iron and Fe + 0.1C were also irradiated. Tensile tests were carried out at room temperature. The radiation hardening of F82H was significantly relieved by the second heat treatment, and it was smaller than that of the first heat treated other steels. The radiation hardening depended on the tempering conditions and tended to increase with increasing the temperature and time of tempering.

Physicochemical changes in UV- exposed low- density polyethylene films

Unstabilized low-density polyethylene (LDPE) films and films formulated with hindered amine light stabilizer (HALS) were exposed to UV-radiation; and the physicochemical changes during photooxidation processes have been investigated using tensile, FTIR spectro-photometric and thermal analytical (DSC) techniques. The dependence of tensile properties (elongation- and stress-at-break), carbonyl index and heat of fusion on UV-irradiation time have been discussed. The use of HALS is found to be effective in maintaining the UV- mechanical properties of the LDPE films. The experimental results showed that there exists no correlation between mechanical properties and carbonyl index, whereas crystallinity correlates well with carbonyl index in unstabilized and stabilized films for irradiation times greater than 100 h. The rate of formation of carbonyl groups is found to be dependent on UV exposure time. Crystallinity of the film samples is strongly influenced by both exposure time and presence of HALS.

Brittle‐to‐ductile transition temperature and its controlling mechanism in ti‐47Al‐2Mn‐2Nb alloy†

Brittle‐to‐ductile transition (BDT) temperature (TBD) has been evaluated according to temperature dependence of tensile properties under different strain rates from 10‐5 to 10‐1 s‐1 in a two‐phase Ti‐47Al‐2Mn‐2Nb alloy with near lamellar microstructure. Tensile fractography was observed using a scanning electron microscope while deformation substructures were investigated using a transmission electron microscope. It was found that TBD, when defined as the temperature corresponding to 7.5% elongation, increases from 1023K to more than 1373K, the strain rate increases from 10‐5 to 10‐1 s‐1. Based on the strain rate dependence of TBD (and using the Zener‐Hollomon factor) an apparent activation energy of 324kJ/mol was obtained, which is approximate to the self‐ and inter‐diffusion activation energies in the y‐TiAl phase. Transgranular fracture and dimple fracture were found to dominate in fracture surfaces below and above TBd, respectively. Furthermore, the most popular 1/2<110] ordinary dislocations were found to begin to climb around TBD. All this evidence, as well as a theoretical calculation using the Nabarro Model, add up to a conclusion that the BDT of the alloy is controlled by dislocation climbing.

The Effects of Strain Rate and Minor Baron Addition on Brittle-to-Ductile Transition Temperature in Gamma TiAl Alloy

ABSTRACTBrittle-to-ductile transition (BDT) temperature (TBD) was evaluated according to temperature dependence of tensile properties under different strain rates from 10−5to 10−1s−1in two-phase Ti-47Al-2Mn-2Nb and Ti-47A1–2Mn-2Nb-0.8 TiB2alloys with nearly lamellar microstructure. Based on the strain rate dependence of the determined TBD values, apparent BDT activation energies were determined using Zener-Hollomon factor. Tensile fracture surfaces were observed using a scanning electron microscope while deformation substructures were investigated by transmission electron microscopy. It was found that the BDTT of both alloys increased sharply with the strain rate and that the minor addition of 0.8 vol% TiB2reduced TBD by about 100K at the same strain rate. The TiB2addition also decreases the apparent BDT activation energy from 324 to 256 kJ/mol. Both of these values approximate to self- or inter-diffusion of Ti and Al atoms in TiAl phase. Transgranular fracture and dimple fracture were found dominant in fracture surfaces below and above TBD, respectively. The most common 1/2&lt;110] ordinary dislocations were found to begin climb at mound TBD. All this evidence, as well as a theoretical calculation using the Nabarro Model, add up to a conclusion that the BDT is controlled by dislocation climb in both alloys.