Offset Yield Strength Research Articles

The Influence of Quenching Temperature on the Mechanical Properties of a Dual-Phase Steel with 0.094% C and 0.53% Mn

In this article, the authors have analysed the influence of quenching temperature (TQ) on the mechanical properties of a dual-phase steel with 0.094 % C and 0.53% Mn. In order to obtain a ferrite-martensite structure, specimens of this material have been the subjected to intercritical quenching that consisted of heating at 750, 770, 790, 810 and 830 °C, maintaining for 30 minutes and cooling in water. These specimens have then been subjected to metallographic analysis and tensile test in order to determine the volume fraction of martensite (VM) in the structure, ultimate tensile strength (Rm), the 0.2% offset yield strength (Rp0.2), the total elongation (A5) and the Rp0.2/Rm ratio.

Strengthening in Al alloy nano composites fabricated by ultrasound assisted solidification technique

Effect of temperatures of high power ultrasonic processing (700°C, 725°C, 750°C, and 775°C) on the distribution of 1wt% Al2O3 nano-particles in Al6061 alloy melt is studied. From the microstructural examination, it is observed that nano particles are better dispersed in the alloy matrix with increasing ultrasonic processing temperature. Some agglomerated reinforcement particles are seen at lower ultrasonic processing temperature of 700°C. As compared to the base alloy, mechanical properties like hardness, 0.2% offset yield strength, and ultimate tensile strength increased significantly with processing temperature. This is attributed mainly to the coefficient of thermal expansion mismatch between the alloy matrix and the Al2O3 particles, followed by Orowan strengthening, and to a lesser extent to the Hall–Petch strengthening mechanism.

Heat treatment during composite extruded spring steel wire reinforced EN AW-6082

To increase the specific yield strength and the ultimate tensile strength of a unidirectionally spring steel wire – reinforced composite extruded aluminium alloy (AlMgSi1) matrix composite, investigations of heat treatment states T4 and T6 have been carried out. With respect to the quench sensitivity of the matrix material used and to reduce processing time to avoid unintended interfacial reactions, a setup for direct water quenching at the extrusion press was used and compared to air quenched extrusion profiles. The mechanical investigations showed increased ultimate tensile strength and offset yield strength for water quenched unreinforced and reinforced specimen. The deformation behaviour showed a distinct plateau region where matrix and wire deform plastically which can be explained by multiple necking of the reinforcing element. The characteristic of this region is strongly influenced by the heat treatment state. In order to characterize the interfacial properties, push-out tests were performed. Optical micrographs showed that debonding between matrix and reinforcing element mainly takes place within the matrix material. Therefore the measured debonding shear strength is strongly influenced by the heat treatment state.

Improved mechanical properties by high-energy milling and Spark Plasma Sintering of a TRIP-matrix composite

A composite reinforced with 5 vol% MgO partially stabilized zirconia and a high-alloyed TRIP-steel matrix (16% Cr, 6% Ni, 6% Mn) was processed. The objective was to trigger a phase transformation under mechanical stresses within the steel and the ceramic. Therefore, the composite was processed by both mixing (110 r/min) and dispersing by intense milling (250 r/min) of the initial powders, and subsequent Spark Plasma Sintering. During Spark Plasma Sintering, the dwell time was varied (5 min, 10 min). The steel/MgO partially stabilized zirconia interfaces were improved through the intense milling and the 10 min dwell time. Furthermore, 50% of the MgO partially stabilized zirconia transformed to the monoclinic phase under quasi-static compressive loading (10−3 s−1) and the composite had a 1% offset compressive yield strength of 665 MPa. Independent from the processing route, 65% of the steel transformed to α′-martensite.

Optimization of Friction Stir Welded, Spring Steel Wire Reinforced EN AW-6082 Profile Joints

Composite extruded, unidirectionally spring steel wire reinforced profiles have great potential for lightweight applications. Joining of these profiles represents a difficult challenge due to the different material properties, which eliminate fusion welding as a possible joining method. Friction stir welding (FSW) has recently been used to join these profiles, the disadvantage of which is that the reinforcement elements may be bent and fragmented during welding leading to drastically reduced mechanical properties compared to non-joined profiles and even to the unreinforced matrix material. In order to minimize the disturbing influences of the reinforcement elements on the joining strength, the weld axis was shifted to the retreating side, reducing wire-pin contact at the advancing side. As a second remedial measure an insert made of matrix material was placed between the joining partners before joining in order to reduce the contact on both sides. In-situ tensile tests within an X-ray micro computed tomograph (µCT) showed that shifting the weld axis could not improve the joint quality significantly. However, the use of an insert improves the offset yield strength (Rp0.2) by about 50 %.

Investigation on the solution treated behavior of economical 19Cr duplex stainless steels by Mn addition

Abstract Effect of Mn on microstructure, mechanical property and pitting corrosion of 19% Cr economical duplex stainless steels with solution temperatures ranging from 1040 to1220 °C has been investigated. The austenite content increases with more Mn addition, but decreases by increasing solution temperature, which can be inferred by trend of partition coefficient KMn with solution temperature. Meanwhile, a balanced austenite-ferrite duplex structure of solution-treated specimens was obtained with Mn addition. The impact energy at 20 °C increased with decreasing solution temperature from 1220 °C to 1040 and 1120 °C, and improved by more Mn addition due to more ductile austenite phase formation. These toughness variations were consistent with fracture morphology characteristic changing. The effect of more Mn addition and solution treatment of 1120°Con decreasing of tensile strength and 0.2% offset yield strength were slight. However, the elongation to fracture (%) fell greatly with Mn addition up to 8.1 wt.% for as-rolled and solution treated specimens due to larger deformation strains of austenite than that of ferrite. The decreasing trend of pitting corrosion potential became slower with Mn addition from 3.6 to 8.1 wt.%. The pitting corrosion resistance was lowered by increasing solution temperature due to more weakened repassivation ferrite phase formation.

Influence of alloying and testing conditions on mechanical properties and deformation behavior of 〈100〉 tungsten-based single crystals

The results of the pressure testing of mechanical properties of single crystals of pure tungsten and low-alloyed alloys W–2Re and W–1Re–1Mo (wt%) with a crystallographic orientation 〈100〉 which were prepared by plasma-arc melting are summarized. The effect of alloying and the deformation rate on these properties have also been investigated and the fracture surfaces of the individual single crystals have been evaluated with the aid of the photometric method. The differences in the deformation behavior of pure tungsten and W–Re and W–1Mo–Re alloys were observed, which relate to the particularities of rhenium and molybdenum action in the tungsten solid solution. It can be seen from the observed results that tungsten alloying with low rhenium and molybdenum contents decreased all mechanical properties when applying the deformation rate of 0.2mm/min. The biggest decrease was observed for the offset yield strength value. When testing with the deformation rate of 2mm/min, the strength limit of the W–2Re alloy increased to 2013MPa, while Rpt0.2 decreased by 33% in comparison with the pure tungsten single crystal. However, the εr value remained at the same level ∼30%. In the W–1Re–1Mo single crystal, the Rpt0.2 and Rmt values decreased, while εr increased slightly.

A multi-scale Al–Mg alloy containing ultra-fine lamellar structure

This paper reports a study on multi-scale metallic materials containing ultra-fine lamellar structure, which have received very limited attention in the published literature. In the present study, a multi-scale Al–Mg alloy, which comprises ultra-fine lamellar structure with a high density of dislocations, as well as nearly dislocation-free equiaxed ultra-fine, fine and coarse grains, was produced via partial recrystallization of the heavily cold-rolled coarse-grained (CG) counterpart. The multi-scale Al–Mg alloy achieves both high strength (~320MPa in 0.2% offset yield strength in comparison with 145MPa in 0.2% offset yield strength for the annealed CG counterpart) and high ductility (~11% in uniform elongation). Our results show that the ultra-fine lamellar structure takes a volume fraction as high as 42.5% and presents a high strength (~450MPa in 0.2% offset yield strength), enabling it to make a substantial contribution to the high overall strength of the multi-scale alloy. Interestingly, the ultra-fine lamellar structure concurrently exhibits a reasonably high ductility (~6% in uniform elongation), which benefits for the multi-scale alloy to attain the high ductility.

Synthesis of aluminum oxide dispersed α-Fe with nano sized grains by simple milling

Aluminum oxide (with 4volume% of Al2O3) dispersed α-Fe (BCC) with nano-sized grain was synthesized by reactive-cryogenic milling with a mixture of the elemental Fe, Al and Fe3O4 (Magnetite) powders as a reactant. Prior to the Hot Isostatic Press (HIP) for further densification of the materials, the milled powders were hot pressed (HPed) at the elevated temperature. The microstructure of the consolidated materials was characterized by standard metallographic techniques such as TEM (Transmission Electron Microscopy), STEM–EDS (Energy Dispersive Spectroscopy), and XRD (X-ray Diffractometer). Mechanical properties of the materials were determined by compressive yield test and micro Vickers hardness test at room temperature. The grain size estimation was attempted for the materials by XRD, using the Scherrer formula and TEM pictures. The microstructure of the materials was comprised with a mixture of a homogeneous distribution of Fe and Al2O3 nano grains. The 0.2% off-set yield strength and micro Vickers hardness of the materials were as high as 824±39MPa and 3.70±0.1GPa, respectively.

Mechanical response and deformation mechanisms of ferritic oxide dispersion strengthened steel structures produced by selective laser melting

Oxide dispersion strengthened (ODS) ferritic steels typically contain a fine dispersion of nanoscopic Y(Al, Ti) oxides, leading to an improvement in mechanical and physical properties. A rapid prototyping technique, selective laser melting (SLM), was successfully applied to consolidate as-mechanically alloyed ODS-PM2000 (Fe–19Cr–5.5Al–0.5Ti–0.5Y2O3; all wt.%) powder to fabricate solid and thin-walled builds of different thickness. This work is intended to act as a first study to investigate the tensile response of such configurations at room temperature, using miniaturized test specimens along and perpendicular to the growth direction. The 0.2% offset yield strength of as-grown wall builds was inferior to conventional PM2000 alloy (recrystallized), but could be significantly increased by conducting post-build heat treatments. Young’s modulus and yield strength showed anisotropy and were enhanced when testing perpendicular to the build growth direction. Electron backscatter diffraction revealed a strong [001] fibre texture along the growth direction, which explains the anisotropic behaviour. Additionally, studies on the morphology of the individual fracture surfaces, the grain structure of the cross-section near this region and the size distribution of ODS particles in such builds were conducted. A fine dispersion of precipitates was retained in all SLM builds, and findings suggest that a certain amount of Y is probably still in atomic solution in the as-grown condition and forms new small nanoscopic dispersoids during annealing, which lead to enhanced strengthening.

The Effects of Processing Parameters on the Structure and Mechanical Properties of Structural Pm Steels Containing Mn, Cr and Mo/ Wpływ Parametrów Wytwarzania Na Strukturę I Własności Mechaniczne Spiekanych Stali Konstrukcyjnych Zawierających Mn, Cr I Mo

Abstract The effects of processing parameters on the microstructure and mechanical properties of Fe-Mn-Cr- Mo-C PM steels are described. Pre-alloyed Astaloy CrM and Astaloy CrL, low-carbon ferromanganese and graphite powders were used as the starting materials. After pressing in rigid die, the compacts were conventionally and high temperature sintered at 1120 and 1250°C, respectively. Sintering was carried out for 60 minutes in atmospheres with different H2/N2 ratios. Cooling rate from sintering temperature was 65°C min-1 (convective cooling). The specimens were subsequently tempered at 200°C for 60 minutes in air. All specimens were tested for tensile strength (UTS), elongation (A), offset yield strength (R0:2), transverse rupture strength (TRS), impact toughness and apparent surface hardness (HV 30). After mechanical tests the microstructure of Fe-Mn-Cr-Mo-C PM steels was studied by optical microscopy. These investigations have shown that, by sintering in inexpensive and safe nitrogen-rich atmospheres, it is possible to achieve mechanical properties similar to those of specimens sintered in pure hydrogen and hydrogen-rich atmospheres.

Microstructure and tensile properties of new type of hot rolled Mg–3Sn–1Zn alloy sheet at elevated temperatures

Uniaxial tensile tests of a new type of hot rolled Mg–3Sn–1Zn (TZ31) alloy have been investigated within the temperature range of 25 to 200°C. The elongation to failure ϵf increases from 21·9% at 25°C to 79·0% at 200°C, while the 0·2% offset yield strength and peak true strength σp decrease from 141 to 60 MPa and from 264 to 91 MPa respectively. The thermal stability of globular Mg2Sn precipitates is beneficial to the strength of the rolled TZ31 alloy at elevated temperatures. However, dynamic recovery and dynamic recrystallisation play an important role in the elevated temperature elongation. Results obtained here can be used as a reference to develop inexpensive new types Mg alloys with potential for applications at elevated temperatures.

Mechanical Properties at Elevated Temperatures of an S304H-Type Austenitic Stainless Steel Processed by Warm Rolling

The effect of multiple warm to hot rolling in the temperature interval of 673 – 1273 K on the microstructures and mechanical properties of an S304H-type austenitic stainless steel was studied. The structural changes during multiple rolling are characterized by the elongation of original grains towards the rolling direction and the development of new fine grains. The average spacing between high-angle boundaries in the transverse section of the rolled samples decreases from about 0.95 to 0.4 μm with decrease in the rolling temperature from 1273 to 773 K. The multiple rolling leads to significant strengthening as revealed by tensile tests at ambient and elevated temperatures. The offset yield strength evaluated at ambient temperature increased from 480 to 1120 MPa, while the rolling temperature decreased from 1273 to 673 K. The effect of the rolling temperature on the strength becomes less pronounced with an increase of the temperature of tensile tests.

Significance of experimental data in the design of structures made from 1.4057 steel

This paper presents experimentally-obtained data which can be of importance in the design procedure of engineering components made of 1.4057 (X17CrNi16-2; AISI 431) steel. In this manner, uniaxialy tests related to determine material mechanical properties and short-time creep behavior were performed. Based on the mentioned tests, ultimate tensile strength, 0.2 offset yield strength and modulus of elasticity at low and elevated temperatures were determined. Also, creep behavior of considered steel was tested for selected temperatures and selected stress levels. According to experimentally determined Charpy impact energy an assessment of fracture toughness was made.

Comparison of material properties: Steel 20MnCr5 and similar steels

Starting from the fact that the experimental data are real data, and that the assessment of their values is of great importance in a design of the structure, this article seeks to draw attention to the designers of experimental data related to steel 20MnCr5 (1.7147, AISI 5120). In this sense, this paper presents the experimental results involving material ultimate tensile strength, yield strength, creep behavior, total fracture strain, reduction in the area as well as Charpy impact energy. All of the mentioned tests were conducted at room temperature and at elevated temperatures. Considerable tensile testing referring to determination of ultimate tensile strength as well as 0.2 offset yield strength resulted in engineering stress–strain diagrams, while those tensile testing regarding creep behavior resulted in creep curves. Also, modeling of material creep behavior using rheological models and an equation proposed by the authors can be found in this paper. Using Charpy impact energy tests, an assessment of fracture toughness was made. In addition to this, the paper presents a comparison of the material properties of 20MnCr5 steel with material properties of other similar (structural/constructional) steels.

Cyclic deformation and damage behaviour of the spring steel wire reinforced aluminium alloy EN AW-6082

The demand for lightweight materials used for constructions in automotive applications, e.g. space frames, requests for composite materials such as reinforced aluminium extrusions with a high specific stiffness and strength. This contribution shows that a spring steel wire reinforcement content of 11.1 vol% leads to a significant increase in fatigue life of monofilament composite extrusions based on the aluminium alloy, EN AW-6082, in heat treatment state T4 under stress controlled fatigue loading. As groundwork, the cyclic deformation and damage behaviour of the unreinforced matrix material is investigated in detail. Beside the determination of three stages of deformation and damage, the reason for the high fatigue strength in comparison to the quasi-static offset yield strength is also clarified. The main aim of the research focusses on the description of the mechanisms and mechanics of constituent deformation and damage evolution of 11.1 vol% spring steel wire reinforced EN AW-6082, which is presented quantitatively and qualitatively by metallographic means. The three stages represent the deformation and damage of the matrix material, whereas the fourth stage is characterised by the fatigue of the reinforcing element. Based on the knowledge of the quasi-static behaviour of the single components and the fatigue behaviour of the single matrix material, a new lifetime model is deduced from the strain response in order to predict the fatigue life for unidirectionally reinforced material systems.

MSR (Mechanically induced Self-sustaining Reaction)이 억제된 반응성 밀링에 의해 제조된 분산강화 페라이트의 미세조직과 기계적 특성

Oxide Dispersion Strengthened (ODS) Fe with <TEX>$Al_2O_3$</TEX> dispersoid was successfully produced by reactive milling with a mixture of Fe, <TEX>$Fe_3O_4$</TEX> (Magnetite), <TEX>$Fe_2O_3$</TEX> (Hematite) and Al reactants at cryogenic temperature. The milled powders were consolidated by Vacuum Hot Press (HP) at 1323 K, and the consolidated materials were characterized by Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS); the yield strength and the hardness of the consolidated materials were determined by compressive test and Vickers hardness test at room temperature. The grain size of the materials was estimated by X-ray Diffraction technique using the scherrer's formula. The TEM observations showed that the microstructure was comprised with a mixture of nanocrystalline Fe matrix and <TEX>$Al_2O_3$</TEX> nano-dispersoids with a bimodal size distribution; the 0.2% off-set yield strength of the materials was as high as <TEX>$758{\pm}29$</TEX> MPa and the Vickers hardness was <TEX>$358{\pm}2$</TEX>. The effect of the cryogenic milling and addition of extra Fe powder was discussed on the suppression of MSR (Mechanically induced Self-sustaining Reaction) for the desired microstructural evolution of ODS alloys.

Effect of Heat Treatment on Mechanical Properties of General Purpose Stainless Steel Archwire

Stainless steel has been used for orthodontic application and its properties have been continuously improved. The present study compares the mechanical properties of general purpose stainless steel archwire after heat treatment with commercial heat and non-heat treated stainless steel archwires (Highland, USA). The six parameters compared included: 1) maximum strength (MPa) 2) bending modulus (GPa) 3) bending stiffness (N/mm) 4) 0.1 offset bending force (N) 5) 0.2% offset yield strength (MPa) and 6) springback. The temperatures of heat treatment were 200°C, 250°C, 300°C and 350°C at various time duration of 10, 20 and 30 minutes. Fifteen specimens were used for each of the 12 temperature/time settings to evaluate each parameter. An Instron Universal Testing Machine was used for the three-point bend testing and the diameters were measured by a micrometer. Of all 12 settings it was found that for the condition, 300°C at 10 min and 300°C at 20 min the mechanical properties were closest to the commercial (Highland, heat-treated) stainless steel archwire and appropriate for used in clinic.

Comparison of Material Properties and Creep Behavior of 20MnCr5 and S275JR Steels

t is well known that the optimization procedure has an important role in the structure design. Furthermore, experimentally obtained data of material behavior is known to serve as the most relevant data in the mentioned design procedure. Therefore, this paper sets out to examine some experimentally determined data of the material subjected to certain environmental conditions. Based on these parameters, some analyses of material behavior can be made. In addition, data are of such nature that it is possible to make an appropriate comparison between the two investigated materials. Materials under considerations were 20MnCr5 steel and S275JR steel. Both of materials have been subjected to the same environmental conditions and the following properties can be singled out: ultimate tensile strength, 0.2 offset yield strength, the modulus of elasticity, elongation, creep behavior and Charpy impact energy. Each of the mentioned details are determined by the corresponding test, e.g. data related to strengths and to creep behavior are determined by tensile tests while impact energy is determined by Charpy impact test. In this way, the obtained values are presented in the form of the engineering stress-strain diagrams, creep curves and impact energy data.

Grain refinement and mechanical properties of low-carbon steel by means of equal channel angular pressing and annealing

Abstract Equal channel angular pressing of low-carbon steel produces an ultrafine-grained microstructure with an average (sub-)grain size of 325 nm and both coarse and fine carbides, a microhardness of 330 HV and 0.2 % offset yield strength of σ0.2 = 815 MPa. The average (sub-)grain size and the mechanical properties of the steel after equal channel angular pressing were found to be stable up to 500 °C. The composition of the carbides, their sizes and their distribution in the microstructure were analyzed in order to understand their contribution to the mechanical properties and the thermal stability of the steel. Both the high strength and the thermal stability of the steel after equal channel angular pressing are associated with the grain refinement, the substructure strengthening, and precipitation hardening.