Shear Punch Test Research Articles

Towards high strength MgAl2O4/Si3N4 transparent nanocomposite, using spark plasma sintering

This research investigates optical and mechanical properties of spinel/Si3N4 nanocomposite with different contents of Si3N4 (1, 3, and 5 wt%), fabricated by slip casting and spark plasma sintering. Sintering was performed at 1550 °C under 85 MPa pressure for 20 min. Some samples were then heat treated at 1000 °C for 4 h. Field emission scanning electron microscope (FESEM), X-Ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and UV-Vis spectrophotometer were used to evaluate the structure and optical properties of fabricated specimens. Mechanical properties of fabricated nanocomposite were also studied in this research using hardness and shear punch tests. Results showed that green densities and final properties of nanocomposite samples are, to a large extent, dependent on the content of Si3N4. The maximum in-line transmission in the IR-range is also affected by Si3N4 content, such a way that an increase in the content of Si3N4 from 0 to 3 wt%, is associated with a 10% decrease in the transmission. Results also showed that heat treatment does not have a major negative implication for the transmission of samples. Addition of Si3N4 nanoparticles significantly improves hardness of composite samples. The highest fracture toughness is achieved in sample with 1 wt% Si3N4. Further addition of Si3N4 up to 3 wt% dramatically decreases the fracture toughness of spinel-based nanocomposites. This has to do with the fact that addition of 3 wt% Si3N4 is associated with a significant increase in the volume fraction of porosities.

Toughness study of Borided, Borided and induction modified AISI 4340 steel

In this study, pack boriding is done on AISI 4340 steel in steel containers for 3 hours at 950°C. Boriding results in the formation of FeB or Fe2B columnar microstructure at the case. Such microstructure brings about a high brittleness of the boride layer. Induction surface modification is done on Borided samples to bring down the surface hardness. We put an effort to enhance the toughness of boride layer using 30 kW power high frequency induction heat source. The toughness of borided, borided and induction surface modified specimens are evaluated by shear punch test. Cylindrical punch of 4 mm diameter is used in this test. The toughness is calculated from the load-displacement curve. Induction modified specimens exhibit 38% improvement in toughness as compared with borided specimens. This improvement in toughness may be due to blunting of acicular boride structure in to a globular structure at the interface, smooth hardness gradient and formation of single phase Fe2B microstructure as a result of induction surface modification.

Shear Punch Testing of Neutron-Irradiated HT-9 and 14YWT

Shear punch mechanical testing was performed on neutron-irradiated HT-9 and 14YWT alloys, comparing the traditional ferritic/martensitic steel with the advanced oxide dispersion strengthened nanostructured ferritic alloy. The samples were irradiated at various temperatures between 380°C and 520°C. In HT-9, on increasing the irradiation temperature, the 1% offset shear stress and maximum shear stress decreased. The advanced 14YWT alloy was less sensitive to irradiation temperature with respect to irradiation hardening. However, it still exhibited irradiation hardening at each temperature.

Structure Property Correlation of In Situ Reinforced Al–based Metal Matrix Composite via Stir Casting

Abstract Aluminum-based in situ nanocomposites are synthesized by stir casting route. The powder materials used to develop the in situ reinforcement were mechanically milled so as to reduce the powder size in the nanoregime. The as-fabricated nanocomposite aluminum base 20 vol% (Al203 + Fe-aluminide) in situ reinforcement is characterized through X-ray diffraction, field emission scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy analysis, yet its mechanical properties were characterized through microhardness, dry sliding wear, and shear punch test. The tormented surface of the wear out and sheared specimen, investigated through FE-SEM of the as-processed composite, elicits improved tribological and shear properties as compared with pure aluminum.

Microstructure and mechanical properties of Co19Cr20Fe20Mn21Ni19 and Co19Cr20Fe20Mn21Ni19Nb0.06C0.8 high-entropy/compositionally-complex alloys after annealing

A comparative study was performed on Co19Cr20Fe20Mn21Ni19 and Co19Cr20Fe20Mn21Ni19Nb0.06C0.8 high-entropy/compositionally-complex alloys after annealing to better understand mechanical properties and their relation to the microstructure. Microscopy observations demonstrated that Nb-C addition retarded the recrystallisation and led to the formation of precipitates in the Co19Cr20Fe20Mn21Ni19 during annealing. It was also found that the Nb-C addition increased the hardness, and yield and ultimate shear strengths of Co19Cr20Fe20Mn21Ni19 alloy at both room and cryogenic temperatures. This was mainly attributed to the precipitation and solid solution strengthening mechanisms. Moreover, the results evidenced a less ductile fracture in Co19Cr20Fe20Mn21Ni19Nb0.06C0.8 alloy compared to Co19Cr20Fe20Mn21Ni19 at room and cryogenic temperatures. Microscopy analysis suggested that the observed difference in their fracture mode during shear punch testing was primarily related to the larger grain size and precipitation of Co19Cr20Fe20Mn21Ni19Nb0.06C0.8 alloy.

Effect of texture and twinning on mechanical properties and corrosion behavior of an extruded biodegradable Mg–4Zn alloy

Abstract Microstructure, texture, mechanical properties and corrosion behavior of the extruded Mg–4Zn alloy, as a biodegradable material, were investigated. A refined microstructure caused by dynamic recrystallization (DRX), and a general fiber texture were achieved after extrusion. Mechanical properties along different directions of the extruded samples were investigated using shear punch test (SPT). The shear yield stress (SYS) of 113.8 MPa obtained in the transverse direction (TD) was higher than the 106 MPa achieved for the extruded direction (ED) and 45˚ samples. This was attributed to the higher amounts of twins and also lower Schmid factor (SF) in the TD. On the other hand, encouraged activation of the basal slip system in the 45˚ samples resulted in improved room temperature formability, as indicated by the normalized displacement in the SPT diagram. Electron back scattered diffraction (EBSD) analysis of the surfaces corroded in the phosphate buffered saline (PBS) solution, showed that despite having similar grain sizes and second phase particles shape and volume fractions, surfaces containing grains near (0001) orientations and extension twins 1 ¯ 2> (TD and 45˚ samples) have lower corrosion rates, as compared to the ED specimens.

Influence of Combined Severe Plastic Deformation and Sheet Extrusion Process on the Superplastic Formability of AA 5083 Aluminum Alloy Assessed by Free Bulge Test

A combination of two forming operations is considered for producing metal sheets with improved mechanical properties. As the first operation, a newly introduced severe plastic deformation method called dual equal channel lateral extrusion (DECLE) was performed at 300 °C for different passes on the AA 5083 aluminum blocks. Following the DECLE operation, sheet extrusion was conducted to convert the bulk samples, severely deformed through various passes, into 1.8-mm-thick sheets. Mechanical properties of the processed specimens, after each step of deformation, were examined using tensile and shear punch tests. It was found that the material after three passes of DECLE and also the corresponding forwardly extruded sheet presented the greatest strength. In order to evaluate the biaxial formability of the sheets, gas bulge forming tests were conducted using a PLC-controlled gas circuit. It was shown that the material processed via three passes of DECLE operation and extrusion demonstrated the maximum biaxial superplastic formability with an effective strain associated with 400% uniaxial elongation. This sheet specimen also required the minimum forming time, coinciding with a strain rate of 4 × 10−4 s−1, which is higher than strain rate for the sheet extruded from the annealed sample.

Effects of Gd, Y, and La Rare-Earth Elements on the Microstructural Stability and Elevated-Temperature Mechanical Properties of AZ81 Magnesium Alloy

The effects of separate additions of 1 wt pct Gd, Y, and La rare-earth (RE) elements on the microstructural stability and strength of a cast AZ81 alloy were investigated in the as-cast and annealed conditions. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and optical microscopy (OM) analyses along with shear punch testing (SPT) were employed to characterize the microstructural stability and mechanical properties of the studied alloys. The main microstructural constituent in the AZ81 base alloy, Mg17Al12 intermetallic phase, showed a relatively low thermal stability, resulting in a significant strength decline at high temperatures. The incorporation of the RE elements into the base alloy not only refined the microstructure but also improved the thermal stability and high-temperature mechanical properties of the RE-containing alloys. The observed enhancement in both stability and shear strength was attributed to the reduction in the volume fraction of β-Mg17Al12 and formation of the thermally stable Al2Gd, Al2Y, and Al11La3 intermetallic particles, which suppress the grain growth throughout the annealing process. Among the employed RE elements, La was found to be the most effective one in the retention of the initial fine microstructure as well as ultimate shear strength after long-term annealing at 400 °C. This is believed to be caused by the higher number density and more uniform dispersion of the Al11La3 particles in the Mg matrix in comparison with the Al2Gd and Al2Y particles, which showed a more sparse distribution of some agglomerated particles.

Inducing superplasticity in extruded pure Mg by Zr addition

Addition of 0.7 wt% Zr to pure Mg resulted in a bimodal structure, consisting of both coarse and fine recrystallized grains with a mean grain size of 2.8 μm, and a large fraction of high angle grain boundaries after extrusion. A maximum strain rate sensitivity index of 0.42, obtained by shear punch test (SPT) at 673 K, together with activation energy of 96 kJ mol–1 indicated that grain boundary sliding controlled by grain boundary diffusion is the dominant mechanism in superplastic regime.

Superplasticity of fine-grained Mg–xGd alloys processed by multi-directional forging

Microstructural development and superplastic behavior of Mg–xGd (x = 1, 2, 3 wt%) alloys were investigated after the multi-directional forging (MDF) process. Microstructural observations of the extruded materials revealed non-homogeneous structures with bimodal grain sizes, consisting of coarse elongated grains resulting from deformation, surrounded by fine grains formed by partial dynamic recrystallization. The grain sizes of the recrystallized regions in the Mg–1Gd, Mg–2Gd and Mg–3Gd alloys were 5.6, 3.9 and 3.1 μm, respectively. After six passes of the MDF process, the bimodal grain structure disappeared as a result of complete dynamic recrystallization and almost homogeneous microstructures with the grain sizes of 2.5, 2.2 and 1.9 μm were obtained in the Mg–1Gd, Mg–2Gd and Mg–3Gd alloys, respectively. The smaller fraction of the recrystallized region in the extruded Mg–3Gd alloy and the smaller grain size in the MDF processed condition imply that more pronounced recrystallization retardation occurs through solute drag mechanism at the highest Gd content. Superplasticity was assessed by measuring the strain rate sensitivity index (m-value), through shear punch testing (SPT) in a temperature range of 623–698 K at various strain rates. After six passes of MDF, peak m-values of 0.45 and 0.46 were obtained at 648 K for Mg–1Gd and Mg–2Gd alloys, respectively, while for the Mg–3Gd alloy the peak m-value of 0.48 was achieved at a lower temperature of 623 K. According to the m-value of about 0.5 and the corresponding activation energies of 101–114 kJ/mol, the governing superplastic deformation mechanism was determined as grain boundary sliding (GBS) controlled by grain boundary diffusion.

The effect of molybdenum on clustering and precipitation behaviour of strip-cast steels containing niobium

Two high-strength low-alloy (HSLA) steels containing Nb-carbonitrides were produced, one contained Mo and the other was Mo-free. The alloys were produced by simulated direct strip casting, and were fully bainitic in the as-cast condition. Isothermal ageing treatments were carried out to precipitate harden the alloy, and the strength was measured using a shear punch test. The dislocation density was measured with X-ray diffraction (XRD), and was found to be larger in the alloy containing Mo in all ageing conditions. Atom probe tomography (APT) showed the presence of solute clusters in the as-cast condition, and the addition of Mo increased both size and volume fraction of these clusters. The solute clusters provided significant strengthening increments of up to 112 MPa, and cluster strengthening was larger in the Mo-containing alloy. Precipitation of Nb-carbonitrides was observed after longer ageing times, which were refined by the addition of Mo. This was attributed to the higher dislocation density that increased the number of nucleation sites. Precipitate chemistry was similar for both alloys, and contrary to some literature reports, minimal Mo was observed to segregate to the precipitates. A thermodynamic rationale is presented which describes the reasons that Mo segregates to the Nb-carbide in some alloys but not in others, despite the alloy chemistries being relatively similar.

Superplasticity in a multi-directionally forged Mg–Li–Zn alloy

Superplastic behavior of the Mg–8Li–1Zn alloy, processed by extrusion at 573 K followed by multi-directional forging (MDF) at 423 K, was studied using shear punch testing (SPT) of miniature specimens at various temperatures and strain rates. Microstructural analysis indicated moderate grain refinement, reducing the gran size from 8 μm in the initial as-extruded condition to 4 μm after 8 passes of MDF. Processing by MDF not only refined the grain structure but also provided a more homogeneous microstructure and a larger fraction of high-angle grain boundaries. SPT was performed at shear strain rates in the range of 3.3 × 10−3–1.3 × 10−1 s−1 and temperatures in the range of 498–573 K. The strain rate sensitivity (SRS) index (m-value), obtained from the slope of the central region of the sigmoidal shear stress–shear strain rate curves, was as high as 0.51 for the MDF processed material at 548 K. This is in contrast to the as-extruded material that exhibited a linear behavior with a maximum m-value of only 0.29 at the same temperature. For the MDF processed material, the activation energy of 61 kJ mol−1, which is close to 67 kJ mol−1 for the grain boundary diffusion in β-Li, and the high m-value of 0.51 suggest that the prevailing deformation mechanism is grain boundary sliding (GBS) controlled by grain boundary diffusion.

Effect of Zn addition on dynamic recrystallization behavior of Mg-2Gd alloy during high-temperature deformation

The effect of Zn/Gd ratio on dynamic recrystallization (DRX) of Mg–2Gd–xZn (x = 0, 1, 2 and 3 wt%) alloys was investigated by shear punch tests in the temperature range of 623–723 K and shear strain rate range of 1.0 × 10−2–1.2 × 10−1 s−1. It was observed that at low Zn/Gd ratio, excessive co-segregation of Gd and Zn solute atoms retards recrystallization and provides higher strength. At high Zn/Gd ratios, precipitation reduces the co-segregation, so that the alloy with Zn/Gd = 1.5, experienced the fastest DRX and the lowest strength. In addition, segregation resulted in a weaker texture, by elimination of nucleation and growth of the preferred orientations.

An Investigation on Microstructure Evolution, Mechanical Properties, and Strain Aging of Mg-1.8Zn-0.7Si-0.4Ca Biomedical Alloy Processed by Equal Channel Angular Pressing

The influence of equal channel angular pressing (ECAP) on microstructure and mechanical behavior, as well as, strain aging during ECAP and post-ECAP of Mg-1.8Zn-0.7Si-0.4Ca biomedical alloy was examined. The alloy in solid solution heat-treated condition was processed by ECAP with route BC at 350 and 400 °C. The specimens ECAPed at 350 °C were aged at 125 and 150 °C for different times. The hardness and shear punch test results indicated that performing ECAP at 350 °C for 4 passes increases the hardness and shear strength of the alloy from 48 HV and 110 MPa to 71 HV and 188 MPa, respectively. It was revealed that the average grain size of the alloy decreases from 78 µm to about 3 µm after 4 passes of ECAP. Three precipitates of CaMgSi, Ca2Mg6Zn3, and Mg2Si were detected in the solid solution specimen. After 4 passes of ECAP at 350 °C, Ca2Mg6Zn3 was completely dissolved and the morphology of Mg2Si changed from Chinese script to fiber-shaped particles. Dynamic strain aging occurred at high-temperature ECAP, and the specimens were overaged during post-ECAP aging. Small MgZn particles were detected in the overaged sample.

Processing of Al/Al2O3 Composite Using Simple Shear Extrusion (SSE) Manufactured by Powder Metallurgy (PM)

In this present study, Aluminum with 1, 3, 5 and 7 vol% alumina composites were produced via powder metallurgy and vacuum sintering techniques, then were followed by simple shear extrusion (SSE) process. Four SSE dies with different distortion angles (α) were used in experimental works. The SSE-ed samples with α = 22.5° and 30° were failed whereas the SSE-ed samples with α = 8° and 10° were deformed up to three passes, successfully. Porosity measurements were carried out by Archimedes method and microstructure evaluation of the specimens was accomplished using optical and scanning electron microscopy. Mechanical behavior of processed samples was investigated by shear punch test, and hardness measurements. It was understood that the SSE-ed samples have good bonding at aluminum/alumina interface. It was found that by increasing the number of SSE passes, ultimate shear strength and hardness were increased. The percentage of shear elongation and porosity content were decreased. Moreover, when the amount of α was increased, the shear strength for all samples was improved.

Evaluating the microstructure and mechanical properties of friction stir processed Al–Si alloy

ABSTRACTIn this study, mechanical behaviour and microstructural evolution in friction stir processing (FSP) of casting hypereutectic A390 aluminium alloy have been investigated. The mechanical behaviour of FSP samples was investigated by measuring the strain rate sensitivity using shear punch testing. The room-temperature shear punch tests were conducted at shear strain rates in the range of 10−4–10−1 s−1. The results indicate that the strain rate sensitivity index increases from about 0.015 to 0.120 for as-cast A390 after third FSP pass and then experiences a further growth in FSP passes. The increase in the grain size and CuAl2 intermetallic particle size result in a reduction in strain sensitivity index as well as shear strength after third FSP pass.

Effect of Zn content on hot deformation behavior of extruded Mg–Gd–Zn alloys

The effect of Zn content on the hot deformation behavior of Mg–2Gd–xZn (x = 0, 1, 2 and 3 wt%) alloys was studied by performing shear punch tests (SPT) in the temperature range of 623–723 K and shear strain rate range of 1.0 × 10−2–1.2 × 10−1 s−1. Arrhenius-type constitutive equations were employed to investigate the hot deformation behavior. It was found that addition of 1 wt% Zn yields the highest shear strength due to imposing higher solute drag pressure resulted from the co-segregation of Gd and Zn at grain boundaries and dislocations. Stress exponents of 2.7–5.5 and activation energies of 171–228 kJ mol−1 indicated that the main deformation mechanism is dislocation viscous glide with some contributions of dislocation climb and grain boundary sliding in various alloys. Finally, the optimum processing condition having the highest power dissipation efficiency was determined by developing processing maps. The microstructures of the safe and unsafe regions were associated with complete and partial dynamic recrystallization, respectively.

Finite element simulation of the residual stress in Ti6Al4V titanium alloy laser welded joint

AbstractIn this study, in order to investigate the mechanical heterogeneity of a Ti6Al4V titanium alloy laser-welded joint, microstructural examinations, microhardness tests and shear punch tests were carried out. Meanwhile, hole drilling was deployed to measure the residual stress in the joints. In residual stress simulation studies, the complex phenomenon of welding was numerically modelled by indirectly coupled transient, non-linear thermo-mechanical analysis. An elongated combined heat source was used here for modelling the temperature field. The effects of the residual stress after welding, both for considering and neglecting mechanical heterogeneity, were investigated systematically. The obtained results indicate that the residual stress of the simulation, when mechanical heterogeneity is considered closely, matches the experimental data.

The Correlation of Microstructure and Mechanical Properties of In-Situ Al-Mg2Si Cast Composite Processed by Equal Channel Angular Pressing.

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure and mechanical properties of hypereutectic Al-20%Mg2Si and Al-15%Mg2Si, as well as hypoeutectic Al-10%Mg2Si composites has been investigated. After fabricating the composites by in-situ casting, the composites were processed using the ECAP process up to two passes at room temperature. Microstructural studies have been carried out using a field emission scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. Mechanical properties were also documented using Vickers microhardness and shear punch tests. In the hypereutectic composites, a decrease in the average size of pro-eutectic Mg2Si (Mg2Sip) particles, breakages in eutectic networks, and lengthening of the Al (α) phase in direction of shear bands were observed after the ECAP process. For instance, the average size of Mg2Sip Particles in Al-20%Mg2Si composite reduced from 40 to 17 μm after 2 passes of ECAP. Furthermore, a uniform distribution of Mg2Sip particles was developed in the matrix. In hypoeutectic composite, the ECAP process caused a uniform distribution of eutectic Mg2Si (Mg2SiE) in the matrix that considered a favorable microstructure. Microhardness measurements and shear punch results showed an ascending trend after each pass of ECAP for all specimens. For example, microhardness and shear strength of Al-20%Mg2Si increased from 88 HV and 109 MPa to 119 HV and 249 MPa after two passes indicating 35% and 34% increments, respectively. Density and porosity calculations by Archimedes principle revealed that the density of the composites increased after two passes of ECAP due to the reduction of porosity.

Characterising and modelling the mechanical behaviour of polymeric foams under complex loading

Polymeric foams are used extensively as the core of sandwich structures in automotive and aerospace industries. Normally, several experiments are necessary to obtain the required properties to model the response of crushable foams using finite element analysis (FEA). Hence, this research aims to develop a simple and reliable calibration process for extracting the physical parameters which are required by the material model available in the commercial FE package Abaqus. To do this, a set of experimental tests, including uniaxial compression, uniaxial tension and shear punch tests, is proposed. All the experimental tests were also simulated, and generally, good correlations between experiments and numerical models were obtained. The validity of the overall approach was finally demonstrated using an indentation test in which the foam was subjected to a more complex mixed mode loading. During these indentation tests, digital image correlation was used to observe full-field strain distribution in the foam under the indenter. Good agreement between the experimental results and the numerical predictions was found for load–displacement response, failure mode and strain distribution.