Microstructural stages of intermetallic fracture during sheared deformation of AA6082 sheet

Abstract The progressive deformations of a shear band formation were studied to understand the fracture mechanism of AA6082(T6) sheets. The fracture characteristics of the alloys can be dictated by the intermetallic particles. Damage evolution of the alloy is quantitatively characterized as a function of strain. Larger, elongated, and favorably oriented particles fracture first (with initial deformation), and with progressive deformation (blanking), smaller and rounded particles start breaking. These broken particles become a crack nucleus for matrix cracking and coalescences. In the initial deformation stages, fragmentation of particles takes place without significant void growth. However, with subsequent deformation stages, the fragmentation process has been enhanced with multi-fragmentation and re-fracturing of previously broken particles. Larger particles nucleate voids at much lower strains with void growth. Crack has initiated in the shear band, preferably from the punch side (the punch side is sharper than the die side), and cracks are found almost parallel to the loading axis.


Introduction
AA6082 alloys have been extensively used in aviation and automotive sectors because of their good cast-ability, weld-ability, high strength-to-weight ratio, and good corrosion resistance.This is a wrought aluminum-magnesium-silicon alloy with several intermetallic phases present in the microstructure.The mechanical properties of the alloys are strongly influenced by their intermetallic particle's morphology, i.e., size, shape, and orientation (El-Rayes & El-Danaf, 2012;Guiglionda & Poole, 2002b;Yu et al., 2004).In various applications of aluminum alloys, the dominant damage micro-mechanism under different loading conditions is fracture and de-bonding of the silicon particles.Deformation and fracture of the alloy are usually associated with gradual microstructural damage accumulation (Wang et al., 2003;Yeh & Liu, 1996).Therefore, to understand the deformation and fracture behavior of AA6082 alloys, it is necessary to characterize and quantify the progressive evolution of microstructural damage (Guiglionda & Poole, 2002a;Su et al., 2010).
Previous studies on the damage evolution of intermetallic particles in Al-Si-Mg alloys only considered uniaxial tensile stress and were mostly qualitative in nature.Limited investigation reports are available on quantitative data, which shows the damage evolution of silicon particles as a function of tensile strain (Cowie et al., 1989;Hafiz & Kobayashi, 1994;Wang, 2003).
Experimental studies show that the distribution of intermetallic particles in aluminum alloys is inhomogeneous (Apps et al., 2002;McVeigh et al., 2007;Tekoğlu et al., 2015;Urreta et al., 2001;Van de Kasteele & Broek, 1977), both in terms of particle size and spacing.Void nucleation takes place through particle cracking or particle de-bonding during straining.The subsequent growth and coalescence of nucleated voids will finally trigger the ductile fracture (Caceres & Griffiths, 1996;Dighe et al., 2002;Dlouhý & Strnadel, 2008;Wang, 2004).Thomason et al. represented ductile fracture in terms of void nucleation, growth, and coalescences at percentage volume fractions of second phases (Thomason, 1993).Sudha Joseph et al. investigated the effects of strain, strain rate, temperature, and heat treatment on Si particles studied under compression.They observed that large and elongated particles are more susceptible to cracking (Joseph et al., 2013).Ming Li et al. studied the locations where fracture mode changes from shear to shear and tears.Large intermetallic particles initiate the unsteady progress of the fracture process (Li, 2000).Dighe et al. reported that the larger Si particles are more likely to undergo fracture and de-bonding (Dighe et al., 2000).Yeh and Liu observed that the fraction of broken Si particles increases with strain.Particle cracking is more gradual for finer structures and rapid for coarser ones [24].At higher strains, the adjoining particles are moving toward each other, which further accelerates the severity of the shear coalescence to create a shear instability inside the shear zone region (Hannard et al., 2018).Gurson and Kobayashi et al. presented the numerical model for void nucleation, which comprises the value of the particle area (volumetric) fraction (Gurson, 1976).Experimental background is of great importance for numerical analysis as intermetallic particles are responsible for providing sites for damage nucleation (Kobayashi & Dodd, 1989).
Cavity nucleation is a consequence of plastic deformation.At low temperatures, there is a value of critical plastic strain required to nucleate a cavity.Nucleation strain can be estimated using the model Brown and Stobbs proposed (Sandström, 2022).It also indicates that nucleation strain linearly increases with particle size (Sui et al., 2022).Limiting solutions for elastic-plastic deformation for rigid particles of both equiaxed and elongated shapes.Cavities are created from nondeformable second-phase particles at low-temperature ductile fracture (Wciślik & Pała, 2021).The concept of micro-void coalescence can be divided into three basic steps: nucleation, growth, and coalescence, with an emphasis on experimental work.To propose the fracture model, the local strain modeling is explicitly used (Fincato & Tsutsumi, 2022).The critical stress for void nucleation is enhanced due to reductions in the size of inclusion, level of strength, and embrittling species by increasing their bond strength.There are many reasons for void growth acceleration, and it may be due to an increase in inclusion size, initial voids, or increasing triaxiality (Xu et al., 2021).
However, despite the above-mentioned work on fracture through intermetallic particles, limited experimental work has been carried out on the progressive behavior of intermetallic particles.No work has been reported specifically for the blanking process, in which failure happens through the formation and propagation of the shear band.Also, there is no integrated quantitative approach to look at all aspects of microstructural evolution in the alloy and relate them to the fracture mechanism.
The current article reports the characterization of heterogeneous intermetallic particle distribution in the AA6082 sheet and their effect on the fracture behavior of intermetallic particles during the progressive deformation of shear band evolution.It also analyzes the effect of intermetallic particle size (D eq ), shape (aspect ratio), and angle orientation (θ) morphology.

Experimental work
Maintaining the material integrity of AA6082 sheets requires an understanding of the microstructural phases of intermetallic fracture during sheared deformation.Due to its exceptional strengthto-weight ratio, AA6082 is a popular aluminum alloy in a variety of industries, including the automotive and aerospace sectors.The alloy's intermetallic phases, such as AlFeSi and AlMgSi, can, however, have a considerable impact on the mechanical characteristics and fracture behavior under deformation.Investigating the microstructural phases of intermetallic fracture aids in pinpointing crucial failure causes and formulating plans to increase the effectiveness and dependability of the material.
For the analysis of the design failure of AA6082 sheet components, accurate intermetallic fracture prediction and prevention are essential.The microstructural stages of intermetallic fracture during sheared deformation can be studied to help researchers create simulation tools and predictive models that support the design process.In order to reduce the risk of intermetallic fracture and increase structural reliability, engineers can use these techniques to get insights into the stress distribution, crack initiation, and propagation routes.This allows them to optimize component shape, material selection, and manufacturing methods.

Chemical analysis
The present investigation was carried out using AA6082(T6) sheets.The composition of the alloy is indicated in Table 1.This is a wrought aluminium-magnesium-silicon alloy with particles of several intermetallic phases dispersed in the microstructure.

Blanking experiment
An experimental study was conducted on an aluminum sheet to evaluate the effect of progressive deformation on intermetallic particles.
Interrupted blanking tests were performed on a universal testing machine (UTM) (Zwick/Roell HA 100) at a quasi-static rate with a set of progressive deformations.
The interrupted blanking tests were carried out at various punch displacements on the alloy sheets.The samples were machined to a size of 50 mm × 50 mm.The actual tooling is shown in Figure 1.
A die with a fixed nominal diameter of 40 mm and a punch clearance of 0.075 mm (5% of sheet thickness, t) was chosen expressly for the blanking tools' design and fabrication.The edge radii of the punch and die were 0.13 mm and 0.25 mm, respectively.
Interrupted tests were conducted at five normalized punch displacements (punch displacement tʹ, normalized with the original sheet thickness t).The five normalized punch displacements were performed at 0.15t, 0.25t, 0.30t, 0.35t, and 0.45t, out of which SEM micrographs were shown for the starting (0.15 mm), middle (0.30 mm), and end (0.45 mm) and for the specimen that is completely sheared off.
After testing, partially fractured specimens were cut with a diamond cutter and electrodischarge machine (EDM) in order to reduce the damage and be used for further analysis.

Microstructural analysis
After an interrupted test on a UTM, partially sheared specimens were sectioned, mounted, polished, and etched (Vander Voort & Ltd, 2004).Step-by-step evolution of the microstructure of Fracture of large, elongated, and unfavorably oriented particles.
More particle fracture +Void formation.
Multi-fragmentation/Re-fracturing of Previously broken particles + Void growth.
Void coalescences and sample fracture.
the shear band was examined by Zeiss-made A×10 optical microscope (OM) and Zeiss Gemini 300 scanning electron microscope (SEM).A large set of high-resolution optical microscopy (OM) and SEM images were taken for analysis.
As shown in Figure 2, the total area of the shear band is approximately 2.1 × 10 3 µm 2 , the count of particles made from the 1100 μm2 area, considering at the center of the shear band.
The blanking process deforms the polycrystalline grains and shears the intermetallic particles present in the microstructure.This work looks at the quantitative evolution of these sheared intermetallic particles.
Particle distribution was quantified through the sheet thickness using image analysis.All the particles were measured over an area close to the center of the shear band.The particle distribution measurements were conducted on at least three images, with about 350 particles being considered per image.Quantification of intermetallic particles was performed by considering the nomenclature for four different stages of particle fracture, as discussed in the following section in detail.Identification of intermetallic phases was performed by means of Energy dispersive spectrography (EDAX) and X-ray diffraction (X-RD) analysis.

Results and discussion
SEM micrographs of as-received aluminum alloys reveal intermetallic particles of several shapes and sizes.
Increasing our understanding of how intermetallic phases affect the mechanical response and failure mechanisms of materials under challenging loading situations advances science.The results of this research can be extrapolated to other alloy systems, which will make it easier to create new materials with improved mechanical properties and increased resistance to intermetallic fracture for use in a variety of industrial applications.
E-DAX and X-RD analysis has been used to confirm that the as-received 6082(T6) alloys revealed five types of intermetallic compounds located at grain boundaries.Intermetallic phases are identified as α-Al 15 (FeMn) 3 Si, Al 9 Mn 3 Si, Mg 2 Si, Al 6 Mn, and AlFeSi.Those phases are generally present, according to E-DAX analysis, and in addition to Al, Si, and Mn, large levels of Fe are also present.SEM micrographs of as-received aluminum alloys reveal intermetallic particles of several shapes and sizes.
Typical intermetallic particl distribution in as-received conditions and with various deformation stages is depicted in Figure 3.It shows that the distribution of all intermetallic particles is strongly heterogeneous.
Figure 3 shows the SEM micrographs of shear band during progressive deformation for (a) asreceived, (b) 0.15t, (c) 0.30t, (d) 0.45t, and (e) a completely sheared specimen.To analyze the size effect, equivalent diameter (D eq ) of the particle was estimated.The D eq was defined as the diameter of a circle, equivalent to a given particle.
In Figure 3(a), as-received sample shows larger intermetallic particles.With progressive deformation, the size of these particles reduces, and their count will increase subsequently, as shown in Figure 3(b-d).An increase in imposed strain enhances the number of fractured particles.The particle size (D eq ) gets reduced with an increase in its distribution density.As seen in Figure 3(c,  d) for deformation at punch penetration 0.15t, particles were scattered randomly over the entire micrograph.However, the microstructure after 0.30t deformation shows that the particles in the shear band are aligned with the flow direction.This phenomenon is more pronounced as the deformation proceeds.Figure 3(e) shows a completely sheared-off specimen.Ductile fracture in this alloy is a result of void nucleation, growth, and coalescence, as shown in Figure 3.As observed, the particle size (D eq ) has reduced after 0.15t of deformation, and subsequently, voids get nucleated.It is related to particle fracture and fragmentation by means of void nucleation.The result of particle fragmentation is the geometrical change in particle size (D eq ) and their relevant aspect ratio (AR) and angle orientation (θ), as discussed below.(2) Voids (V) (Broken and pulled-out particles lead to voids formation).

Nomenclature of intermetallic particles
(3) Prior Unbroken Particles (PUP) (union of all the fragments and still combined with voids).
For simplicity in understanding of fracture evolution through intermetallic particles, they are classified into four classes with respect to progressive deformation.
In the context of intermetallic particles in AA6082(T6), "Prior Unbroken Particles" (PUP) are the nomenclature given to the intermetallic particles that have not been fragmented yet are still compact with the particle and void, but with further deformation, they will be fragment and become the fracture particles."Fracture Particle Fragments" (FPF) refer to different states of the particles after deformation or fracture.FPF have experienced fractures or deformations.When external forces or stresses exceed the strength of the particles, they can break into smaller pieces or undergo plastic deformation.These fragmented or deformed particles are referred to as FPFs.
In short, PUPs are intact intermetallic particles that have not been fractured or deformed, while FPFs are the result of fracture or deformation, representing broken or fragmented intermetallic particles within the AA6082(T6) alloy.The differentiation between PUPs and FPFs is essential for understanding the structural changes and mechanical properties of the material under specific conditions.High-resolution micrographs were obtained from SEM microscopy and performed using the image analysis software ImageJ.To quantify particle distribution, factors such as particle size (D eq ), shape (aspect ratio), and angle orientation (θ) were considered.
Figure 5 shows all sizes of unbroken particles that are present in a measured area of the shear band at a maximum deformation of 0.45t.All sizes (D eq ) of particles are present with different counts per unit area (/µm 2 ).The highest fractions (count/unit area) of Unbroken Particles (UBP) are in the range of 1.5-2 µm.

Effect of equivalent diameter (D eq )
Figure 6(a-d) shows the distributions of D eq of Unbroken particles (UBP), Voids (V), Prior unbroken particle (PUP), and Fracture particle fragment (FPF) with respect to progressive (punch) deformation in the rolling-thickness view plane.Figure 6(a) shows the measurement of only unbroken particles (UBP), i.e., equivalent diameter (D eq ) distribution.As shown in Figure 6(a), with an increase in the strain, the count per unit area of UBP decreases, and the peak shifts towards the smaller value of its D eq .This means particles are breaking continuously with an increase in the imposed strain.Figure 6(b) shows that the count of voids increases with an increase in strain.Void D eq shifts to the right side of the curve, i.e., toward larger D eq , with an increase in strain.There is no significant change in the count of voids for the deformation stages from 0.15t to 0.25t.
From Figure 6(a), it can be seen that particles are breaking at the deformation stages of 0.15t to 0.25t, but the void count does not change much for these deformation stages, as seen in Figure 6(b); this means that fragmentation of unbroken particles (UBP) is taking place without significant void growth for this particular deformation stage.For other deformation stages, there is a continuous decrease of unbroken particles (UBP), and an increase of voids (V) takes place with an increase in strain, as shown in Figure 6(a,b).
Figure 6(c) shows the equivalent size of the prior unbroken particles (PUP), which is a union of all the fragments and voids of a prior particle (Figure 4).Depending upon the prior particle size, a particle can break into several pieces (with voids in between), each piece separately called a fracture particle fragment (FPF), a measure shown in Figure 6(d).Since the prior unbroken particles (PUP) definition contains both fragmented particles and voids, it is a combined measure of fracture and void growth.Up to 50% of deformation occurs when these particles' equivalent diameter (D eq ) falls in the range of 2-4 µm.After 50% of deformation, D eq range has increased from 4 to 6 µm, and there is an increase in the equivalent diameter (D eq ) with imposed strain.
From deformation of 0.15t to 0.25t, there is an increase in breaking of larger size particles to a smaller size (Figure 6a); therefore, the count of fracture particle fragment (FPF) also increases (Figure 6d) when going from deformation of 0.15t to 0.25t.However, on further increase in strain, the broken particles further fragment to provide yet smaller fracture particle fragments (FPF) (Figure 6d).Thus, there is a change in the fracture mechanism from 0.25t onward, where multi-fragmentation and re-fracturing of previously broken particles are taking place.Qualitative and few quantitative analyses of fracture particles have been reported in the literature (Boselli et al., 1998;Mrówka-Nowotnik et al., 2007).Based on the above quantitative data, the particles fracture and void formation mechanism can be summarised as follows: (a) Initial Phase (up to 0.15t): Initial breaking of particles without a significant increase in voids.
In this phase, only the large particles are broken.
(b) Intermediate phase (0.15t-0.25t):In this phase, not only large but also smaller particles start to fracture.This phase is also characterized by a significant formation of voids.
(c) Final Phase (0.25t-0.45t):Re-fracturing and multi-fragmentation of already broken particles with large void growth.
(d) Fracture Phase (beyond 0.45t): In this stage, the various isolated voids coalescence, forming a large crack leading to sample fracture.

Effect of aspect ratio (AR)
Figure 7 shows the SEM micrograph for the prior unbroken particle (PUP) with major lengths "a", and minor lengths "b" and angle orientation "θ" of a particle with respect to the radial axis on the sheet plane.
From Figure 8, it is clear that the probability of fracture of a particle increases with an increase in the range of aspect ratio from 0.1 to 0.7.An aspect ratio much smaller than unity indicates elongated particles, while an aspect ratio closer to unity denotes more circular particles.Almost all the particles with an aspect ratio in the range of 0.1-0.7 will undergo fracture regardless of deformation conditions.This observation shows that larger and elongated particles are more prone to cracking and are consistent with previous observations (Lewandowski et al., 1989).Therefore, elongated particles are more effective in terms of initiation of fracture as compared to circular particles of the same equivalent size.Also, more circular particles require more deformation to break, while elongated particles can break down at a smaller deformation.

Effect of angle orientation (θ)
Figure 9 shows the variation of the orientation of prior unbroken particles (PUP) with respect to the loading axis.The prior unbroken particles (PUP) orientation angle varies from 0 to 90°.From deformation of 0.15t to 0.35t, there is no significant change in count per unit area, but as the deformation increases from 0.35t to 0.45t, there is a sudden increase in count per unit area for prior unbroken particles (PUP), as shown in Figure 9.
The probability of fracture is higher for particles oriented with their major axis nearly perpendicular to the loading axis.The deformation and loading within the shear band are simple shears.This is because of the plastic flow due to the compressive loading of the sample, which results in the shearing of the particle (Zhang et al., 1992).It is easier to cleave the particles along the minor axis than along the major axis.As a result of this, the cracks in the particles are also oriented in a narrow band of angles.
During the initiation of the formation of the shear band, particles are randomly oriented in all directions with an angle from 0 to 90° from the reference plane (as shown in Figure 9).After more than 50%t deformations, most of the prior unbroken particles (PUP) are oriented, with a maximum count ranging from 20° to 60°.It was observed that for prior unbroken particles (PUP), density decreases as the orientation angle deviates from 20° to 60°.
At a larger punch displacement, more particles are getting oriented at a smaller angle (θ), which indicates that more particles are aligned closer to the vertical axis.As within the shear band, more shear strain accumulates and the voids within would rotate to align with its length direction.

Evolution of prior unbroken particles (PUP)
Figure 10(a) shows the relationship between all four stages of nomenclature, i.e., unbroken particles (UBP), voids (V), prior unbroken particles (PUP), and fracture particle fragment (FPF).As the shear strain increases, there is an increase in voids (V) and prior unbroken particles (PUP).It is clearly visible from the diagram that, after the shear strain of 2, there is a drastic increase in fracture particle fragments (FPF).Similarly, from the same point, there is a drastic decrease in unbroken particles (UBP), so it shows that UBP and FPF are functions of shear strain.
From Figure 10(a), it is seen that beyond 2.4 strains, there is a sudden increase in the count of fracture particle fragments (FPF).This is strongly correlated with a decrease in unbroken particles (UBP) count at the same strain level.
Figure 10(b) shows that for particles that have an equivalent diameter (D eq ) less than 2 µm, there is no drastic change in count per unit area with the increase in percentage deformation over the entire strain range (only a slight increase in the count can be seen after 50% of deformation).However, for larger particles (D eq >2 µm), there is a significant increase in count per unit area with an increase in strain.Nonetheless, an increase in count per unit area with an increase in strain for the larger particles (D eq >2 µm) saturates at high strain.This indicates that the larger particles have a major contribution to the fracture in the shearing process throughout the deformation.

Figure 9. Angle orientations of prior unbroken particles (PUP).
From Figure 11(a), it can be seen that the mean of unbroken particles (UBP) decreases marginally, whereas the mean of voids increases gradually.Additionally, although the mean Deq of fracture particle fragment (FPF) decreases more gradually than the mean of prior unbroken particles (PUP), as shown, multiple fragmentations are happening as the imposed strain increases, and FPF is breaking down into smaller particles as the deformation progresses.Usually, larger particles nucleate voids at much lower strains than smaller particles, and void growth takes place more rapidly at larger particles, as shown in Figure 11(a).
The mean size of fracture particle fragments (FPF) decreases with an increase in the strain (Figure 11a).This supports the hypothesis that larger particles are first to fracture, and the extent of damage in the smaller particle size range gradually increases with strain.The volume fraction of the fracture particle fragment (FPF) increases drastically with an increase in strain.This nonlinear growth rate indicates a change of fracture mechanism at around 1.25 strains, as seen in Figure 11(b).

Particle cracking
Figure 12 shows the micrograph of cracking of particles from an interrupted test, at the deformation of 0.45t.It demonstrates the void growth process in the shear zone (Table 2).Note that the macroscopic cracks have not yet reached this region.Figure 12(a,b) presents the enlargement of a particular group of voids.Figure 12(c) depicts the process of void coalescence.
The nucleation of voids occurred by fragmentation and re-fragmentation of the particle-matrix interfaces.Usually, particles that have more equiaxed shape nucleate voids through interfacial decohesion, while particles with more irregular shapes and large aspect ratios often break through internal fragmentation, as shown in Figure 12(d).
As discussed earlier, the fracture in the blanking process can be summarised as shown in Table 2.

Crack initiation and propagation
Figure 13(a) shows the enlarged view of crack initiation and propagation in the shear band.Crack has initiated from the punch side, as in this case punch is sharper than the die.Cracks are found almost parallel to the loading axis.

Discussions and conclusions
A detailed microstructural analysis has been carried out to quantify the fracture evolution of intermetallic particles present in AA6082(T6) alloys as a function of strain.In asymmetric blanking (the punch side is sharper than the die side), cracks initiate in the shear band from the sharper (punch) side.Analysis of the experimental data leads to the following major conclusions on the fracture of particles and crack formation.
Several important implications may be reached by our work on the microstructural stages of intermetallic fracture during sheared deformation of the AA6082(T6) sheet: (1) Influence of the Intermetallic Phase: Our investigation reveals that intermetallic phases, such as AlFeSi and AlMgSi, play a substantial role in the fracture behavior of AA6082 sheets during sheared deformation, which is consistent with other studies (Ao et al., 2019;Kannan et al., 1998;Li & Arnberg, 2003;Smith et al., 2013;Zhang & Liu, 2020).As stress concentrators, these intermetallic particles cause crack initiation and growth along their borders.The one thing that was visible was larger, elongated, and unfavorably oriented particles fracture first (Initial phase), and with progressive deformation (blanking), smaller and rounded particles start breaking.
(2) Microstructural Evolution: This investigation indicates a consistent pattern of microstructural evolution during sheared deformation.Dislocation glide and pile-up occur during the initial deformation close to the intermetallic particles.Shear bands arise as a result of strain localization, which happens as deformation advances.These shear bands show a preference for alignment with the intermetallic phases, which promotes the beginning and growth of cracks.There is a change in the fracture mechanism (Final phase) with higher deformation, where multi-fragmentation and re-fracturing of previously broken particles are taking place, which enhances the fracture process.
(3) Failure Mechanisms: The findings show the coexistence of intergranular and transgranular fractures during the shearing deformation sheets.In areas with a high density of intermetallic particles, intergranular fracture is most common at grain boundaries.Within the aluminum matrix, there is a transgranular fracture that is frequently accompanied by the creation of shear bands and the spread of cracks across intermetallic phases.The broken particles become the crack nucleus for matrix cracking and coalescences.
(4) Shear Deformation Effects: Intermetallic fracture behavior in AA6082 sheets is significantly influenced by sheared deformation.Increased strain concentration caused by localized shear deformation encourages the start of intermetallic cracks and eventual fracture.Shear banding inside the aluminum matrix promotes the spread of intermetallic cracks, leading to a complicated fracture morphology.
(5) Practical consequences: Intermetallic failures can be reduced by optimizing alloy composition, heat treatments, and production conditions.Here techniques including grain refinement, intermetallic particle dispersion, and interfacial strengthening can improve the material's resistance to intermetallic fracture during sheared deformation.The shear fracture process can be summarized in four phases: (a) Initial phase, which shows the fracture of large, elongated, and unfavorably oriented particles; (b) Intermediate phase, which shows more particle fracture and void formation; (c) Final phase, which represents multifragmentation (re-fracturing) of previously broken particles with large void growth; and (d) Fracture phase, wherein finally void coalescences and sample fracture take place.
In conclusion, this investigation offers important new information about the influence of intermetallic phases, microstructural evolution, failure mechanisms, and shear deformation effects.These findings have implications for improving material performance and dependability in many industrial applications, as well as for a more comprehensive knowledge of intermetallic fracture behavior in AA6082 sheets.
Figure 1.A Set of punch and die, the actual model.

Figure 4
Figure 4(a,b) shows the schematic and actual nomenclature of particles, respectively, i.e., Figure 3. SEM images of the progressive evolution of intermetallic particles and voids during progressive deformation for (a) as-received, (b) 0.15t, (c) 0.30t, (d) 0.45t, and (e) completely sheared specimen, with respect to sheet thickness (t).
Figure 4. (a) Schematic representation of nomenclature for intermetallic particles.(b) Actual nomenclature for quantification of intermetallic particles.

Figure
Figure 5. Various microstructural stages of size (D eq ) distribution of unbroken particles (UBP) during 0.45 of deformation with respect to sheet thickness (t).
Figure 7. (a) SEM micrograph and (b) schematic showing prior unbroken particle (PUP) with major and minor lengths, particle orientation (θ), with respect to the radial axis on the sheet plane.
Figure 10.(A) The number of particles per unit area as a function of imposed shear strain.(b) Evolution of prior unbroken particles (PUP) with maximum (0.45 mm of punch penetration) deformation with respect to sheet thickness.
Figure 11.(A) Large diameter particles nucleate voids at much lower strains than smaller particles.(b) Drastic increase in volume fraction with respect to shear strain.

Figure
Figure 12.SEM micrograph showing (a, b. c, and d) particle cracking at maximum (0.45 mm of punch penetration) deformation.

Figure 13 .
Figure 13.Crack initiation and propagation at the shear band from the punch side.