Fatigue crack nucleation in as-cast AA6082 remains insufficiently resolved at the microstructural scale, particularly regarding how localized strain and slip-system interactions at grain boundaries and triple junctions govern nucleation. This study aims to document the local conditions that lead to crack nucleation, to identify microstructural regions of strain localization, and to evaluate their role in the earliest stages of fatigue damage. Full-field digital image correlation (DIC) was employed under cyclic loading to quantify localized deformation, while complementary electron backscatter diffraction (EBSD) provided crystallographic context through grain orientation, Schmid-factor mapping and local strain incompatibilities. The analysis incorporated 3D representations and angular metrics to evaluate geometric (in)compatibility among potentially active slip systems across neighboring grains, with emphasis on triple junctions. Regions of elevated local deformation frequently coincided with grains of high Schmid factor; however, fatigue crack nucleation occurred only when geometric compatibility was lacking among the possible active slip systems. An extensive study of a fatigue nucleation site reveals that the possible active slip systems in the surrounding grains at the triple junction lack geometric compatibility. By combining DIC and EBSD, the proposed method establishes a practical framework for describing microscale deformation behavior, clarifies the mechanisms of early crack nucleation in as-cast AA6082, and provides a generalizable approach for other alloys. The approach also enables a statistical perspective based on the probability of critical, geometrically incompatible configurations, informing microstructure-aware fatigue design.

The present study was performed on an Al-6

The present study was carried out on B319 alloy modified with about 180 ppm Sr. To this alloy, Ca (0–500ppm) and Bi (0.1–1.0%) were added. Their deleterious effects on the eutectic Si characteristics (as-cast and solution heat-treated conditions) as well as tensile properties under the same conditions plus T6 temper were investigated. The results show that Ca addition up to 500 ppm leads to partial modification, whereas applying 0.1%Bi causes almost complete un-modified structure. Further addition of Bi has no marked effect. Calcium–Mg and Bi–Mg interactions would lead to a significant deterioration in the three tensile parameters of the base B319 alloy, i.e., 30 MPa and 60 MPa in UTS (T6 temper) for 0.05%Ca and 1.0%Bi additions, respectively, about 45 MPa in YS, and almost 100% in ductility (no improvement). Apparently, B319 alloy containing less than 100 ppm Ca or about 0.5%Bi produces the best Q values in the solution heat treated and the T6 conditions. The main fracture behavior of these alloys was the formation of fine dimple structure with Ca or Bi particles imbedded at their interiors.

The addition of small but effective amounts of free-machining elements to Al–Si casting alloys significantly improves the machinability of these alloys. These added elements, which are softer and have a lower melting point than the matrix alloy, form as small globules dispersed in the microstructure of the aluminum casting. In this form, the dispersed phase of low-melting elements promotes chip-breaking and helps to lubricate the cutting tool. The Al-11%Si-Cu-Mg alloys studied were mechanically tested in order to acquire an understanding of the effects of additives on the tensile properties under the same alloy conditions used for preparing the machinability test blocks. Drilling operations were carried out using a high-speed machining center under fixed cutting conditions. The machinability characteristics of these alloys were evaluated by examining the drilling forces and moments, tool life, and chip shape in each case. Results show that the addition of 0.15wt% Sn has a beneficial effect on the tool life of carbide drills, which may be ascribed to the precipitation of small and uniformly distributed β -Sn particles having a low melting point. Lead is not a suitable choice as an additive because of environmental concerns. Bismuth also has several detrimental effects associated with its presence in the Al–Si alloys, including the formation of the high melting point Bi 2 Mg 3 phase, and the interaction of Bi with Sr, which is mainly added/required for Si modification. Thus, of the free-machining elements tested, Sn is the most promising in the context of improving the alloy machinability and mechanical properties.

The purpose of this study is to investigate the potential of zirconium (Zr) and nickel (Ni) in enhancing the strength of 319-type cast alloys at high temperature. The high-temperature testing was performed on tensile bars either in the as cast or T6 tempered (190 °C/2h) condition. High-temperature tensile tests were performed at 25, 190, 250 and 300 °C. Tensile bars were held at each temperature for 10h prior to pulling to fracture. The results revealed that (Al,Si)3(Zr,Ti), Al3CuNi, Al65Si16Ni13 or Al4SiNi and Al9NiFe phases are the main features in the microstructures of alloys containing Zr and Ni. In addition, other phases containing Cu such as Al5Fe2Cu2, AlSiFeNiZrCu (probably Al4SiNi (Cu, Fe, Zr) or Al4SiNi with traces of Cu, Fe, Zr), and Q-Al5Cu2Mg8Si6 could also be formed. All these phases result in depletion in the Cu content and hence reduction in the alloy strength. Both Al2Cu and Al3Zr are the hardening phases during artificial aging. The tensile properties were plotted as a function of aging temperature and in the form of Q-charts. The fracture behavior of selected samples was examined as well, using FESEM microscopy.

The influence of the trace elements Pb, Bi, and Sn on the microstructure and mechanical properties of Sr-modified and grain-refined Al-10.8

The present study was performed on A356 and A413 alloys containing (6–11) %Si. Measured amounts of high-purity La and Ce were added to the molten metal that was allowed thereafter to solidify at a slow rate (~ 0.8 °C/s). The results show that the addition of RE metals (La + Ce) up to 3 wt% leads to an increase in the freezing range through an increase in the melting point of the non-modified alloys by 12 °C, with a decrease in the Al–Si eutectic temperature, by 8 °C, respectively, at 3 wt% addition, regardless of the alloy Si content. Although 0.2% Ce is sufficient to drop the Te2 by about 6 °C, 1.5% Ce is required to raise the Tα2 by about 8–10 °C, regardless of the alloy composition. In the case of A413 alloy, eutectic undercooling was only observed in the non-modified base alloy. In the case of alloys modified with Sr, the presence of Sr neutralizes the effect of RE on the freezing range due to its reaction with RE. Addition of La up to 1.5% has no significant effect on the increase in either Tα2 or Te2 compared to that caused by the addition of the same amount of Ce. The increase in the freezing range with the addition of RE metals leads to the formation of a marked amount of shrinkage porosity, in particular in modified alloys. Due to the high affinity of Sr for oxidation, the porosity observed in Sr-modified alloys is twice as much as that in the non-modified alloys, on account of the porosity resulting from the presence of SrO films, in addition to that from shrinkage porosity resulting from the RE metal addition. The main RE-based intermetallics are: Al–RE–Ti, Al–RE–Si, Al–RE–TR–Si (TR = transition metals). In high Si-containing alloy, i.e., 413 alloy, Al–Re–Si compound was frequently observed.

This article discuss the effects of heat treatment and lubrication modes on the machinability of an A356 alloy (Al-Si-Mg); the alloy is studied as-received, with solution heat-treated alloy (SHT) as well as with an alloy that is solution heat-treated and then aged at 155, 180 and 220 °C. In the course of machinability evaluation, several criteria including cutting force, surface roughness, tool wears and burr analysis (chip) were studied. The results and analysis in this work indicated that the selected machinability criteria are important and necessary to effectively evaluate the machinability of A356 alloys. The machinability of both materials and tools were estimated in terms of cutting force, chip thickness ratio and burr formation, flank wear and roughness. The effects of different cutting parameters (cutting speed and feed rate) and lubrication modes (dry, mist and wet) on the machinability of the A356 cast alloy were also examined. The influence of heat treatments on the burr formation and surface quality was clearly revealed by the experimental results. Experimental work revealed that cutting forces were influenced significantly by aging and cutting speed. However, the different aging at 155, 180, and 220 °C and the cutting speed significantly affected the machinability of the A356 cast alloy. The results obtained show that a better drilling performance in terms of surface quality occurs at a high feed rate, with dry drilling and artificial aging at T6.

In this study, the results pertaining to the influence of various metallurgical parameters on the tensile properties of Al–Si–Cu–Mg 354-type casting alloys are presented. This is discussed with an emphasis on acquiring an insight regarding the mechanical limits of Al–Si–Cu–Mg 354-type alloys in the context of these parameters, and to obtain an understanding of the effects of the addition of nickel and/or zirconium on alloy 354 with respect to the mechanical properties obtained at high temperature (155 °C and 300 °C for holding times at temperature ranging from 10 to 100 h). Based on an analysis of the results obtained, the following conclusions may be drawn. The results show that additions of Zr and Zr + Ni increase the high-temperature tensile properties, in particular for the alloy containing 0.2 wt% Zr + 0.2 wt% Ni, which exhibits an increase of more than 30% in the tensile properties at 300 °C compared with the base 354 alloy. In other words, the addition of 0.4 wt% Ni + 0.4 wt% Zr to the 354 alloy is not sufficient to resist softening at 300 °C/100 h (cf. UTS: 52 MPa, YS: 45 MPa, %El: 23% with UTS: 361 MPa, YS: 343 MPa, %El 1.23%, observed after T6 treatment). The addition of 0.4 wt% Ni to alloy 354 leads to a decrease in the tensile properties, compared to the base alloy. This decrease may be attributed to a Ni–Cu reaction which could interfere with the formation of the Al2Cu strengthening precipitates, thereby affecting the age hardening process. As a consequence, percentage elongation increases with the testing temperature, from as-cast to T6-treated samples tested at high temperature (155 °C and 300 °C, respectively). In summary, the best high-temperature tensile properties are displayed by the alloy containing 0.2 wt% Zr + 0.2 wt% Ni.

The first part of this work was to explore the development of residual stresses in I-4 and V-6 engine blocks made of B319.1 alloy using the sectioning technique. The results suggest that there is refinement in the microstructure due to an increase in cooling rate along the cylinder. The developed residual stresses were found to be tensile for both I-4 and V-6 engine blocks. Furthermore, the variation in the developed residual stresses was found to be insignificant. The results also indicate that air cooling produced the highest residual stresses compared to warm water and cold water quenching. Solution heat treatment and freezing (−30 ºC) led to the maximum amount of residual stress relaxation where 50% of the residual stresses were reduced after the solution heat treatment step. Aging time and aging temperature are directly proportional to the residual stress relaxation. Correlations between alloy hardness and the evolved residual stress have been established. In the second part, residual stresses were obtained from the milled surface of a rectangular workpiece (30 × 172 × 302 mm, five blocks/alloy for five studied alloys). Thirteen layers of material were removed from each block, where each layer consisted of ten paths, and the depth of cut was 1.35 mm, using fresh and dull inserts. In this case, measurement of residual stresses was carried out on the blocks at the end of the milling process, using the X-ray technique. All stresses were of tension-type compared to compression type in the un-machined shoulders. Due to the high applied forces required when using dull inserts, the resulting residual stresses were almost twice that generated by new inserts in spite of the large difference in the machining distance.

The present research work aimed at evaluating the effect of Ce and La rare earth (RE) additions on the formation of intermetallics in an Al-8.0Si-2.4Cu-0.4Mg-0.4Fe-0.6Mn-0.15Ti alloy (coded D0). These alloys were solidified at a rate of ~0.7°C/s. Microstructural analyses revealed the presence of two types of RE-containing intermetallic phases: (i) a gray phase with a fixed composition of Al21Ti2RE(Ce/La) and (ii) a white RE-containing intermetallic phase stemming from the reaction of the RE (Ce/La) with Si, Fe, and Cu. The present study aimed as well at studying the influence of the additions of Ce and La elements (0–1.0%) on the high-temperature (250 °C) tensile properties of the Al-8.0Si-2.4Cu-alloys. The results showed that T6-treated alloys, Sr-modified alloys, or those containing Ce/La exhibited UTS values comparable to the solution heat-treated, T5, and T7 alloys.

In the current study, a series of forty-two cast Al–Si–Cu–Mg -based alloys with additions of transition metals (V, Cr, Ni) and rare earth (RE) metals (La, Ce) were prepared and mechanically tested in the as-cast, T5, T6 and T7 heat treatment conditions. The microstructures were investigated using optical microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The volume fraction, aspect ratio, and roundness of second phase constituents were determined by ImageJ analysis software. The microstructural observations show that the RE elements have a greater impact on the microstructure of cast alloys, resulting in the formation of new types of intermetallic phases containing RE, Al–Si–Cu–RE and Al–Ti–RE. With regard to the mechanical properties, it was found that the highest strength of the casting alloys was found with 0–0.2 wt% addition of Ce/La. However, the addition of more than 0.2 wt% induced a detrimental effect on the mechanical properties due to precipitation of a high volume fraction of insoluble intermetallic compounds containing RE. Excessive addition of RE elements leads to the formation of a coarse intermetallic compound along the grain boundary. Besides, RE elements have a marginal modification effect in terms of changing the morphology of the eutectic Si particles.

The effect of laser wave modes on the fatigue behavior of laser cold-wire welding made of 4.8 mm thick AA6005-T6 aluminum alloy was investigated using continuous and pulsed wave lasers. Due to the inherent differences in these two wave laser modes, different welding parameters were used, while keeping the interaction time constant. The mechanical properties of welded joints were measured using tensile tests, while their fatigue performances were quantified using a constant amplitude force-controlled technique to obtain S-N curves. The pulsed wave laser mode produced higher fatigue resistance as compared to the continuous wave mode. The fatigue strength corresponding to the run-out condition (i.e., 107 cycles, in this study) was about 28% higher for the pulsed wave mode than for the continuous wave laser mode. At a high stress amplitude (30 MPa), the lifespan of the pulsed wave joints was about twice as high as that with continuous wave joints. These fatigue results were cross-referenced with a 3D topographic map, a 2D microhardness map, a metallographic study, and a fractographic analysis to better understand the crack nucleation and crack propagation mechanisms. A microhardness analysis performed along the cross-section of the joints did not reveal any significant difference between pulsed wave and continuous wave modes. A fractographic analysis confirmed crack propagation within the fusion zone and that 83 to 90% of cracks nucleated from the root undercuts. Topographic maps of the joints before fracture revealed that the continuous wave laser mode produces deeper and narrower (i.e., more acute) undercut defects than does the pulsed wave mode. A Weibull approach based on the biggest defects found on the fracture surfaces also confirmed that the continuous wave process produces larger defects at the root. Top defects are significantly small (55%), but they have a larger size dispersion than do root defects. Since the root undercuts act as the main stress concentrators, they are mainly responsible for the lower fatigue performance of the joints, and their sizes and shapes should be minimized during further process development of the welding process.

The work presented here was carried out on an Al-6%Cu-0.7%Si alloy (used in as cast, T5 and T7 aged conditions), in comparison with B319.0 (T7 by treated at the two places where treatment appears) and A356.0 (T6 treatment) alloys. Wet milling was carried out on 15 blocks of each alloy using new inserts for 120-m machining distance. A total of 75 blocks were employed. The results show that the cutting forces for the Al-Cu based alloys are not affected by the applied heat treatment. The presence of Cu in the B319.0 neutralized, to some extent, the harmful effect of the hard Si particles. Maximum cutting forces were obtained from machining the A356.0 alloy treated in the T6 condition, due to the presence of a high density of hard eutectic Si particles (~ 41500 particles/mm2), in addition to the dense precipitation of ultra-fine Mg2Si particles. Thus, the presence of 6%Cu in the Al-Cu-based alloy may act as a self-lubricant leading to much smoother finishing surfaces compared with those exhibited by B319.0 and A356.0 alloys. Similar observations were reported on the wearing of the drilling tools. Moreover, after 120-m machining distance, tiny burrs were found adhered to the outer edges of the workpiece, whereas burrs in the case of the A356.0 alloy were separated from the block.

The present study was performed on an Al-6% Cu-0.7%Si alloy, and 319 and 356 alloys following different heat treatments. The main task was to evaluate the drilling and tapping characteristics of the Al-Cu alloy with respect to the Al-Si-based 319 and 356 alloys. The drilling work was carried out on a Huron K2X8five CNC machine at 15,000 rpm with continuous cooling to absorb the heat and to clean the holes from the chips formed during the drilling operation. The results show that the addition of Si coupled with T6 aging treatment produces the highest cutting forces (about 360 N) among the alloys studied (approximately 270 N) after 2500 holes. Considering the Al-Cu-based alloys, varying the aging treatment has practically no significant bearing on the cutting forces. Apparently, a high Cu content acts as a self-lubricant, facilitating the drilling process up to 2700 holes, with no sign of tool wear. However, due to the low level of Si in the Al-Cu-based alloy, built up edge (BUE) is more frequent, with conical chips, which would affect the precision of the size of the drilled hole. The chips are normally dull and characterized by their rough surfaces compared to those obtained from A356.0 alloy. Tapping of the drilled holes was carried out using Guhring 971 H6 M6 6HX- HSSE taps. The HT200-based alloys revealed excellent machinability with no sign of tool wearing after 2500 holes. In contrast, the tool failed after 1600 holes in the case of 356 alloy and 2160 holes for 319 alloy. Thus, it is concluded that the presence of 3.5% Cu in the 319 alloy helped in reducing the severity of wearing due to eutectic Si particles. However, the tapping forces reached 120 N prior to failure compared to about 75 N in the case of T200-based alloys.

The fatigue properties of gas metal arc welded and friction stir welded assemblies made of aluminum alloy AA6061-T6 structural extrusions were examined. The mechanical performances of welded joints were obtained using uniaxial tensile and force-controlled constant amplitude axial fatigue tests. Microstructural and fractographic analyses were conducted to document the influence of the process on microstructure evolution, fatigue crack initiation sites, and propagation mechanisms leading to the final rupture of the assemblies. Microhardness measurements and digital image correlation techniques paired with interrupted tensile tests were also used to investigate the complex heterogeneous local mechanical behavior and to highlight the fact that the crack initiation mechanism was driven by the microstructural state of the joint as well as by the structural-contact-fretting occurring at the notch root. The corresponding fatigue strengths at 2 million and 10 million cycles were evaluated respectively at 10% and 20% higher for friction stir welded assemblies versus gas metal arc welded assemblies. Fractographic analyses revealed that the fatigue cracks were initiated from microstructural features (pores for the GMAW configuration and banded structure on the crown side for the FSW configuration), or from large sub-surface grains in a shallow region below the structural-contact-fretting occurring at the notch root.

In the present research an appropriate tool design is developed for joining of AA2198-T3 and AA2024-T3, subsequently the influence of rotational and traverse speed for the selected tool on the joint tensile properties is evaluated. Three shoulder profiles (flat, spiral, and fan) and five different pin profiles (tapered cylindrical, straight cylindrical, threaded cylindrical, cone, and square) were designed. The weld quality has been evaluated by means of visual inspection, microstructure analysis and tensile tests. Local strain maps measurements using Digital Image Correlation (DIC) enabled to determine weld local properties and determine the joints failure mode during monotonic tensile loading test. Two dimensional hardness map across the cross section through the weld joint was also carried out to further document the heterogeneities of the FSW joint. The tapered cylindrical pin with a fan shoulder was the optimal tool design configuration in terms of mechanical properties. Tensile tests were conducted on the joints produced by optimal tool design at different traverse and rotational speeds. The fracture of samples occurred in the HAZ of the advancing side (AA2198) and in the middle of the joint, which are zones depicting the highest strain values and the lowest hardness values via DIC technique and micro hardness measurements, respectively. Higher traverse speed was found to increase the joint yield strength. The joint efficiency can reach up to 78% by choosing optimum welding speed parameters of 750 rpmand 450 mm/min. Besides, it has been found that although the rotational speed has not a significant effect on the mechanical properties, higher rotational and traverse speeds can enhance the formation of tunneling and kissing bond defects in the joint.

The local mechanical properties of a dissimilar friction stir welded AA-2024-T3/AA-2198-T3 joint were documented during a uniaxial tensile test. High-resolution digital image correlation was performed during monotonic tensile tests to capture the local in-plane strain fields of the heterogeneous macrostructure of the weld. In the shoulder-affected region, banded macrostructures with heterogeneous mechanical properties were found. They were related to pronounced textures regions, which can be associated to strain-rate gradient during one rotation of the tool. The banded macrostructures in the nugget region were observed to be responsible for early plasticity in the joint and ultimately to be the fracture location of the weld. The heterogeneous mechanical response of the joint was also investigated by microhardness measurements. Differences were found between hardness and local tensile properties, demonstrating microhardness measurements can be misleading and only direct high-resolution digital image correlation techniques can document the mechanical behavior of materials having complex and heterogeneous micro-/macrostructures.

In industry, the sliding mechanical systems are subject to friction and wear phenomena. These phenomena can be the origin of a reduction of the efficiency of the mechanical system even to be responsible for its incapacity. Generally, the materials of the parts which are moving relative (tribological couple) of these systems are low alloy steels and carbon steels, thanks to their good mechanical and tribological properties. The present work aimed to study, the surface wear and damage induced by dry sliding of hard carbon steel AISI 1055 (disc) against tempered low alloy steel AISI 4140 (pin) with different hardness and applied loads was investigated. The results revealed that the interaction between the applied load and pin hardness result in complex thermo-mechanical behaviour of the worn surfaces. When a lower hardness pin is used, the main wear mechanisms observed on the discs were abrasion, adhesion, and oxidation. When a higher hardness pin is used, the wear of the discs is governed by delamination, oxidation, and plastic deformation. In particular, third-body wear occurs at high applied load resulting in higher wear rate of high hardness pins compared to low hardness pins.