Multilayer Mg–Stainless Steel Sheets,Twinning and Texture Evolution

In the present study, different combinations of multilayer sheets were prepared from 1 and 2 mm Mg AZ31 along with 0.25, 0.5, and 1 mm 304 L stainless steel. The texture and microstructure of the elongated samples (20 and 30 pct strain) were studied. It was found that the transversal stress plays an important role in both texture evolution and twinning in these composites. The obtained pole figures revealed an axial texture tilt with increasing steel layer volume fraction (V _f). It was found that this is a direct effect of transverse stress, which becomes more significant upon reducing Mg V _f. This extra stress component tilts the basal planes away from the original normal direction in monolithic samples. Moreover, our results indicate that with decreasing Mg V _f, twinning activity was increased in the 20 pct deformed samples but reduced in the samples with 30 pct elongation. It is known that at high strains where sufficient transverse stress is generated, the activity of prismatic slip is significantly enhanced, which promotes the motion of dislocations and reduces the necessity of twinning. With decreasing Mg V _f, stronger transversal stress is generated and Mg reaches the critical threshold of prismatic activity at lower strains.

     

Selective Oxidation and Reactive Wetting of 1.0 Pct Si-0.5 Pct Al and 1.5 Pct Si TRIP-Assisted Steels

Heat treatments were performed using an isothermal bainitic transformation (IBT) temperature compatible with continuous hot-dip galvanizing on two high Al–low Si transformation induced plasticity (TRIP)-assisted steels. Both steels had 0.2 wt pct C and 1.5 wt pct Mn; one had 1.5 wt pct Al and the other had 1 wt pct Al and 0.5 wt pct Si. Two different intercritical annealing (IA) temperatures were used, resulting in intercritical microstructures of 50 pct ferrite (α)-50 pct austenite (γ) and 65 pct α-35 pct γ. Using the IBT temperature of 465 °C, five IBT times were tested: 4, 30, 60, 90, and 120 seconds. Increasing the IBT time resulted in a decrease in the ultimate tensile strength (UTS) and an increase in the uniform elongation, yield strength, and yield point elongation. The uniform elongation was higher when using the 50 pct α-50 pct γ IA temperature when compared to the 65 pct α-35 pct γ IA temperature. The best combinations of strength and ductility and their corresponding heat treatments were as follows: a tensile strength of 895 MPa and uniform elongation of 0.26 for the 1.5 pct Al TRIP steel at the 50 pct γ IA temperature and 90-second IBT time; a tensile strength of 880 MPa and uniform elongation of 0.27 for the 1.5 pct Al TRIP steel at the 50 pct γ IA temperature and 120-second IBT time; and a tensile strength of 1009 MPa and uniform elongation of 0.22 for the 1 pct Al-0.5 pct Si TRIP steel at the 50 pct γ IA temperature and 120-second IBT time.     

Effect of Cold Rolling on as–ECAP Interstitial Free Steel

Ti-stabilized interstitial free steel subjected to eight passes, route B_C room temperature equal channel angular pressing (ECAP) additionally was cold rolled (CR) up to 95 pct thickness reduction. Electron back-scattering diffraction and transmission electron microscopy characterized microstructural refinement and microtexture evolution, whereas the mechanical properties were assessed by uniaxial tensile tests. After 95 pct CR, the average high-angle grain boundary spacing reduces to 0.14 μm, whereas the high-angle boundary fraction increases to ~81 pct. The ECAP negative simple shear texture components rotate by ~15 deg around the transverse direction toward the rolling direction for up to 50 pct CR, with typical rolling textures observed at 95 pct CR. The decrease in boundary spacing produces a ~500 MPa gain in 0.2 pct proof stress, a ~600 MPa increase in ultimate tensile strength (UTS), and a ~4 pct loss in total elongation after 95 pct CR. Similar rates of decrease in work hardening correspond to comparable rates of cross and/or multiple slip events irrespective of the processing regime and substructural refinement. The fracture mode of the tensile samples changes from ductile to brittle type between ECAP and 95 pct CR and is attributed to the reduced work hardening capacity of the latter. The modified Hall–Petch equation shows that the convergence of high-angle boundary spacing values with their low-angle counterparts results in an increased contribution via boundary strengthening to the 0.2 pct proof stress and UTS.     

The Mechanism of High Strength-Ductility Steel Produced by a Novel Quenching-Partitioning-Tempering Process and the Mechanical Stability of Retained Austenite at Elevated Temperatures

The designed steel of Fe-0.25C-1.5Mn-1.2Si-1.5Ni-0.05Nb (wt pct) treated by a novel quenching-partitioning-tempering (Q-P-T) process demonstrates an excellent product of strength and elongation (PSE) at deformed temperatures from 298 K to 573 K (25 °C to 300 °C) and shows a maximum value of PSE (over 27,000 MPa pct) at 473 K (200 °C). The results fitted by the exponent decay law indicate that the retained austenite fraction with strain at a deformed temperature of 473 K (200 °C) decreases slower than that at 298 K (25 °C); namely, the transformation induced plasticity (TRIP) effect occurs in a larger strain range at 473 K (200 °C) than at 298 K (25 °C), showing better mechanical stability. The work-hardening exponent curves of Q-P-T steel further indicate that the largest plateau before necking appears at the deformed temperature of 473 K (200 °C), showing the maximum TRIP effect, which is due to the mechanical stability of considerable retained austenite. The microstructural characterization reveals that the high strength of Q-P-T steels results from dislocation-type martensite laths and dispersively distributed fcc NbC or hcp ε-carbides in martensite matrix, while excellent ductility is attributed to the TRIP effect produced by considerable retained austenite.     

Role of Microstructure and Temperature on the Tensile Fracture Behavior of Oxide Dispersion Strengthened 18Cr Ferritic Steel

The tensile fracture behavior of oxide dispersion strengthened 18Cr (ODS-18Cr) ferritic steels milled for varying times was studied along with the oxide-free 18Cr steel (NODS) at 25, 200, 400, 600, and 800 °C. At all the test temperatures, the strengths of ODS–18Cr steels increased and total elongation decreased with the duration of milling time. Oxide dispersed 18Cr steel with optimum milling exhibited enhanced yield strength of 156 pct at room temperature and 300 pct at 800 °C when compared to oxide-free 18Cr steel. The ductility values of ODS-18Cr steels are in the range 20 to 35 pct for a temperature range 25 to 800 °C, whereas NODS alloy exhibited higher ductility of 37 to 82 pct. The enhanced strength of ODS steels when compared to oxide-free steel is due to the development of ultrafine grained structure along with nanosized dispersion of complex oxide particles. While the pre-necking elongation decreased with increasing temperature and milling time, post-necking elongation showed no change with the test temperature. Fractographic examination of both ODS and NODS 18Cr steel fractured tensile samples, revealed that the failure was in ductile fracture mode with distinct neck and shear lip formation for all milling times and at all test temperatures. The fracture mechanism is in general followed the sequence; microvoid nucleation at second phase particles, void growth and coalescence. The quantified dimple sizes and numbers per unit area were found to be in linear relation with the size and number density of dispersoids. It is clearly evident that even nanosized dispersoids acted as sites for microvoid nucleation at larger strains and assisted in dimple rupture.

     

Fracture behavior of thixoformed 357-T5 Al alloys

The effects of microstructural features on the fracture behaviors, including impact, high-cycle fatigue, fatigue crack propagation, and stress corrosion cracking, of thixoformed 357-T5 (Al-7 pct Si-0.6 pct Mg) alloy were examined. The resistance to impact and high-cycle fatigue of thixoformed 357-T5 tended to improve greatly with increasing volume fraction of primary α. An almost threefold increase in impact energy value was, for example, observed with increasing volume fraction of primary α from 59 to 70 pct. The improvement in both impact and fatigue properties of thixoformed 357-T5 with increasing volume fraction of primary α in the present study appears to be related to the magnitude of stress concentration at the interface between primary α and eutectic phase, by which the fracture process is largely influenced. The higher volume fraction of primary α was also beneficial for improving the resistance to stress corrosion cracking (SCC) in 3.5 pct NaCl solution. The in-situ slow strain rate test results of thixoformed 357-T5 in air and 3.5 pct NaCl solution at various applied potential values demonstrated that the percent change in tensile elongation with exposure decreased linearly with increasing volume fraction of primary α within the range studied in the present study. Based on the fractographic and micrographic observations, the mechanism associated with the beneficial effect of high volume fraction of primary α in thixoformed 357-T5 alloy was discussed.     

Mechanical Properties and Microstructural Characterization of Cu-4.3 Pct Sn Fabricated by Selective Laser Melting

Components were fabricated via selective laser melting (SLM) of prealloyed Cu-4.3 pct Sn powder and heat treated at 873 K and 1173 K (600 °C and 900 °C) for 1 hour. Tensile testing, conductivity measurement, and detailed microstructural characterization were carried out on samples in the as-printed and heat-treated conditions. Optimization of build parameters resulted in samples with around 97 pct density with a yield strength of 274 MPa, an electrical conductivity of 24.1 pct IACS, and an elongation of 5.6 pct. Heat treatment resulted in lower yield strength with significant increases in ductility due to recrystallization and a decrease in dislocation density. Tensile sample geometry and surface finish also showed a significant effect on measured yield strength but a negligible change in measured ductility. Microstructural characterization indicated that grains primarily grow epitaxially with a submicron cellular solidification substructure. Nanometer scale tin dioxide particles identified via X-ray diffraction were found throughout the structure in the tin-rich intercellular regions.

     

Fracture behavior of thixoformed 357-T5 Al alloys

The effects of microstructural features on the fracture behaviors, including impact, high-cycle fatigue, fatigue crack propagation, and stress corrosion cracking, of thixoformed 357-T5 (Al-7 pct Si-0.6 pct Mg) alloy were examined. The resistance to impact and high-cycle fatigue of thixoformed 357-T5 tended to improve greatly with increasing volume fraction of primary α. An almost threefold increase in impact energy value was, for example, o served with increasing volume fraction of primary α from 59 to 70 pct. The improvement in both impact and fatigue properties of thixoformed 357-T5 with increasing volume fraction of primary α in the present study appears to be related to the magnitude of stress concentration at the interface between primary α and eutectic phase, by which the fracture process is largely influenced. The higher volume fraction of primary α was also beneficial for improving the resistance to stress corrosion cracking (SCC) in 3.5 pct NaCl solution. The in-situ slow strain rate test results of thix oformed 357-T5 in air and 3.5 pct NaCl solution at various applied potential values demonstrated that the percent change in tesile elongation with exposure decreased linearly with increasing volume fraction of primary α within the range studied in the present study. Based on the fractographic and micrographic observations, the mechanism associated with the beneficial effect of high volume fraction of primary α in thixoformed 375-T5 alloy was discussed.     

High Strength and High Ductility of Ultrafine-Grained,Interstitial-Free Steel Produced by ECAE and Annealing

Interstitial-free steel (IF steel) underwent severe plastic deformation by equal-channel angular extrusion/pressing (ECAE/P) to improve its strength, and then it was annealed to achieve a good strength-ductility balance. The coarse-grained microstructure of IF steel was refined down to the submicron level after eight-pass ECAE. The ultrafine-grained (UFG) microstructure with high dislocation density brought about substantially improved strength but limited tensile ductility. The limited ductility was attributed to the small, uniform elongation caused by early plastic instability. The annealing at temperatures below 723 K (450 °C) for 1 hour did not lead to remarkable softening, whereas annealing at temperatures up to 923 K (650 °C) resulted in complete softening depending on the development of recrystallization. Therefore, the temperature of approximately 923 K (650 °C) can be considered as a critical recrystallization temperature for UFG IF steel. The annealing at 873 K (600 °C) for different time intervals resulted in different stress–strain response. Uniform tensile elongation increased at the expense of strength with annealing time intervals. After annealing at 873 K (600 °C) for 60 minutes, the yield strength, tensile strength, uniform elongation, and total elongation were found to be 320 MPa, 485 MPa, 15.1 pct, and 33.7 pct, respectively, showing the better combination of strength and ductility compared with cold-rolled samples.     

A theoretical model for the flow behavior of commercial dual-phase steels containing metastable retained austenite: Part II. calculation of flow curves

The role of metastable retained austenite(γ _R), its volume fraction, and mechanical stability on the flow characteristics of a dual phase steel containing 20 vol pct of ‘as quenched’ martensite in a ferrite matrix has been examined in this paper employing the flow curve expressions derived in Part I of this paper. It has been found that for a given volume fraction ofγ _R, its mechanical stability plays a crucial role in enhancing the ductility. Whereas highly stableγ _R does not contribute either to strength or ductility of the steel, highly unstableγ _R which causes an increase in the strength is detrimental to ductility. Aγ _R which is moderately stable and undergoesγ _R → α′ transformation over a larger strain range is beneficial to enhanced ductility. Increasing amounts of moderately stableγ _R significantly increase both the strength and the ductility of dual-phase steels through a sustained work-hardening due toγ _R → α′ transformation. Load transfer which is determined by a parameterq has a significant contribution to work-hardening. A value of ∣|q∣|= 4500 MPa has been found to partition realistically the stress and strain in these steels.     

Recovery of Ductility in Ultrafine-Grained Low-Carbon Steel Processed Through Equal-Channel Angular Pressing Followed by Cold Rolling and Flash Annealing

The low-carbon steel workpieces are deformed by equal-channel angular pressing at 293 K (20 °C) up to an equivalent strain of ~12 using route B _c, which results in the bulk ultrafine-grained (UFG) structure with high dislocation density and partial dissolution of cementite. The yield strength (YS) is enhanced from 208 (as-received) to 872 MPa and the tensile strength is increased from 362 to 996 MPa, but the material loses total elongation (TE) from 36.2 to 2.9 pct. Cold rolling of equal-channel angular pressed steel produces the refined structure of grain size 0.11 μm. The YS increases further to 924 MPa with a marginal gain in ductility due to the reappearance of the γ fiber component. Flash annealing the samples, which were equal-channel angular pressed followed by cold rolling, at 873 K (600 °C) results in 27 pct of micron-sized (9 µm) ferrite grains in submicron-sized (<1 µm) matrix with a reduced defect density and small amount of precipitation of cementite. TE increases from 2.9 to 23.3 pct. The material retains a YS of 484 MPa and tensile strength of 517 MPa, which are higher than those of the as-received material. The UFG grains are failed by cleavage, but the micron-sized grains display ductile fracture. The ductility of the flash-annealed material is recovered significantly due to bimodal grain size distribution in ferrite and the development of a good amount of γ fiber texture components. The major contribution toward recovery of ductility comes from the bimodal grain size distribution in ferrite rather the precipitation of cementite.

     

The Investigation of Strain-Induced Martensite Reverse Transformation in AISI 304 Austenitic Stainless Steel

This paper presents a comprehensive study on the strain-induced martensitic transformation and reversion transformation of the strain-induced martensite in AISI 304 stainless steel using a number of complementary techniques such as dilatometry, calorimetry, magnetometry, and in-situ X-ray diffraction, coupled with high-resolution microstructural transmission Kikuchi diffraction analysis. Tensile deformation was applied at temperatures between room temperature and 213 K (−60 °C) in order to obtain a different volume fraction of strain-induced martensite (up to ~70 pct). The volume fraction of the strain-induced martensite, measured by the magnetometric method, was correlated with the total elongation, hardness, and linear thermal expansion coefficient. The thermal expansion coefficient, as well as the hardness of the strain-induced martensitic phase was evaluated. The in-situ thermal treatment experiments showed unusual changes in the kinetics of the reverse transformation (α′ → γ). The X-ray diffraction analysis revealed that the reverse transformation may be stress assisted—strains inherited from the martensitic transformation may increase its kinetics at the lower annealing temperature range. More importantly, the transmission Kikuchi diffraction measurements showed that the reverse transformation of the strain-induced martensite proceeds through a displacive, diffusionless mechanism, maintaining the Kurdjumov–Sachs crystallographic relationship between the martensite and the reverted austenite. This finding is in contradiction to the results reported by other researchers for a similar alloy composition.

     

Microstructure-Based FEM Modeling of Phase Transformation During Quenching of Large-Size Steel Forgings

The current investigation encompasses the development of a microstructure-based 3D finite element model (FEM) of water quenching process of large-size, high-strength steel forgings with accurate predictions of the volume fraction of phases. The approach is based on modified TTT/CCT curves that consider a lower martensite start temperature value. An experimental procedure consisting in the validation of the FEM simulations was conducted using high-resolution dilatometry, optical and scanning electron microscopy, and instrumentation of a large-size steel block with several thermocouples at different locations. Results showed a very good agreement between the temperature predictions of the 3D FEM model and those obtained from direct measurement of instrumented forged block with an average error of about 1 pct in the quarter region. The volume fraction of phases and hardness distribution across the block were also predicted by the proposed 3D FEM model. The numerical results revealed bainitic volume fractions of about 74 pct at the center of the block and about 91 pct in the quarter region. These predictions were also confirmed by dilatometry test and metallographic examination of the microstructure. Micro hardness measurements were conducted on dilatometry samples that simulate the heat treatment cycle of different thicknesses of the forged block were compared with those predicted by the FEM, and very good agreements were obtained, further confirming the validity of the simulations. The proposed procedure in this research improves the quality of predictions by increasing the reliability of material parameters such as TTT optimization and accurate determination of thermo-physical parameters.

     

Influence of the precipitate-free zone width on the tensile properties of an Al-6 Wt pct Zn-1.2 Wt pct Mg alloy

The mechanical properties of an Al-6 wt pct Zn-1.2 wt pct Mg alloy with various width of precipitate-free zones have been investigated. The width of the precipitate-free zone (PFZ) has been changed by the quench interruption technique without any appreciable change in the size and distribution of precipitates. An important relationship has been observed between the width of the PFZ and the quench-interruption period;i.e., the width of the PFZ increases in proportion to the square root of the holding time at 200°C. From the analysis of stress-strain curves as well as the observation of dislocation arrangements in slightly deformed specimens, the plastic deformation has been found to occur preferentially in the PFZ. The initial stage of deformation is much affected by the change in the width of the PFZ, but in the later stage, the work-hardening rate seems to be almost independent of the PFZ width. Tensile tests show that the ultimate tensile strength and the 0.2 pct proof stress decrease very little with increasing width of the PFZ, while the uniform elongation is practically constant regardless of the reduction in the nonuniform elongation. The work-hardening rate at the initial stage of deformation is found to decrease in proportion to the reciprocal of the PFZ width. This relationship can be explained from the dislocation model for work hardening.     

Enhanced Mechanical Properties in a Low-Carbon Ultrafine Grain Steel by Niobium Addition

The microstructure and mechanical behavior of low-carbon ultrafine grain steel (UFG; 0.165 wt pct carbon) after niobium (Nb) addition were investigated. It was found that the addition of 0.028 wt pct of Nb resulted in the optimal tensile strength of 990.8 MPa with an adequate elongation of 15.5 pct. In comparison to the normal UFG steel (without Nb), the strength of Nb-UFG steel was substantially enhanced without any sacrifice of its elongation. The main increased strengthening mechanisms of Nb-UFG steel were precipitation and dislocation strengthening. The improved work hardening and adequate elongation of Nb-UFG steel could be ascribed to geometrically necessary dislocations and heterogeneous ferrite grains. Discontinuous static recrystallization occurred by a small rolling reduction on hardened martensite laths, resulting in the formation of heterogeneous ferrite grains. Ultrafine ferrite grains were surrounded by high-angle grain boundaries, and nanoscale Nb(C, N) carbonitrides providing precipitation strengthening were precipitated mainly in the α-phase.

     

Breakdown Trade-Off Relation of Mechanical Properties via Micro-alloying in Mg–Mn Alloys

The impact of micro-alloying on tensile behavior at strain rates in various ranges is examined using five types of extruded Mg-0.3 at. pct Mn–0.1 at. pct X ternary alloys, where X is selected as a common element, Al, Li, Sn, Y or Zn. Microstructural observations reveal that the average grain size of these extruded alloys is between 1 and 3 μm, and these micro-alloying elements segregate at grain boundaries. In room temperature tensile and compression tests, these results show that the mechanical properties and deformation behavior are influenced by the micro-alloying element, even as a small addition of 0.1 at. pct. Mg–Mn–Y and Mg–Mn-Zn alloys show higher strength and smaller strain rate sensitivity (m-value) among the present alloys, owing to the rate-controlling mechanism as dislocation slip. On the other hand, the Mg–Mn–Li alloy exhibits the largest elongation to failure in tension and the highest strain rate sensitivity, associated with high contribution of grain boundary sliding to deformation. These differences are due to the grain boundary segregation of the micro-alloying elements. Compared to the common Mg alloys, the present ternary alloys also show a trade-off relationship between strength and ductility, which is similar to that of the well-known Mg alloys; however, these properties of the Mg–Mn system ternary alloys could be controlled via the type of micro-alloying elements with a chemical content of 0.1 at. pct.

     

Effects of AlN Nanoparticles on the Microstructure,Solderability, and Mechanical Properties of Sn-Ag-Cu Solder

The addition of nanosized AlN particles to Sn-3.0 wt pctAg-0.5 wt pctCu (SAC305) lead-free solder alloy has been investigated. The various weight fractions of AlN (0, 0.03, 0.12, 0.21, 0.60 wt pct) have been dispersed in SAC305 solder matrix by a mechanical mixing and melting route. The influences of AlN nanosized particles on the microstructure, mechanical properties, and solderability (e.g., spreadability and wettability) have been carried out. The structural and morphological features of the nanocomposite solder were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscope (TEM). The experimental results show that the best combination of solderability and mechanical properties is obtained at 0.21 wt pct AlN in the solder matrix. The reinforced composite solder with 0.21 wt pct AlN nanoparticles shows ≈25 pct improvement in ultimate tensile strength (UTS), and ≈4 pct increase in the spreadability. In addition, the results of microstructural analyses of composite solders indicate that the nanocomposite solder, especially reinforced with 0.21 wt pct of AlN nanoparticles, exhibits better microstructure and improved elongation percentage, compared with the monolithic SAC305 solder.

     

Stress Corrosion Behavior of Low-temperature Liquid-Nitrided 316 Austenitic Stainless Steel in a Sour Environment

Low-temperature nitridation is a widely used surface heat treatment. Low-temperature liquid nitridation was applied to 316 austenitic stainless steel and an S-phase (expanded austenite) layer was achieved on the alloy surface. The effect of the S-phase layer on corrosion resistance and stress corrosion cracking was investigated in a sour environment. When a bending stress of 164 MPa (80 pct yield stress, YS) was applied, no macroscopic corrosion cracking and pits were observed on the nitrided samples and the S-phase layer stayed intact. Although no macroscopic corrosion cracking was observed on the non-nitrided samples under 205 MPa (100 pct YS), some pits were formed on the alloy surface. This could be attributed to the high stresses and hardness, and the excellent corrosion resistance of the S-phase layer introduced by low-temperature nitridation. Supersaturated nitrogen atoms in the S-phase layer can effectively prevent the decrease in pH of the corrosive medium and accelerate the alloy repassivation kinetics. However, when the bending stress was increased to 205 and 246 MPa (100 pct YS, 120 pct YS), macroscopic cracks were observed in the presence of both tensile stress and a corrosive medium.

     

Microstructure and Mechanical Properties of a High-Strength Ti-4Al-2Fe-3Cu Alloy Fabricated by Sintering and Hot Extrusion

A Ti-4Al-2Fe-3Cu (wt pct) alloy containing only low-cost alloying elements was fabricated by vacuum sintering a blend of TiH₂, Al, Fe, and Cu powders at 1200 °C for 1 hour followed by hot extrusion at the same temperature. The as-extruded alloy exhibited a microstructure consisting of mainly α/β lamellar colonies and Ti₂Cu as a minor phase. The average colony size and lamella thickness were 118 and 12 µm, respectively, and Fe and Cu were predominantly distributed in the β lamellae. The as-extruded alloy had a high tensile yield strength (YS) and ultimate tensile strength (UTS) of 1248 and 1270 MPa, respectively, but a limited ductility (elongation to fracture: 2.3 pct). Annealing at 750 °C for 4 hour caused the average colony size and lamella thickness of the alloy to increase to 145 and 17 µm, respectively, and the volume fraction of the β phase decreased with the annealing. These microstructural changes resulted in a slight decrease of the YS and UTS to 1221 and 1253 MPa, but a clear increase of the ductility with the elongation to fracture reaching 4 pct. This work demonstrates that a combination of relatively low-temperature vacuum sintering, hot extrusion, and annealing can be effectively utilized to fabricate a low-cost Ti-4Al-2Fe-3Cu alloy with high strength and appreciable tensile ductility.

     

Serrated Flow and Enhanced Ductility in Coarse-Grained Al-Mg Alloys

Conventionally, superplasticity requires the presence of a fine-grained microstructure to enable grain-boundary sliding to take place during deformation. However, coarse-grained materials have also been shown to exhibit higher than normal amounts of ductility, provided they possess a high-enough strain rate sensitivity. In this work, coarse-grained Al-3 pct Mg, Al-5 pct Mg, and AA 5056 alloys were tested for enhanced ductility. The dependence of flow stress on temperature was found to display some unusual characteristics; these were interpreted as resulting from the occurrence of dynamic strain aging (DSA). In these materials, a local peak in elongation coincided with the presence of an unusual peak in rate sensitivity. This region of higher than normal rate sensitivity was coupled with the usual region of negative rate sensitivity found in DSA-prone materials, such as the Al-Mg alloys. A maximum ductility of 170 pct was recorded at 723 K (450 °C) and a strain rate of 5 × 10⁻² seconds⁻¹ was found in the vicinity of the rate sensitivity peak. This was found to increase to nearly 300 pct when the gage length was shortened. These peaks in elongation occurred below the maximum test temperatures.