Room Temperature Formability Research Articles

Development of a New Magnesium Alloy with Excellent Room Temperature Formability, Heat Dissipation, and Corrosion Resistance

Development of a New Magnesium Alloy with Excellent Room Temperature Formability, Heat Dissipation, and Corrosion Resistance

Orientation engineering of magnesium alloy: A review

Mg and its alloys have garnered significant attention due to their exceptional properties, including low density, good damping capacity, biocompatibility, recyclability, and high hydrogen storage capacity. These attributes position them as promising materials for applications in aerospace, transportation, electronics, and biomedical. The wrought Mg alloys, particularly in sheet form, are important materials for manufacturing lightweight structural components. However, their application is often constrained by relatively low room temperature formability. Preferred orientation, also known as texture, plays a crucial role in determining the plasticity and formability of Mg alloys. In this paper, we propose the concept of “orientation engineering”, which involves controlling the crystallographic orientation, thereby enhancing the plasticity and formability of Mg alloys. This review addresses two main aspects: firstly, it systematically explores how preferred orientation influences the plasticity and formability of Mg alloys, providing a foundation for orientation engineering. Secondly, it comprehensively introduces the development of methods to control grain orientation distribution, including alloying, pre-deformation, and asymmetric processing. This review might enhance the scientific understanding of orientation modification in Mg alloys and offer valuable guidance for future research on high-formability Mg alloys.

Microstructures, mechanical properties and damping performance of wrought Mg–Cu–Ca alloys

Mg–Cu–Ca alloy sheets show good room temperature formability and excellent thermal conductivity; however, their strength is insufficient for load-bearing applications. In this study, Mg–Cu–Ca ternary alloys were subjected to a conventional extrusion process, and the microstructures and tensile properties were systematically evaluated. The addition of extremely small amounts of Cu and Ca to pure Mg (Mg–0.03Cu–0.05Ca, wt%) led to significant refinement of dynamically recrystallized (DRXed) grains while preserving a certain fraction of un-DRXed grains, which contributed to a substantial increase in tensile yield strength. Adjusting the extrusion parameters further increased the tensile yield strength to 329MPa, driven by the combined effects of further refined DRXed grains and an increased area fraction of un-DRXed grains. The damping performance of the Mg–0.03Cu–0.05Ca alloy sheet was superior to that of commercial AZ31(Mg–3Al–1Zn–0.3Mn in wt%) alloy sheet but lower than that of pure Mg, particularly at low frequencies. This revealed that the solute segregation at grain boundaries plays a crucial role in the damping performance of Mg alloys.

Greatly improved room temperature formability of Al-Zn-Mg-Cu-Fe alloy sheets via coupling distribution of domains with different strengths

Using high strength Al-Zn-Mg-Cu-Fe alloy sheets as structural parts is capable of realizing lightweight of automobiles, but the low room temperature formability seriously limits their widespread use in automotive industry. In this study, we propose a new strategy to construct the coupling distribution of domains with different strengths by an innovate short-flow thermomechanical processing route. Both the compatible deformation capacity and room temperature formability of alloy sheets can be greatly enhanced by the coupling action of dislocations with domains. Finally, the average plastic strain (r̅-value) of alloys with a suitable coupling distribution of domains with different strengths can be greatly increased to 0.7171, which is a great outclass as those of traditional Al-Zn-Mg-Cu alloy sheets. Furthermore, the evolution mechanisms of domains with different strengths and the coupling action mechanisms of dislocations with domains have been discussed in detail.

Role of Al content on tensile properties and stretch formability of Mg–Al–Mn alloy sheet produced by continuous hot-rolling

Continuous rolling is a novel cost-effective process to fabricate high-performance Mg alloy sheets with good room-temperature formability, and we investigated the effect of Al content on tensile properties and room-temperature formability of a recently designed Mg–Al–Mn alloy sheet. An excellent combination of tensile 0.2 % proof stress (TPS) and limiting dome height (LDH) was achieved by adding the moderate content of Al (2 % or 4 %). The sheets annealed at a low temperature of 250 °C showed the TPSs of ∼170–180 MPa and LDHs of ∼8 mm. The LDHs further increased to ∼9 mm by the annealing at 350 °C, while moderate TPSs of ∼150–160 MPa were maintained. Further, the sheets had an in-plane isotropy in which the tensile properties along the rolling direction were very similar to those along the transverse direction. The good properties were achieved by fine grain structure with the reduced intensity of the (0001) poles. Indeed, the Elasto-ViscoPlastic Self-Consistent modeling revealed the increase of the activity of the prismatic slip by adding 4 % of Al, while it had a limited effect in improving the stretch formability. Further, we found that the deformation microstructure of the as-rolled sheets became uniform by the 2 % and 4 % Al addition, which would contribute to the reduced intensity of the (0001) poles after the annealing.

Improving the Room Temperature Formability of Magnesium AZ31B Alloy Sheets during the Incremental Sheet Forming Process

Improving the Room Temperature Formability of Magnesium AZ31B Alloy Sheets during the Incremental Sheet Forming Process

Twinning-induced texture weakening in Mg alloy and its consequent influence on ductility and formability

In this study, the room temperature formability of AZ31-0.5Ca was significantly enhanced by pre-deformation to 5% plastic strain. The pre-deformed samples showed the evolution of boundaries related to [Formula: see text] tension twins resulting in weakening of the strong basal texture and leading to excellent improvement in the formability. The pre-induced twining can be considered to be an effective approach to control the texture and enhance the formability of Mg alloy.

Developing a novel Mg[sbnd]2Zn[sbnd]3Li[sbnd]1Gd alloy sheet with high room-temperature formability by introducing an elliptical texture distribution

In recent years, modification of texture distribution has been considered a valid approach to improve the room-temperature (RT) formability of magnesium (Mg) alloys. In this study, a novel Mg2Zn3Li1Gd alloy sheet with weak elliptical-texture was fabricated by cold rolling and subsequent annealing, and it showed an excellent Erichsen (IE) value near 7.1 mm. Both quasi-in-situ electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis indicate that considerable basal and pyramidal dislocations can be activated in the cold rolling process. During annealing, these dislocations can induce nucleation and then cause preferential misorientation relationships around 〈uvt0〉 concerning the nuclei and parent grains, which can facilitate the formation of elliptical texture. Furthermore, the particle-stimulated nucleation (PSN) mechanism and the co-segregation of Zn and Gd at grain boundaries (GB) further weak texture intensity. Finally, the mechanical properties of the Mg2Zn3Li1Gd alloy sheet are significantly improved.

Optimized combination of room-temperature formability and high-temperature creep property in a dilute-alloyed Mg sheet via tailoring Nd solute segregation

The synergy of room-temperature formability and high-temperature creep property has been a long-term problem in the manufacturing of Mg alloy sheets. Aiming at saving rare-earth resource and providing a widely applicable approach to realize the synergy, this study focuses on the effects of preparation conditions on these two properties in Mg alloyed by dilute Nd (0.8 % in weight percent). Through comparing the mechanical behaviors of the samples prepared by different treatments, including low-temperature and long-time solution (Sample #1), high-temperature and short-time solution (Sample #2), and hot deformation for grain refinement (Sample #3), the best combination of stretch formability and creep property was successfully achieved in the Sample #1. The key reason was the conspicuous Nd solute segregation along grain boundaries after solution treated under the low-temperature and long-time condition. Such segregation behavior allowed dislocations moving freely in grain interiors but inhibited dislocations moving across grain boundaries. Finally, the stretch formability related to free dislocation slip in grain interiors and the creep property related to strong grain boundaries were synchronously enhanced. Thus, the low-temperature and long-time solution treatment is recommended for developing dilute Mg–Nd based alloy sheet used in the environment of alternating temperature changes.

CALPHAD-linked analysis of grain boundary segregation and phase-field simulation of solute-drag effect in multicomponent magnesium alloys

The application of Mg alloy sheets is currently limited owing to their poor room-temperature formability. The solute-drag effect is a potential mechanism via which the texture intensity of Mg alloys can be lowered to improve their formability. However, detailed analyses of the effects of solute–solute interactions on the solute drag in multicomponent systems are lacking. Herein, a CALPHAD-linked phase-field model was developed to evaluate the grain boundary segregation and solute-drag effects in a multicomponent system. The model was used to calculate the grain boundary segregation and solute drag in several Mg alloys, and the effect of solute–solute interactions on these phenomena was evaluated. The results showed that Zn and Ca mutually enhanced the grain boundary segregation in Mg alloys, leading to greater solute drag. However, the combination of Al and Zn mutually suppressed the grain boundary segregation and consequently, reduced the solute drag. These results support a previously proposed theory that Mg-Zn-Ca alloys exhibit strong solute drag owing to the co-addition of Zn and Ca, which reduces the texture intensity and improves the room-temperature formability. Furthermore, a new index for describing co-segregation and competitive segregation at grain boundaries, based on Hillert's grain boundary phase model, was introduced. The value of the index was calculated for various combinations of alloying elements in Mg alloys. The results showed that many ternary Mg alloys with a low texture intensity tended to co-segregate alloying elements.

Deformation Mechanisms of Magnesium Alloys with Rare-Earth and Zinc Additions under Plane Strain Compression.

The introduction of rare-earth (RE) elements into magnesium (Mg) alloys can significantly improve their ductility, thereby extending the applications of Mg products. However, the impacts of their chemical composition, temperature and processing methods on the mechanical properties of Mg products are highly debatable. In this work, we systematically investigate the deformation behaviors of Mg-Nd and Mg-Zn-Nd alloys using electron backscattered diffraction (EBSD) characterization. The samples were deformed to different stress levels to study the microstructure and texture development during channel die compression. The results reveal that the room temperature formability of the Mg-Nd alloy can be enhanced with the addition of Zn. This is attributed to the higher activities of prismatic slip and tensile twinning in the Mg-Zn-Nd alloy as compared to the binary counterpart, facilitating strain accommodation. When the strain increases, the growing and merging of the same twin variant rapidly consumes the parent grain, which is responsible for the texture modification from the transverse to the basal direction. At elevated temperatures, the twinning is suppressed in both alloys due to the decreased critical resolved shear stress of the non-basal slip systems. Additionally, an obvious sigmoidal yielding phenomenon is observed due to the multiple activation of the different deformation modes. These findings offer valuable insights into the evolution of the microstructure and texture during plane strain compression, elucidating the connections between material chemical composition, processing and mechanical properties, which are important for the advancement of Mg alloy application.

Exploring deformation mechanics of temperature assisted incremental forming with hybrid heating

The single point incremental forming (SPIF) process is a die-less rapid prototyping sheet metal forming method, extensively researched for over two decades. SPIF shows higher formability compared to conventional sheet forming methods. Deformation of materials such as magnesium (Mg) is favored at elevated temperatures due to their poor room temperature formability. Past studies have explored heat-assisted forming techniques to achieve improved formability in SPIF. However, the underlying mechanics of deformation is sparsely explored. The present work explores the mechanism of formability improvement based on thermal gradients for SPIF in hybrid heating. The SPIF experiments are conducted for a combination of local and global heating conditions achieved using tool contact friction and cartridge heaters. The local temperature, stress distributions, and limiting strains are obtained numerically. Fracture-forming limit diagrams (FFL) are developed, and numerical predictions are validated using experimental strain measurements under different forming conditions.

Texture Control Techniques for Improving Room Temperature Formability of Mg Alloys including Pre-twinning: A Review

Texture Control Techniques for Improving Room Temperature Formability of Mg Alloys including Pre-twinning: A Review

Warm Aging of Pre-aged AA6013 Sheet and Its Relevance to Room Temperature and Warm Forming Applications—Experimental and Modeling Analyses

AbstractWarm forming has been shown to be an effective way to increase the formability of various aluminum sheet alloys. If applied to precipitation hardenable alloys, aging and/or coarsening may occur during heating and/or forming processes. As such, there is a potential to leverage the warm forming process to artificially age precipitation hardenable alloys. In this study, the aging characteristics of a pre-aged Al-Mg-Si-Cu alloy (designated AA6013-PA and comprising a 4 h, 100 °C pre-aging cycle following solutionization) were examined using: (i) room temperature tensile and (ii) bendability experiments, as well as (iii) elevated temperature tensile and formability experiments in the temperature range of 220-280 °C. In the pre-aged condition, the alloy exhibited very high work hardening, elongation and bendability. It was found that T6-like properties can be obtained with short duration secondary aging of the AA6013-PA starting temper (410 s at 235 °C), followed by a paint bake cycle (30 min at 177 °C). In such heavily aged conditions, the bendability is found to be moderate and consistent with a T6 temper. Bendability of the pre-aged alloy is shown to be enhanced by reducing the extent of aging, which may be beneficial for applications requiring energy absorption during crash, for example. In the pre-aged condition, AA6013 displayed a 55% improvement in room temperature formability, relative to the T6 condition, for near plane-strain loading using a Nakazima punch, although neither temper exhibited formability improvements through warm forming. The aging kinetics of AA6013-PA were determined from mechanical test data and used to calibrate an aging kinetics model. A strong obstacle model was used to relate precipitation state to yield strength, for artificial aging in the range 220-280 °C. The incremental strength increase due to exposure to an automotive paint cure cycle was also modeled and found to yield accurate results. Warm deformation, as well as room temperature deformation, were shown to enhance the paint bake response of the alloy, reducing the time to the peak aged condition by up to 14% for artificial aging at 177 °C.

Insights into the microstructures and mechanical properties of magnesium–calcium–transition elements: A combined experimental and simulation study

Small amounts of transition elements: Ti, Mn, Fe, Co, and Ni, have been added to a Mg–0.1Ca (wt%) alloy to elucidate their additions on the microstructure and room temperature (RT) mechanical properties. Only Ni was effective in weakening the texture intensity and thus led to the improvement in RT formability and ductility, whereas the other elements were basically no effect. The microstructural characterization by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) in conjunction with energy-dispersive X-ray spectrometry (EDS) and numerical simulation using a grain boundary (GB) phase model indicates that the Ca and Ni co-segregated to the GB of the Ni-containing alloy, while the GB of the other alloys was enriched with Ca only. Further investigations by a correlative electron backscatter diffraction and STEM-EDS reveal that the transverse direction (TD) oriented GBs had significantly lower concentration of Ca and Ni compared to the basal-oriented GBs, which resulted in the development of the TD-split texture in the Ni-containing alloy. A compositionally optimized Mg–0.1Ca–0.1Ni (wt%) alloy showed a large index Erichsen value of 8.5 mm in the sheet form, and exhibited a high tensile yield strength of 238 MPa with a moderate fracture elongation of 14% in the form of an extruded rod. Due to the addition of small amounts of alloying elements, the newly developed Mg–0.1Ca–0.1Ni alloy had an excellent thermal conductivity of 154 W/(m·K) which is even higher than that of a commercial 5052 Al alloy.

Unveiling the Alloying-Processing-Microstructure Correlations in High-Formability Sheet Magnesium Alloys

Designing magnesium sheet alloys for room temperature (RT) forming is a challenge due to the limited deformation modes offered by the hexagonal close-packed crystal structure of magnesium. To overcome this challenge for lightweight applications, critical understanding of alloying-processing–microstructure relationship in magnesium alloys is needed. In this work, machine learning (ML) algorithms have been used to fundamentally understand the alloying-processing–microstructure correlations for RT formability in magnesium alloys. Three databases built from 135 data collected from the literature were trained using 10 commonly used machine learning models. The accuracy of the model is obviously improved with the increase in the number of features. The ML results were analyzed using advanced SHapley Additive exPlanations (SHAP) technique, and the formability descriptors are ranked as follows: (1) microstructure: texture intensity > grain size; (2) annealing processing: time > temperature; and (3) alloying elements: Ca > Zn > Al > Mn > Gd > Ce > Y > Ag > Zr > Si > Sc > Li > Cu > Nd. Overall, the texture intensity, annealing time and alloying Ca are the most important factors which can be used as a guide for high-formability sheet magnesium alloy design.

Improving the stretch formability of a heat-treatable magnesium–aluminum–calcium–manganese alloy by copper addition at the parts-per-million-level

Dilute magnesium–aluminum–calcium–manganese alloys have a quick age-hardening response and thus show higher strength after short periods of artificial aging; however, their room temperature formability is rather low. Here, we report that the addition of a small amount of copper (Cu) could substantially increase the Erichsen value of a Mg–0.5Al–0.5Ca–0.3Mn (wt.%) alloy due to the formation of a weakened sheet texture and variation in the distribution of (0002) basal pole figure. Specifically, the 0.03 wt% (300 parts-per-million) Cu-containing alloy showed a large index Erichsen value of 7.4 mm, which was noticeably higher than that of the Cu-free alloy (5.2 mm). Further investigation of the microstructure by transmission electron microscopy revealed that Cu co-segregated with Al and Ca at the grain boundaries, which played a critical role for the formation of the weaker basal texture and finer microstructure in the Cu-containing alloys. Owing to the small amount of the Cu addition, the resultant Mg–0.5Al–0.5Ca–0.3Mn–0.03Cu alloy showed a large thermal conductivity of 131 W/(m·K) in a solution treated condition. Subsequent artificial aging at 170 °C for 8 h (T6) not only improved the thermal conductivity to 141 W/(m·K) but also increased the tensile yield strength from 127 to 181 MPa. The improvement in both thermal conductivity and tensile yield strength by the T6-treatment is associated with the precipitation of densely distributed single-atomic layer Guinier–Preston zones lying parallel to the (0002) basal plane.

Does friction contribute to formability improvement using servo press?

Servo press forming machines are advanced forming systems that are capable of imparting interrupted punch motion, resulting in enhanced room temperature formability. The exact mechanism of the formability improvement is not yet established. The contribution of interrupted motion in the ductility improvement has been studied through stress relaxation phenomena in uniaxial tensile (UT) tests. However, the reason for improved formability observed when employing servo press is complicated due to the additional contribution from frictional effects. In the present work, an attempt is made to decouple the friction effect on formability improvement numerically. The improved formability is studied using a hole expansion test (HET). The limit of forming during hole expansion is modeled using the Hosford-Coulomb (HC) damage criteria, which is implemented as a user subroutine in a commercial explicit finite element (FE) software. Only the contribution of stress relaxation is accounted for in the evolution of the damage variable during interrupted loading. Therefore, the difference between simulation and experimental hole expansion ratio (HER) can be used to decouple the friction effect from the overall formability improvement during hole expansion. The improvement in HER due to stress relaxation and friction effect is different. The study showed that the model effectively captures the hole expansion deformation process in both monotonic and interrupted loading conditions. Compared to stress relaxation, friction effect played a major role during interrupted HET.

Investigation of flexible free incremental sheet forming (FFISF) process to form Ti6Al4V free-form surface panel at room temperature

Titanium alloy sheet metal shows promising applicability in the aerospace industry with excellent mechanical properties, while its limited room-temperature formability is essential to be improved by thermal-assisted methods, with expensive equipment and much energy consumption. In this work, the flexible free incremental sheet forming process is adopted to manufacture Ti6Al4V free-form surface panel at room temperature. The strain evolution and thickness distribution during this new process are also analysed through finite element methods to reveal the deformation mechanism. Experimental and simulated results show that this process has potential advantages in rapidly fabricating low-ductility sheet metal with complex shapes at room temperature by improving strain and thickness distributions.

Effect of Post-Heat Treatment Temperature on Interfacial Mechanical Properties of Cold-Rolled Ti/Al Clad Material.

Titanium and titanium alloys possess low density, high specific strength, and excellent corrosion resistance, but are expensive and have low formability at room temperature. Therefore, to reduce cost and achieve excellent properties, titanium and titanium alloys are jointed with aluminum and its alloys, which are inexpensive and have low density and excellent room temperature formability. Cladding is a widely used solid-state bonding technique, and the post-heat treatment of titanium/aluminum clad materials is required to improve their interfacial properties, which is important to ensure the reliability of Ti/Al-clad materials. The interfacial properties of Ti/Al-clad materials are significantly affected by changes in the microstructure and mechanical properties after the post-heat treatment. Thus, in this study, the relationship between the microstructure and mechanical properties at the interface of Ti/Al-clad materials was analyzed after the post-heat treatment at several different temperatures. The thick diffusion and intermetallic compound layer was formed with post-heat treatment owing to the active diffusion of Al atoms. As a result, their uniaxial and nanomechanical properties were varied with the interfacial characteristics of the Ti/Al-clad material.