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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. [ABSTRACT FROM AUTHOR]

Strength and ductility synergy in an Mg-3mass%Al-Mn (AM30) alloy sheet was successfully improved via twin-roll casting and annealing at low-temperature. An AM30 alloy sheet produced by twin-roll casting, homogenization, hot-rolling, and subsequent annealing at 170 °C for 64 h exhibits a good 0.2% proof stress of 170 MPa and a large elongation to failure of 33.1% along the rolling direction. The sheet also shows in-plane isotropic tensile properties, and the 0.2% proof stress and elongation to failure along the transverse direction are 176 MPa and 35.5%, respectively. Though the sheet produced by direct-chill casting also shows moderate strengths if the annealing condition is same, the direct-chill casting leads to the deteriorated elongation to failure of 23.9% and 30.0% for the rolling and transverse directions, respectively. As well as such excellent tensile properties, a high room-temperature stretch formability with an Index Erichsen value of 8.3 mm could be obtained in the twin-roll cast sheet annealed at 170 °C for 64 h. The annealing at a higher temperature further improves the stretch formability; however, this results in the decrease of the tensile properties. Microstructure characterization reveals that the excellent combination of strengths, ductility, and stretch formability in the twin-roll cast sheet annealed at the low-temperature annealing is mainly attributed to the uniform recrystallized microstructure, fine grain size, and circular distribution of (0001) poles away from the normal direction of the sheet.

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.

• Twin-roll casting leads to the formation of uniform and fine grain structures. • The microstructure feature is effective to improve strengths-ductility synergy. • In-plane isotropic tensile property and good RT formability have been obtained. Strength and ductility synergy in an Mg-3mass%Al-Mn (AM30) alloy sheet was successfully improved via twin-roll casting and annealing at low-temperature. An AM30 alloy sheet produced by twin-roll casting, homogenization, hot-rolling, and subsequent annealing at 170 °C for 64 h exhibits a good 0.2% proof stress of 170 MPa and a large elongation to failure of 33.1% along the rolling direction. The sheet also shows in-plane isotropic tensile properties, and the 0.2% proof stress and elongation to failure along the transverse direction are 176 MPa and 35.5%, respectively. Though the sheet produced by direct-chill casting also shows moderate strengths if the annealing condition is same, the direct-chill casting leads to the deteriorated elongation to failure of 23.9% and 30.0% for the rolling and transverse directions, respectively. As well as such excellent tensile properties, a high room-temperature stretch formability with an Index Erichsen value of 8.3 mm could be obtained in the twin-roll cast sheet annealed at 170 °C for 64 h. The annealing at a higher temperature further improves the stretch formability; however, this results in the decrease of the tensile properties. Microstructure characterization reveals that the excellent combination of strengths, ductility, and stretch formability in the twin-roll cast sheet annealed at the low-temperature annealing is mainly attributed to the uniform recrystallized microstructure, fine grain size, and circular distribution of (0001) poles away from the normal direction of the sheet. [ABSTRACT FROM AUTHOR]

We have successfully developed a Mg–3Al–0.4Mn (wt%) alloy sheet with good room-temperature formability. The alloy sheet shows a large Index Erichsen value of 8.2 mm due to its unique texture feature where the most of the grains have circular distribution of basal poles away from the normal direction of the sheet. The fine grain structure also leads to moderate strengths and large ductility with in-plane isotropic tensile property. These mechanical properties could be realized via industry viable rolling processing, thus the alloy sheet is highly possible to broaden the applications of Mg alloys in automotive industries. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract A Ca-containing Mg-4Zn-1MM(mischmetal)-0.1Ca (wt.%, ZEX4101) alloy sheet shows Index Erichsen value of 6.7 mm, which is better than commercial Mg alloy sheets. The good formability is attributed to its weakened basal texture, in which the intensity of the (0001) poles of the recrystallized grains spreads towards the transverse direction. By monitoring the microstructural evolution during the hot rolling and the solution treatment, we found that Ca addition hinders the formation of strong basal texture during the rolling. During the subsequent solution treatment, static recrystallization mainly proceeds by the growth of dynamically recrystallized grains, and then the weak texture feature of the dynamically recrystallized grains is maintained in the ZEX4101 alloy sheet. It is hypothesized that co-segregation of Zn and Ca atoms to the grain boundaries prevents the rotation of the (0001) poles of the dynamically recrystallized grains toward the sheet normal direction, resulting in the development of weak basal texture in the ZEX4101 alloy sheet. Highlights • Trace Ca addition weakens basal texture and increases room-temperature stretch formability in Mg-4Zn-1MM alloy sheet. • Ca-containing Mg-4Zn-1MM-0.1Ca alloy sheet causes co-segregation of Zn and Ca atoms to grain boundaries. • Co-segregation of Zn and Ca prevents formation of strong basal texture during hot-rolling. [ABSTRACT FROM AUTHOR]