Deformation and Fracture at High Temperatures in an Al-Mg-Mn Alloy Sheet Consisting of Coarse- and Fine-Grained Layers

Abstract

High temperature deformation and fracture of the Al-Mg-Mn sheet consisting with the coarse-grained surface and the fine-grained center layers have been investigated. Such a microstructure was produced by the continuous cyclic bending (CCB) and the subsequent annealing. The elongation to failure has a peak value at 713 K at initial strain rates of 5.6 × 10 −4 s −1 and 5.6 × 10 −3 s −1 in both of as-received sample (0P) with fine grains and CCBent and annealed one (20P A) with the coarse and the fine grains in spite of different microstructures. The m value decreases for 20P A and increases for 0P with increasing temperature. However, the increase of the m value is not correspondent to the change in the elongation. Deformation mechanism is discussed with activation energy. The SEM micrographs of original surfaces of tensile specimen deformed to failure reveal that at the relatively high temperatures many cracks are formed inside the coarse grains. The features of fractured surface for the 20P A sample reflect the coarse-and the fine-grained layers faithfully.

Change in Crystallographic Orientation Distribution during High Temperature Deformation in an Al-Mg-Mn Alloy Sheet Consisting of Coarse- and Fine-Grained Layers

“…The as-received sheet had been manufactured by the process of casting, homogenizing at 803 K, hot rolling, cold rolling with a reduction of 75% and a final continuous annealing at 673 K. Workpiece with a 500 mm length, a 20 mm width and a 1.5 mm thickness was subjected to CCB in the same way 7) up to 20 passes. From the CCBent workpiece tensile specimens were machined with a 6 mm length, a 4 mm width and a 1.5 mm thickness of the reduced section, and a 6 mm radius of fillets.…”

“…7) Figure 2 displays the inverse pole figure (IPF) maps in tensile direction (RD or L) of the surface coarse-grained layers of the samples deformed up to failure at three strain rates. The IPF map for the sample immediately before testing is also represented.…”

Low-Temperature Superplasticity in an Al–Mg–Mn Alloy Subjected to ECAP and Subsequent Isothermal Rolling

“…This limitation may be overcome by implementation of superplastic forming (SPF) technology of Al-Mg sheets for the fabrication of components with good surface and excellent tolerance [2,3]. However, the utilization of SPF technology in commercial use is currently limited because of the relatively low strain rates and high temperatures associated with superplastic deformation of aluminum alloys with fine-grained structure produced by conventional thermomechanical processing [4,5].…”

Improvement of Fatigue Properties by Means of Continuous Cyclic Bending and Annealing in an Al-Mg-Mn Alloy Sheet

“…12) The sheet consisting of the coarse-grained surface and the fine-grained center layers is supposed to show both advantages in the suppression of the initiation and the resistance of the growth for fatigue crack. The purpose of the present study is to investigate whether the fatigue properties are improved in an Al-Mg-Mn alloy sheet subjected by the continuous cyclic bending and annealing.…”