Effects of Impurities and Processing Conditions in Al–1%Mn Alloys on the Formation of Thermally Stabilized Substructures

Abstract

In this study, the effects of impurities and processing conditions on the thermal stability of substructures formed via hot deformation were investigated using a plane strain compression (PSC) test. Two types of Al1%Mn alloys were prepared. One of the alloys had a low content of silicon and iron owing to the use of pure aluminum bare metal (4N1Mn alloy). The other was cast by using A1050 alloy (10501Mn alloy). The PSC tests were performed between 300 and 500°C and were followed by annealing at 500°C for 120 s in a salt bath. After the salt bath treatment, the 4N1Mn alloys exhibited a recrystallized structure, whereas the 10501Mn alloys retained their fiber structure. Although the 4N1Mn alloys exhibited a small increase in conductivity after the PSC test, the conductivity of the 10501Mn alloys showed an apparent increase. The synchrotron radiation analysis confirmed AlMnSi precipitations in the compressed 10501Mn alloys. These precipitations could be the reason for the change in conductivity in the compressed 10501Mn alloys. Precipitations were barely observed for the compressed 4N1Mn alloys, and small precipitations formed during hot deformation seemed to affect the formation of the thermal stabilized substructures. In addition, the study results showed that impurities, such as silicon, contribute to precipitation during hot deformation.

Formation and Dispersion of Precipitates during Hot Deformation in Al–1%Mn Alloys

“…In order to identify precipitates that formed during hot working, X-ray diffraction (XRD) measurements at a wavelength of 0.8692 ¡ were performed on the constriction and invariant areas set at 400°C, as in a previous report. 7) The results are shown in Fig. 9.…”

“…A previous report 7) described how the thermally stabilized substructures formed as the electrical conductivity increased in the constriction areas. The proposed mechanism of the formation of the thermally stabilized substructures is shown in Fig.…”

“…1(a) according to the previous report. 7) The PSC specimens were set to a range between 300 and 500°C, and compressed in thickness from 10 to 5 mm. The strain rate of the anvils was set at 1 s ¹1 .…”

“…The authors prepared specimens in which 1% manganese was added to high purity (99.99% purity, 4N base) ingots and 99.5% purity (1050 alloy base) ingots, and investigated the formation condition on the thermally stabilized substructure by plane strain compression (PSC) test. 6,7) In this test, homogenization treatment was not carried out, because the purpose was to clarify the impact of precipitation behavior which arose during hot compression process. As a result, it was judged that the precipitation was small in the 4N base alloys during the PSC tests because the conductivity changed after the PSC tests.…”