EFFECT OF CUBE TEXTURE ON THE PLANAR ANISOTROPY IN A NOVEL Al-Mg-Si-Zn ALLOY *Zhenshan Liu 1,2,a , Pizhi Zhao 1,2,b , Yiheng Cao 1,2,c and Jingwei Zhao 1,2,c 1 Chinalco Material Applications Research Institute Co.LTD Future Science and Technology Park, Changing District, 102209 Beijing China (*Corresponding author:[email protected]) 2 Chinalco Research Institute of Science and Technology Future Science and Technology Park, Changing District, 102209 Beijing China ABSTRACT A new Al-Mg-Si-Zn alloy designed for automotive outer panel was trial-produced with industrial procedure. The final product shows a strong planar anisotropy. X ray diffraction analysis shows such strong anisotropy is caused by the dominating cube texture component in the final product. The reason for such high cube texture component was investigated by tracing texture evolution starting from the hot roll slab. It is found that certain cube texture components already exists in the hot rolled slab. The density of cube texture component shows as a wavy change through the following 1 st cold rolling, inter-annealing, 2 nd cold rolling and solution treatment. This study shows that the cold rolling in the laboratory can well represent the texture evolution during the industrial production. The results obtained by lab rolling hints that change of second cold rolling reduction has weak effect on the planar anisotropy, when the gauge of hot rolled slab and final sheet are fixed. KEYWORDS Aluminum alloys, Texture, Anisotropy, Annealing, Rolling reduction Published in the Proceedings of the 16th International Aluminum Alloys Conference (ICAA16) 2018 ISBN: 978-1-926872-41-4 by the Canadian Institute of Mining, Metallurgy & Petroleum
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EFFECT OF CUBE TEXTURE ON THE PLANAR ANISOTROPY IN A NOVEL Al-Mg-Si-Zn
ALLOY
*Zhenshan Liu1,2,a, Pizhi Zhao1,2,b , Yiheng Cao1,2,c and Jingwei Zhao1,2,c
1 Chinalco Material Applications Research Institute Co.LTD
Future Science and Technology Park, Changing District, 102209 Beijing China
2 Chinalco Research Institute of Science and Technology
Future Science and Technology Park, Changing District, 102209 Beijing China
ABSTRACT
A new Al-Mg-Si-Zn alloy designed for automotive outer panel was trial-produced with industrial
procedure. The final product shows a strong planar anisotropy. X ray diffraction analysis shows such strong
anisotropy is caused by the dominating cube texture component in the final product. The reason for such
high cube texture component was investigated by tracing texture evolution starting from the hot roll slab. It
is found that certain cube texture components already exists in the hot rolled slab. The density of cube
texture component shows as a wavy change through the following 1st cold rolling, inter-annealing, 2nd cold
rolling and solution treatment. This study shows that the cold rolling in the laboratory can well represent
the texture evolution during the industrial production. The results obtained by lab rolling hints that change
of second cold rolling reduction has weak effect on the planar anisotropy, when the gauge of hot rolled slab
and final sheet are fixed.
KEYWORDS
Aluminum alloys, Texture, Anisotropy, Annealing, Rolling reduction
Published in the Proceedings of the 16th International Aluminum Alloys Conference (ICAA16) 2018 ISBN: 978-1-926872-41-4 by the Canadian Institute of Mining, Metallurgy & Petroleum
INTRODUCTION
With the rapid progress of light-weighting in the automotive industry, aluminum sheets get more
and more application as closure panel and structure parts. Recently the dominating alloy for outer panel is
6xxx series, containing the main alloy elements Mg and Si. The popular grades are AA6016, AA6111,
AA6022, and AA6014. These alloys still cannot satisfy the various requirements from automotive
manufacturers. Most suppliers of automotive aluminum sheets are developing their own specific grades
according to the customer’s demand. To increase the baking response, a new Al-Mg-Si-Zn alloy was
designed, concerning the high combination energy between Zn solutes and vacancies formed during the
quenching stage of automotive sheet manufacture. This combination is helpful to the precipitation of β”
phase during the paint baking (Wang, 2015, 2016; Yan, 2014).
The plastic strain ratio (r value) is a key index of the formability of automotive body sheet. A high
r value means a good formability. The r values in different directions can be used to evaluate the planar
anisotropy of the metal sheets. The trial produced Al-Mg-Si-Zn sheet shows a strong planar anisotropy with
respect to r values. Since the r value is tightly related with texture, the texture evolution from hot roll slab
(HRS) to final T4P temper was analyzed with X ray diffraction (XRD) to find the reason for the high
anisotropy. Besides, the cold rolling reduction (CRR) was varied in the laboratory to modify the texture
distribution, i.e., the planar anisotropy.
EXPERIMENTAL
The investigated Al-Mg-Si-Zn sheet was produced by Southwest Aluminum (Group) Co., Ltd. The
chemical composition range is given in Table 1. The HRS was cold rolled from 5.7 mm to 3.2 mm firstly.
The 1st cold rolled sheet is denoted as CR1. Then it was inter-annealed at the temperature of 420℃ for 2
hours, denoted as AIA. With the 2nd cold rolling the gauge reached 0.98 mm, i.e., 2nd CRR is 70%. This
sheet is denoted as CR2. After following solution treatment at the temperature of 545℃ with continuous annealing line, the sheet was water quenched. The consequent T4P was given by pre-aging. For
convenience to refer, the sheet fabricated in plant is named as “plant 70%”.
Table 1. Chemical composition range of investigated alloys (mass, %)