Evolution of the Cracks, Microstructure, and Properties of AA7020 Twin-Roll Casting Sheets during Warm Rolling Processes

In this study, a twin-roll casting sheet of 6061 aluminum alloy was cooled using furnace, asbestos, air, wind and water. The effect of cooling rate on the microstructure and properties of twin-roll casting 6061 aluminum alloy sheet were studied. Optical microscope, scanning electron microscope, X-ray diffraction, microhardness tester and universal tensile machine were used to observe the microstructure and properties of twin-roll casting sheet of 6061 aluminum alloy. The results show that the higher the cooling rate, the smaller the grain size of the alloy and the smaller the number of precipitated phases in the matrix. Uniform grain size of the alloy could be obtained at a stable cooling rate. The hardness, tensile strength and elongation of the twin-roll casting sheet increased with cooling rate. Under wind cooling condition, the twin-roll casting sheet demonstrated excellent comprehensive performance, i.e., 88 MPa of yield strength, 178 MPa of tensile strength and 15% of elongation, respectively. A quantitative Hall–Petch relation was established to predict the yield strength of 6061 twin-roll casting sheets with different grain sizes and cooling rate.

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Three-Ply Al/Mg/Al Clad Sheets Fabricated by Twin-Roll Casting and Post-treatments (Homogenization, Warm Rolling, and Annealing)

Metallurgical and Materials Transactions A ◽

10.1007/s11661-016-3842-7 ◽

2016 ◽

Vol 48 (1) ◽

pp. 57-62 ◽

Cited By ~ 5

Author(s):

Jaeyeong Park ◽

Hyejin Song ◽

Jung-Su Kim ◽

Seok Su Sohn ◽

Sunghak Lee

Keyword(s):

Warm Rolling ◽

Twin Roll Casting ◽

Roll Casting ◽

Twin Roll

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Aging Effect on Texture Evolution during Warm Rolling of ZK60 Alloys Fabricated by Twin-Roll Casting

Metallurgical and Materials Transactions A ◽

10.1007/s11661-010-0336-x ◽

2010 ◽

Vol 41 (10) ◽

pp. 2575-2583 ◽

Cited By ~ 17

Author(s):

Jae-Hyung Cho ◽

Hong-Mei Chen ◽

Shi-Hoon Choi ◽

Hyoung-Wook Kim ◽

Suk-Bong Kang

Keyword(s):

Texture Evolution ◽

Aging Effect ◽

Warm Rolling ◽

Twin Roll Casting ◽

Roll Casting ◽

Twin Roll

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Effect of Thermomechanical Processes on Twin Roll Casted Magnesium Alloy Sheets

Materials Science Forum ◽

10.4028/www.scientific.net/msf.783-786.369 ◽

2014 ◽

Vol 783-786 ◽

pp. 369-374

Author(s):

Ozgur Duygulu ◽

Selda Ucuncuoglu ◽

Gizem Oktay Secgin

Keyword(s):

Electron Microscopy ◽

Magnesium Alloy ◽

Tensile Tests ◽

Warm Rolling ◽

Age Hardening ◽

Forming Limit ◽

Casting Technique ◽

Twin Roll Casting ◽

Roll Casting ◽

Twin Roll

6 mm thick and 1500 mm wide magnesium alloy AZ31, AZ61, AZ91, AM50 and AM60 sheets were produced by twin roll casting technique. Sheets were homogenized between 350-475oC for 1-24 h. AZ31 sheets were rolled down to 1 mm by symmetrical warm rolling and asymmetric warm rolling. Age hardening was also performed on magnesium alloy AZ91 sheets. Specimens were aged at 100-300oC for up to 100 h. Characterization was performed by light microscope, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), transmission electron microscopy (TEM) and x-ray diffraction (XRD) after twin roll casting and also after each thermomechanical process including aging. Tensile tests and micro hardness tests were performed for mechanical properties. In addition to the room temperature tests, elevated temperature tensile tests were also performed at 100, 150, 200, 250, and 300oC at various deformation speeds. Forming limit diagram of the material was determined under warm forming condition.

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The Development of Superplastic Magnesium Alloy Sheet

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.433.273 ◽

2010 ◽

Vol 433 ◽

pp. 273-279 ◽

Cited By ~ 4

Author(s):

Richard J. Dashwood ◽

David Klaumunzer ◽

Martin Jackson ◽

Zhong Yun Fan ◽

Roger Grimes

Keyword(s):

Magnesium Alloy ◽

Magnesium Alloys ◽

Warm Rolling ◽

Alloy Sheet ◽

Magnesium Alloy Sheet ◽

Twin Roll Casting ◽

Roll Casting ◽

Strip Cast ◽

Twin Roll ◽

Cast Condition

While magnesium alloys are routinely used in engineering applications in the form of net shape castings, applications for sheet product have been limited due to the poor cold formability of magnesium combined with the perceived expense of sheet. The issues associated with poor cold formability could largely be overcome if magnesium alloys were to be superplastically formed. Superplasticity in magnesium is well established with research papers on the subject dating back to the late 1960s. In recent years, interest in this area has grown to the point where a number of companies have successfully superplastically formed prototype automotive panels from magnesium alloy sheet. Concurrent to this the scientific community have demonstrated superplasticity in a wide range of magnesium alloys using processing techniques ranging from the exotic (severe plastic deformation) to the mundane (traditional warm rolling). Work by the current authors has shown, rather surprisingly, that superplasticity can be achieved in magnesium alloys in the as-cast condition. This has led to some initial exploratory work involving twin roll casting. The concept being that affordable superplastic magnesium sheet could be produced via twin roll casting with only limited rolling reduction to final gauge. This paper describes the superplastic behaviour (in uniaxial tension) and microstructure of sheet processed from strip cast AZ31 and AZ91. The experimental material has included strip cast AZ91 subjected to large shear strains immediately prior to casting. The material was tested in the as-cast condition and after warm rolling to a number of gauges. Industrially useful superplastic capability was demonstrated in the strip cast alloys. Furthermore, good superplastic capability was also demonstrated in sheet subsequently rolled from the cast metal and rolling strain did not significantly influence the ductilities obtained. The mechanism for achieving superplasticity in as-cast magnesium alloys will be considered and the contrasting deformation characteristics of AZ31 and AZ91 will be discussed in terms of m value analysis and microstructural characterisation.

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