International Research Journal of Engineering and Technology (IRJET) Volume: 09 Issue: 06 | Jun 2022
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e-ISSN: 2395-0056 p-ISSN: 2395-0072
Refinement and redistribution of intermetallic compounds in AA 7xxx alloyby rolling and their effect on formability studies K. SAI PRASAD1, R. MOHANA RAO2, V. GANESH3, A. PARAMESH4, V.V.RAVI KUMAR5 1Associate
Professor, Department of Mechanical Engineering, Nadimpalli Satyanarayana Raju Institute of Technology, Visakhapatnam, Andhra Pradesh, India 2,3,4,5 Student, Mechanical Engineering, Nadimpalli Satyanarayana Raju Institute of Technology, Visakhapatnam, Andhra Pradesh, India ---------------------------------------------------------------------***--------------------------------------------------------------------Abstract- Thermo-mechanical treatment, in compared to SPD method at ambient temperature [6]. The
tensile strength was decreased while the elongation was improved gradually with increasing annealing temperature [7]. Low-temperature aging treatment on cryo-rolled Al 7075 and Al 2024 alloy was carried out by Zhao et al.(2005) and Cheng et al.(2007), who obtained huge improvement of [8-9]. Formability of the material is the capability of the material to undergo plastic deformation to a given shape, without defects. Forming limit diagrams (FLD) were used for the prediction of deformation factors that could result in the failure of the material under different strain ratio. FLDs proposed as an important tool in the forming behavior of sheet metals and in the optimization of manufacturing industries as reported by Kleiner et al. (2008) [10]. Kirstensson et al. (2006) reported a numerical study of micro- mechanical modeling affecting the formability [11]. To evaluate the ductile fracture of Al alloy sheets was Ultra-fine proposed by Daoming Li, et al. (2004) and predict the forming limit of Al alloys, proved an effective tool [12].
particular, cold-rolling is a unique technique to produce super high strength aluminum alloys with ultrafine grained structure. In the present study, 7xxx series aluminum alloy with high alloying additions (Zn: 12%, Mg: 3% Cu: 2%, and 0.5% SC wt.) was rolled at different temperatures (Room temperature). Since the alloy consists of segregated compounds along the boundaries, non-isothermal step rolling was carried out to condition the alloy and followed by rolling. Optical microscopy, SEM, hardness and tensile testing were conducted on the rolled alloy for understanding the phase changes and evaluating the mechanical properties. It is noticed that the ductility of the rolled alloy is getting restored with desirable strength by short annealing. The formability of the rolled sheets of all conditions was investigated. Keywords:
Aluminium alloys, Rolling, Structure, Formability.
1. Introduction
2. Experimental Procedure
A material possessing desirable properties is the recent requirement in engineering applications. Light weight, formability and strength are the most important properties opted by the designer in the selection of a material for most of the advanced engineering applications. In specific, AA7xxx series alloys are widely used in aerospace applications due to their good specific strength, formability, resistance to various corrosive media, etc. [1-3], either soluble or insoluble in nature. It was proved that cryo rolling of aluminum alloys had resulted in ultrafine grains (UFG) with sufficient ductility. The cold rolling process cannot be used to produce UFG structure in AA7xxx alloys due to its high strength, poor ductility and high stacking fault energy. When the forming operation was carried out at room temperature, the quality of the surface of a final product was poor. It had been reported that the surface quality and improved ductility in high strength alloy could be obtained by conducting forming operation in the temperature range from 100 to 450˚C [4-5]. Cryo-rolling has been established as one of the leading routes to produce nano-crystalline (NC) / UFG pure metals Cu, Al, Ni from its bulk counterparts by deforming them at cryogenic temperature. Wang et al. (2002) produced UFG structure of commercial pure Cu by cryo-rolling at the lower temperature
Al–12Zn–3Mg–2.5Cu-0.5%SC (wt. %) alloy billet was prepared by controlled process parameters. A sample coupon for rolling at appropriate temperature was cut from the billet. The sample size of 35mm × 35mm × 6mm was used for non-isothermal rolling and followed by cold rolling. The alloys were multi-pass rolled from 6 mm to reduction in thickness 1mm. Cold rolled alloy were subjected to short annealing at 200°C for 10 min. The sample size of 30mm×30mm×1mm was used for conduct of formability studies. Chemical etching method printed by the grid patterns. The circle diameter of the grid was 2.5 mm. Forming up to fracture was carried out on a double action hydraulic press of capacity 2000 kN using standard die and punch set up. Figure 1 depicts the photograph of the formability testing machine and sample used for test. The major diameter, minor diameter values, the major strains (ε1) and the minor strains (ε2) were calculated using the following empirical equations.
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Major strain (ε 1) = ((major diameter – 2.5 mm) / 2.5mm) x 100 -------1 Minor strain (ε 2) = ((minor diameter – 2.5 mm) / 2.5mm) x 100 -------- 2
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