Saeed Tamimi

Accumulative Roll Bonding of Pure Copper and IF Steel

Severe plastic deformation is a new method to produce ultrafine grain materials with enhanced mechanical properties. The main objective of this work is to investigate whether accumulative roll bonding (ARB) is an effective grain refinement technique for two engineering materials of pure copper and interstitial free (IF) steel strips. Additionally, the influence of severely plastic deformation imposed by ARB on the mechanical properties of these materials with different crystallographic structure is taken into account. For this purpose, a number of ARB processes were performed at elevated temperature on the materials with 50% of plastic deformation in each rolling pass. Hardness of the samples was measured using microhardness tests. It was found that both the ultimate grain size achieved, and the degree of bonding depend on the number of rolling passes and the total plastic deformation. The rolling process was stopped in the 4th cycle for copper and the 10th cycle for IF steel, until cracking of the edges became pronounced. The effects of process temperature and wire-brushing as significant parameters in ARB process on the mechanical behaviour of the samples were evaluated.

Microstructure and mechanical properties of Al-1050 during incremental ECAP

Incremental ECAP is a new method of ECAP process were the severe shear deformation is incrementally applied on the sample resulting in grain refining and new texture developing. The fundamental objective of the present work is an observation of effect of different passes of I-ECAP on microstructure and mechanical properties of AA1050 billet. To that end, 8 pass of I-ECAP have been carried out using Bc route and microstructure evolution and mechanical properties of the I-ECAPed samples have been studied. The EBSD and TEM analyses indicates that I-ECAP is as capable as conventional ECAP to grain refinements and a UFG structure is resulted after I-ECAP cycles. Tensile testing and hardness measurements indicates that mechanical properties of the Al-1050 billets increases dramatically by increasing the I-ECAP passes.

Research directions in hydroforming technology

This paper both summarizes and explores the literature published between 1995 and 2015 on enhancing and extending hydroforming technology. M any different research areas have been proposed, all of which try to enhance the well-established manufacturing process by either improving formability or reducing costs. Each of the technological variations are first described and then their uses, benefits, drawbacks, and applications are discussed and summarized.

Effect of channel angle on the material flow, hardness distribution and process forces during incremental ECAP of Al-1050 billets

Incremental equal channel angular pressing (I-ECAP) is an extension of the classical ECAP method used to produce ultrafine grained (UFG) metals. This paper investigates the first pass of I-ECAP performed on AA-1050 billets measuring 10x10x60mm and the effects of processing with two different dies with the channel intersection angle ϕ=90° and ϕ=120°. The forces required to produce billets were examined and compared. Micro hardness measurements were performed to create a hardness distribution contour map and to evaluate the strain distribution. Moreover FE simulations were performed to investigate the plastic strain distribution within the billets. It was found that using the ϕ=90° die results in higher deformation forces and also greater uniformity of strain distribution when compared to billets processed with ϕ=120° die. The experimental results correlated well with the findings of the simulations.

Modelling the Portevin-Le Chatelier effects in aluminium alloys

Abstract Plastic deformation processes are among the most demanding processes in manufacturing because they lead to different microstructure features in the materials produced. Various dislocation patterns can be induced by plastic strain under different conditions. A serrated yielding/jerky flow in some dilute alloys, such as aluminium-magnesium alloys during plastic deformation, is a well-known phenomenon under certain regimes of strain rate and temperature, as reported in a significant number of works. The serrated features in these materials reflect the so-called Portevin-Le Chatelier effects. These undesirable effects are due to the interaction between solute atoms and mobile dislocation during the plastic deformation, which is known as dynamic strain ageing. There are a significant number of theoretical and numerical investigations that have focused on describing the serrated behaviours of these materials during plastic deformation. Hence, the fundamental objective of this paper is to provide a general review of different constitutive modelling in regards this feature. The typical material models and new constitutive models describing this feature are presented. In addition, applications of the models are provided along with their respective advantages and disadvantages.

THE EFFECTS OF ACCUMULATIVE ROLL BONDING PROCESS ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF IF STEEL

This work aims to investigate whether accumulative roll bonding (ARB) is an effective grain refinement technique for ultra-low-carbon steel strips containing 0.004% C. For this purpose, a number of ARB processes were performed at 500 °C, with 50% reduction in area of each rolling pass. It was found that both the ultimate grain size achieved, as well as the degree of bonding, depend on number of rolling pass and reduction of area as a whole. The mean grain size was obtained using AFM was about 130nm. The mechanical properties after rolling and cooling were obtained. Also, the fracture surfaces were studied by Scanning Electron Microscopy (SEM). It was concluded that metals tensile strengths increased by 334% while the ductility dropped from a prerolled value of 50.5% to 2.6%. Effect of wire brushing on samples observed too. It increased on the wire brushed sheet for 7 HV. The rolling process was stopped when cracking of the edges became pronounced.