Aluminium Alloys 2014 - ICAA14

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Authors: Amir M. Horr, Christoph Angermeier, Angela Harrison
Abstract: To achieve a required product quality during Low Pressure Die Casting (LPDC) process, it is necessary to identify and also control the main input parameters affecting the casting defects to arrive at the desired output quality. In industrial scale LPDC, where the issues of part quality, cost, and cast speed are the main driving forces for the industries, the cast process optimization to have minimum defects is quite essential. The LPDC process of light weight metals is defined as a casting process where the die is filled relatively slowly at low pressure. The melt flow regime has low turbulence, and filling process can be defined as relatively smooth filling. In recent years, in order to limit the component defects, the through process simulation has widely been used. In an interactive simulation environment, a full multi-phase casting process simulation (thermal-fluid simulation using multi-physical domain) along with its material and mechanical simulations are carried out in a single environment. One of the main contributions of this paper is to show the advantages of using full through process simulation of LPDC to limit the defect in the component. An experimental program along with a comprehensive process simulation has been setup to optimize the casting process and the results were presented for real world case studies.
Authors: Sergey Komarov, Yasuo Ishiwata, Yoshihiro Takeda
Abstract: The present work introduces a novel ultrasonic DC casting process which allows producing billets of hypereutectic Al-Si alloys with greatly refined and uniformly distributed particles of primary Si. In the process, ultrasonic vibrations are introduced into an Al-17Si-0.01~0.03P melt in a hot top positioned on the mold by using a high-amplitude ceramic sonotrode. The hot top design and sonotrode arrangement provided a highly effective cavitation treatment of the melt in the hot top and well-controlled flow in the sump. A simplified model is proposed to explain the obtained results.
Authors: Jie Hua Li, Mihaela Albu, Thomas Ludwig, Y. Matsubara, Ferdinand Hofer, Lars Arnberg, Y. Tsunekawa, Peter Schumacher
Abstract: The paper provides a new insight into the modification of eutectic Si in Al-Si based alloys. To date, impurity-induced twinning mechanism and twin plane re-entrant edge mechanism are the well-accepted theories. However, neither IIT nor TPRE can be used to interpret all modification observations. Therefore, a re-consideration of modification mechanisms is still required. In this contribution, recent advances on the understanding the modification of eutectic Si are reviewed. Two different cases are highlighted. In the case of Sr, Na and Eu addition, eutectic Si was modified from a faceted to a fibrous morphology, which involves the formation of multiple Si twinning. In the case of Yb and Ca addition, eutectic Si was refined to a smaller size, but still maintained a plate-like morphology. The possible modification mechanism was thus discussed in terms of (i) adsorption of atoms at twin re-entrant edge, and (ii) segregation across {111}Si growth planes. Furthermore, solute entrainment of modifying elements (M) was introduced to interpret the formation of Al2Si2M phase or M-rich clusters within Si crystals.
Authors: Heinrich Möller, Pfarelo Daswa, Gonasagren Govender
Abstract: Limited information is available regarding the heat treatment response of age-hardenable wrought Al-alloys produced by semi-solid metal forming. In this study, the effects of chemical composition, natural pre-ageing and artificial ageing on the T6 properties of rheo-high pressure die cast 6xxx series Al-Mg-Si-(Cu) alloys are investigated. A Cu-free alloy 6082 is compared with Cu-containing alloys 6013 and 6111. The effects of Mg:Si ratio of the alloys are also quantified by means of a comparison between alloys 6111 and 6013. Artificial ageing curves following either no or 5 days of natural pre-ageing are also presented.
Authors: Boris V. Ovsyannikov
Abstract: Recently significant successes have been achieved in the field of grain refinement by means of such additives as the titanium, zirconium, scandium, AlTiB and AlTiC. However, introduction of grain refining additives results to a number of negative effects. These effects can be divided into four basic groups: 1. Reduction of high-strength alloy casting properties. 2. Defects of structure. 3. Intermetallic and oxide inclusions. 4. Decrease in mechanical and fatigue properties of the semis made of ingots with fine grain.
Authors: Jayesh B. Patel, Hu Tian Li, Ming Xu Xia, Simon Jones, Sundaram Kumar, Keyna O'Reilly, Zhong Yun Fan
Abstract: A novel direct chill (DC) casting process, melt conditioned direct chill (MC-DC) casting process, has been developed for production of high quality aluminium alloy billets. In the MC-DC casting process, a high shear device is submerged in the sump of the DC mould to provide intensive melt shearing, which in turn, disperses potential nucleating particles, creates a macroscopic melt flow to uniformly distribute the dispersed particles, and maintains a uniform temperature and chemical composition throughout the melt in the sump. Experimental results have demonstrated that, the MC-DC casting process can produce aluminium alloy billets with significantly refined microstructure and reduced cast defects. In this paper, we give an overview of the MC-DC casting process and report on results obtained from an industrial scale trial.
Authors: Vadakke Madam Sreekumar, Nadendla Hari Babu, Dmitry G. Eskin, Zhong Yun Fan
Abstract: In this study, grain refinement efficiency of a new oxide master alloy based on MgAl2O4 was demonstrated on an A357 alloy. The grain size of the reference alloy was reduced by 50-60% with the addition of the master alloy and introduction of ultrasonic cavitation. A higher addition of master alloy was found to be not benificial in further reducing the grain size.
Authors: Mark A. Easton, Arvind Prasad, David H. St. John
Abstract: Recent work has extended the Interdependence Model to the prediction of grain size of aluminium alloys when refined by Al-Ti-B master alloys. The relative contribution of Ti solute and TiB2 particles to the as-cast grain size was determined indicating the optimum level of addition required to provide cost effective use of master alloy. This paper quantifies the effect of Al5Ti1B master alloy additions on the grain size of Al-Si alloys. The Al-Si system is a special case where additions of Si above a few percent poison grain refinement resulting in larger grain sizes. Consideration of the complicating effect of Si poisoning on the prediction of the grain size of these alloys and possible approaches to dealing with these complications are presented.
Authors: Xiang Jie Wang, Gang Sun, Li Juan Wang, Peng Wei Li, Jian Zhong Cui
Abstract: Aluminum is the richest metallic element in the earth, the ingots cast by DC casting process are usually extruded into aluminum bars. When the final products do not require high strength, this process appears to be low efficiency and high cost. We try to design a new technology to cast aluminum bar by horizontal direct chill (HDC) casting process directly. An electromagnetic field is applied during the horizontal continuous casting of 6061 aluminium bar with a diameter of 30mm. The experimental results show the asymmetry of the sump can be overcome by electromagnetic field. Ingot with good upper and lower surface quality is obtained. The structure of ingot is refined and the angle between growth direction and horizontal direction becomes small with increasing casting speed.
Authors: Feng Yan, Shou Xun Ji, Zhong Yun Fan
Abstract: This paper presents the effect of Cu on the microstructure and mechanical properties of diecast Al-8Mg2Si-6Mg-0.6Mn alloy. The Cu addition in the Al-8Mg2Si-6Mg-0.6Mn alloy can slightly increase the yield strength but decrease the elongation and ultimate tensile strength. Consequently, Cu is considered as a detrimental element in the alloy.

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