Papers by Keyword: Pre-Deformation

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Authors: Michal Kolar, Katharina Teichmann, Sverre Gulbrandsen-Dahl, Ketill Olav Pedersen, Knut Marthinsen
Abstract: In the present work we report on the effect of pre-deformation followed by/together with artificial aging on the mechanical properties as strength, ductility and work hardening of an Al-Mg-Si alloy (AA6060). The AA6060 alloy was initially cast, homogenized and extruded according to standard industrial practice. The extruded material was then subjected to a solution heat treatment and subsequently artificially aged after (sequential mode) and during (simultaneous mode) various combinations of deformation (0-10%) and heat treatments. The aging behaviour and mechanical properties have been characterized in terms of Vickers hardness and tensile testing. It is found that small, even very small, pre-deformations strongly affect the aging behaviour and associated tensile properties. Moreover, it is found, that with the carefully chosen parameters of simultaneous deformation and aging one can reach mechanical properties superior to those following pre-deformation and subsequent aging (sequential mode). The results are compared and discussed in view of differences in processing conditions and microstructure characteristics.
Authors: Shi Chun Zhu, Xiao Feng Lu, Jian Ming Gong
Abstract: In this paper, effect of pre-deformation and ageing on compressive behavior of Ti-58.25wt%Ni was investigated at room temperature. Through range analysis of three factors and three levels on transformation temperature measured by DSC, ageing at 673K enhanced phase transformation temperature obviously, the As temperature could reach 308.02K. Transformations of B2-B19’ and B2-R-B19’ appeared after the treatments. Saw tooth shape phenomenon on the loading curves indicating the typical martensitic transformation was also observed. Dynamic balance due to compatible action among various phase under increased load kept the slope of the loading curves constantly. Pre-deformation by 0.2% resulted in higher compressibility (4.9%), and ageing at 523K caused better recovery (95.4%).
Authors: Jia Wang, De Hong Lu, Han Xiao, Rong Feng Zhou, Rong Zhou, Long Biao Wu
Abstract: Semi-solid billet of ZCuSn10 (Wt%: 88.25Cu, 10.48Sn) alloy is prepared by strain induced melt activated (SIMA) method which including rolling and remelting process. Firstly, ZCuSn10 alloy is casted, and rolling samples are cut from ingot casting. Secondly, the rolling samples are two pass or four pass rolled after holding 15 minutes at 450°C, then samples with 10% and 20% pre-deformation degree are obtained. The remelting samples are cut from pre-deformed samples. Lastly, the remelting samples are reheated up to 850°C or 875°C, water quenching after holding for 15 minutes. Then semi-solid microstructure of ZCuSn10 alloy is prepared. The semi-solid microstructure of ZCuSn10 alloy is observed and compared with annealed microstructure and microstructure of ZCuSn10 alloy directly remelted after casting. The results indicate that semi-solid microstructure of ZCuSn10 alloy by rolling-remelting SIMA process is uniform and fine grain, and spheroidization level of solid particle is well. The optimum semi-solid microstructure is obtained when alloy with pre-deformation 20% is remelted at 875°C for 15 minutes, the average grain diameter is about 75.80μm, shape factor is 1.62, and volume fraction of liquid phase reaches about 17.28%. Pre-deformation process plays a crucial role in grain refinement and spheroidization during SIMA process for preparing the semi-solid ZCuSn10 alloy, as pre-deformation degree and remelting temperature increases, volume fraction of liquid phase increases, the solid particles in semi-solid microstructure are smaller and rounder. The main mechanism of SIMA process preparing semi-solid billet of ZCuSn10 alloy is that pre-deformation breaks dendrites and stores energy of deformation into alloy, and promotes dendrites fusing through remelting process. Meanwhile, liquid phase occupies sharp corners of solid particles by Sn element diffusing from liquid phase into α solid phase, so that fine and uniform and globular α solid particles are gained.
Authors: Yu Zhang, Fu Shun Liu
Abstract: Effects of mechanical treatment, pre-strain and pre-deformation temperature on shape recovery stress of Ti50Ni47Fe3 shape memory alloys were investigated. Mechanical treatment, consisting of hot-rolling and hot-forging, improved σrmax σrmax (maximum recovery stress), dσr/dT (rate of recovery stress with temperature) and Ts (the temperature at which recovery stress rises sharply). Martensitic transformation and reverse transformation temperatures also increased with increasing the hot-rolling deformation. σrmax and dσr/dT increased with increasing pre-strain at first and then decreased with further increasing of pre-strain, and the maximum values of σrmaxand dσr/dT were obtained at a pre-strain of 10%. On the other hand, σrmaxand dσr/dT decreased with increasing pre-deformation temperature. Upon a hot-rolling of 88% area reduction and pre-deformation of 10% at-150°C, the Ti50Ni47Fe3 alloy exhibited excellent recovery stress property with the σrmax of 391MPa in combination with dσr/dT of 5.09.
Authors: Kiyomichi Nakai, Norihiro Kanno, Ryo Asakura, Tatsuaki Sakamoto, Sengo Kobayashi, Masahiko Hamada, Yuichi Komizo
Abstract: Intragranular bainite is known to be effective to develop toughness greatly in steels. Effects of aging below eutectoid temperature before austenitization, the deformation before solution treatment and the duration of solution treatment on nucleation of intragranular bainite have been examined. In the austenite (γ) region where carbide pre-existed, the stress due to inverse transformation, ferrite (α) to γ, would be introduced into fine austenitized region with lower transus temperature to γ, resulting in the introduction of stable small-angle boundary at high temperatures acting as the nucleation site for intragranular bainite lath. Deformation of α by cold rolling before solution treatment enhances the nucleation of intragranular bainite, suggesting that the above γ region through the inverse transformation is easily deformed by the hardened neighboring α. In the deformed γ region, small-angle boundary would be more easily introduced, acting as nucleation site for intragranular bainite. Intragranular bainite lath grew and hardness decreased by prolonging the duration of solution treatment, indicating that transformation stress introduced by the pre-treatment was influenced by solution treatment. The effect of sulfur addition on formation of intragranular bainite was also analyzed.
Authors: Jun Ying Min, Jian Ping Lin, Li Jiu Xin, Jia Yue Li
Abstract: During the indirect hot stamping process of boron steel, the pre-deformed component undergoes air cooling, one-side-contact cooling and both-side-contact cooling phases successively. The effects of pre-deformation and cooling rate on the phase transformation should be understood before conducting indirect hot stamping experiments of vehicle components. Uniaxial tensile tests of boron steel at RT were carried out to obtain specimens with different pre-strain levels. Then they were heated to 900°C according to the indirect hot stamping process and quenching tests were performed on them at different cooling rates. Metallographic observations were performed on the quenched specimens and their hardness was measured. The results show that the pre-strain at RT has little influence on the phase transformation of boron steel. This is due to the dislocation structure introduced by deformation at RT recovered during the heating process and it is good for the indirect hot stamping. Upper B-pillar parts were first cold pre-formed, and then were heated and hot stamped. The microstructure and hardness results at different locations on the indirect hot stamped components are demonstrated qualified.
Authors: Rafael Ferragut, Alberto Somoza, Alfredo Tolley
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