Papers by Keyword: Deformation Behavior

Abstract: This study investigates the superplastic deformation mechanism of coarse-grain materials .Superplasticity deformation behavior of Ti-22Al-25Nb alloy with 200~410μm coarse grain has been investigated through tensile test at 940~990°C and 3.3× (10^-2~10^-4) s^-1 strain rate. Results prove coarse-grain Ti-22Al-25Nb alloy primary depends on slipping of crystal planes between two phases to achieve superplasticity. Transformation from lath O phase to ring equiaxed O phase occurs as temperature rises and its volume percent falls, but percentage of recrystallized B₂ phase increases. Dislocation can move round ring equiaxed O phase. Good plasticity can be preserved because O phase can flow as solid particle in semisolid slurry in B2 grain.

Abstract: The hot compression deformation behavior of Mg-4Al-1Zn-0.5Mn-0.5Ca (AZ41M) alloys during twin roll casting and hot compression (350-400 oC/0.1-1s^-1) has been studied. Owing to adding Mn and Ca in AZ41 alloy, the deformation behavior and microstructure exhibit largely changes under different conditions. A bimodal structure consisting of a large fraction of deformed grains and a small fraction of newly formed grains are found in as-deformed alloys. Equiaxed and fine-grained microstructures occur in as-annealed samples. Al-Mn and Al-Ca compounds result in grain and Al-Mg intermetallic refinement.

Abstract: The hot compressive deformation behavior of SWRCH 35K was studied with uniaxial hot compression simulation tests at 923 ~ 1223 K and strain rate of 0.01 ~ 20 /s. The results show that the hot compressive deformation activation energy was 408 kJ/mol and the rang of deformation stored energy was 10 ~ 50 J/mol. The quadratic fitting expression between deformation stored energy and Zener-Hollomon parameter (Z) was established and the deformation stored energy was considered to increased with increasing Z or with lower deformation temperature and increasing deformation rate.

Abstract: Magnetic pressure seam welding is a collision welding process, similar to explosive welding, utilizing electromagnetic force as the acceleration mechanism. True metallic bonding is achieved at the mating interface if contact takes place above an appropriate collision point velocity and collision angle. This paper deals with dynamic deformation process on magnetic pressure seam welding of aluminum sheets. Numerical analysis of the dynamic deformation process of the metal sheets is made by a finite element method. In this analysis, the metal sheets (100 mm width, 1 mm thickness) are assumed to be composed of plane-strain quadrilateral elements. The result shows that when the gap length becomes narrow, collision point velocity was decreased early. When the gap length becomes narrow, collision angle was increased slowly.

Abstract: Deposition behavior of Al-Si particles coated on magnesium alloy by Supersonic Particles Deposition (SPD) was investigated by numerical stimulation. The results demonstrated that critical velocity for Al-Si particle to deposit successfully on ZM5 magnesium alloy was about 700m/s; At collision interface, the temperature gradient increased, effective plastic strain change suddenly and stress reduce rapidly to zero. The compression ratio of deposited particles increased. Contacting area at interface enlarged with particle initial velocity increasing. Meanwhile, experimental observation of surface and cross-section morphology of Al-Si coating on magnesium alloy exhibited that, intact particles, fragmented particles and fine particles co-existed in the coating. And the coating was formed by mechanical bonding and metallurgical bonding.

Abstract: The present research is a part of project dealing with structural aspects of ferrite and austenite co-deformation in duplex stainless steels. The examination concerned a development of ferrite and austenite microstructures, major deformation mechanisms operating in both phases and texture formation upon cold-rolling of a model duplex type steel. The investigations showed that the band-like morphology of two-phase structure formed upon processing together with specific starting textures obtained after a preliminary thermo-mechanical treatment exerted significant influence on texture and microstructure development in both constituent phases. Microstructure and texture evolution in examined duplex steel significantly differed from those in one-phase steels. These differences resulted first of all from the role of the phase boundaries acting as the barriers for dislocation movement and affecting the processes of strain localization at higher deformations.

Abstract: Hot compressive deformation of Udimet720Li alloy was carried out on Gleeble-3500 thermal mechanical simulator. The flow stress behavior of Udimet720Li alloy during hot compression was studied in the temperature range of 1100-1160 and at a strain rate of 0.001-1s ^-1. The results showed that the flow stress was controlled by both strain rate and deforming temperature. The flow stress decreased with the increase of deforming temperature, while increased with the increase of strain rate. The change of flow stress with deformation thermal parameters was revealed from true stress-true strain curves, and constitutive relationship of Udimet720Li alloy was obtained on the base of Arrhenius equations and the deformation activation energy was calculated.

Abstract: A series of warm tensile tests for B349/590DP steel are performed at the stain rates of 0.0004/s, 0.001/s, 0.01/s and 0.08/s in this paper. From the test data, it is found that the effect of temperature and strain rate on material’s deformation behaviors is opposite to that of other temperature ranges. And with the change of strain rate and temperature, the relations between the material parameters such as the work-hardening exponent n, the stress hardening coefficient K and forming process conditions becomes uncertain. Moreover, authors investigated the reasons for above phenomena. Research results demonstrate that it is very necessary to appropriately optimize the warm forming process scheme and strictly control the warm forming process parameters so that both the formability and safety performance are considered simultaneously.

Abstract: The present study focused on the influence of the friction coefficient on the deformation behavior in large strain extrusion machining (LSEM). A series of simulation results of effective strain were obtained under different friction coefficients by conducting finite element simulations with a FEM code. The results show that LSEM can produce different effective strains by changing the friction coefficients, thus enabling the fabrication of bulk nanostructured materials. An analysis of the variation of effective strain through the chip demonstrated that the chip deformed much more inhomogeneously when the friction coefficient became larger. The obtained results can offer valuable guidelines for later LSEM studies.

Abstract: Lightweight materials have been in focus in recent times for their use in automobiles, planes and protective structures for numerous benefits ranging from reduction in fuel consumption and increased payload in vehicles to lighter and stronger protective structures. For efficient use of materials in applications where they are subjected to unusual higher sudden loads, it is necessary to understand their mechanical behaviour under such conditions.In present study, the effect of strain rate on deformation of magnesium alloy AZ31Bunder compression has been investigated. The alloy is subjected to various strain rates as 10-4s-1, 500s-1 and 2500s-1 and the microstructural analysis was performed to see the changes in the microstructure of the alloy and their effect on the mechanical response of the alloy is portrayed.