• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.05a
• /
• pp.258-262
• /
• 2008

Micro forming is a suited technology to manufacture very small metallic parts(several $mm{\sim}{\mu}m$). In this study, the micro forming property was studied, using Al5083 superplastic alloy with micro grain, suitable for the micro forming process and Zr-BMG amorphous with pseudo-superplastic phenomena in the supercooled liquid state. Micro forming experiments under stastic load status showed that distortion by slip and spin of the grain system and slip inside the grain was observed in the Al5083 superplastic alloy. In case of Zr-BMG, because there is no grain, the distribution of the forming property was similar to the load distribution between punch and metal.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.4
• /
• pp.876-886
• /
• 1994

Process design in superplastic forming to produce a Nickel-base jet engine disk has been carried out using the rigid-viscoplastic finite element method. This study aims at deriving systematic procedures in forging of superalloy engine disk, and develops a simple scheme to control strainrate within a range of superplastic deformation during the forging operation. The new process, a pancake type preform being used, is designed to have less manufacturing time, and more even distribution of effective strain in the final product, while the conventional superplastic forging of an engine disk has been produced from a cylindrical billet. The jet engine company, Pratt & Whitney, provided the basic information on the manufacturing process of superplastic forging of a jet engine disk.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1998.03a
• /
• pp.65-71
• /
• 1998

The superplastic deformation behaviors of 7075Al alloy have been characterized experimentally and analyzed by the internal variable theory of inelastic deformation. A simple rheological model including the grain boundary sliding has been used to interpret the superplastic deformation behaviors. A series of load relaxation and tensile tests have been carried out for 7075Al alloy at the various temperatures. The superplastic deformation of 7075Al alloy is confirmed to consist of the grain boundary sliding and accommodating grain matrix defprmation.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.9
• /
• pp.778-782
• /
• 2007

In the present study, design and forming process of fabricating titianium lightweight components are developed with applicaton of superplastic forming and diffusion bonding technology. SPF/DB(Superplastic forming/Diffusion bonding) technology is one of the advanced technologies to reduce production cost and weight and currently applied to aircrafts and space launchers in foreign countries. The present study constructs an analysis model to predict superplastic forming behavior of titanium alloy, which is well known for its resistance to deform. The experimental results show the forming of titanium lightweight sandwich structure is successfully performed from 3 sheets of Ti-6Al-4V. The results demonstrate that the developed technology to process design of SPF/DB by the finite element method can be applied to various types of components.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.143-143
• /
• 2003

현대 산업이 발전함에 따라 다양한 기기들의 초소형화가 급속히 진행되고 있다. 이러한 요구에 부응하기 위하여 미세구동소자(Microelectromechanical system)의 개발이 많은 연구 그룹들에 의해서 이루어지고 있다. 미세구동소자에 응용을 하기 위해 개발되어지고 있는 여러 가지 소재들 중 $\ulcorner$형상기억합금 $\lrcorner$은 기존의 바이메탈이나 피에조 소자에 비하여 작동거리가 우수하기 때문에 그 가능성을 인정받고 있지만, 벌크재료는 느린 냉각속도 때문에 반응속도가 느린 단점이 있기 때문에 박막화 할 필요성이 있다. 이러한 이유로 여러 그룹들에 의해 형상기억합금의 박막화가 시도되고 있으나, 조성에 의해 특성의 변화가 심한 형상기억합금의 정밀한 조성제어가 힘들다고 알려져 있다. 몇몇 연구 그룹에서 RF magnetron sputtering법을 이용하여 Ti-Ni합금 박막을 성공적으로 제조하였다는 보고가 있지만, 타겟 조성 및 형태 등의 정밀한 제어가 필요하므로 3원 합금 박막 등을 제조할 경우에는 또 다시 타겟의 조건을 정밀하게 제어해야 할 필요성이 있다. 따라서 본 연구에서는 산화물 박막등의 제조에 있어서 타겟 조성과 제조된 박막 조성이 잘 일치하여 조성제어가 쉽게 이루어진다고 알려져 있는 PLD법을 도입하여 형상기억합금 박막제조에 적용가능한지를 검토하는 것을 목적으로 하였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.10a
• /
• pp.76-79
• /
• 2009

The current understanding for phase/grain boundary sliding and low-temperature/high-strain rate superplasticity of two-phase titanium alloys is summarized. The quantitative analysis on boundary sliding revealed increased sliding resistance on the order of $\alpha/\beta\;\ll\;\alpha/\alpha\;\approx\;\beta/\beta$ boundary, hence, led to the conclusion that approximately 50% alpha(or beta) volume fraction and/or grain refinement is beneficial for obtaining large superplastic elongation at low temperature and/or high strain rate. To predict the temperature for 50% alpha volume in various alpha/beta Ti, artificial neural network was applied. Finally, much enhanced superplasticity was achieved through grain refinement utilizing dynamic globularization.

• Transactions of Materials Processing
• /
• v.21 no.7
• /
• pp.403-411
• /
• 2012

The aim of this study was to predict the results of superplastic forming on magnesium alloy, by considering the grain growth using numerical simulations. Superplastic behavior of AZ31 alloy was investigated through a set of uniaxial tensile tests that cover the forming temperatures ranges from 375 to $450^{\circ}C$. All the material parameters in the model, which consists of a constitutive equation and a grain growth equation, were determined. The model was used in the finite element analysis for uniaxial tensile tests and superplastic blow forming, through a user-subroutine available within ABAQUS. From this study, the effect of grain growth during forming was evaluated. The results show that it is essential to include the effect of grain growth in predicting the behavior during superplastic forming of this magnesium alloy.

• Transactions of Materials Processing
• /
• v.19 no.1
• /
• pp.5-10
• /
• 2010

The current understanding for phase/grain boundary sliding and low-temperature/high-strain rate superplasticity of two-phase titanium alloys is summarized. The quantitative analysis on boundary sliding revealed increased sliding resistance on the order of ${\alpha}/{\beta}\;\ll\;{\alpha}/{\alpha}\;{\approx}\;{\beta}/{\beta}$ boundary, hence, led to the conclusion that approximately 50% alpha(or beta) volume fraction and/or grain refinement is beneficial for obtaining large superplastic elongation at low temperature and/or high strain rate. To predict the temperature for 50% alpha volume in various alpha/beta Ti, artificial neural network was applied. Finally, much enhanced superplasticity was achieved through grain refinement utilizing dynamic globularization.

• Transactions of Materials Processing
• /
• v.11 no.3
• /
• pp.255-261
• /
• 2002

The grain size of 7010 Al alloy was refined to submicrometer level by using equal channel angular pressing (ECAP) and additional warm rolling. The mechanisms of grain refinement in ECAP process were fragmentation of coarse grain to ultra fine subgrains after a few passes and continuous recrystallization of the subgrains with the increase o( passes. Because of ultrafine grain size, essentially low temperature and high strain rate superplasticity was observed after ECAP process and warm rolling to form a sheet metal. The maximum elongation of 700% was obtained for an ECA pressed specimen after IS passes without warm rolling at $450^{\circ}C$ with strain rate of 5x$10^{-3}$/sec.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.129-130
• /
• 1999

The superplastic deformation characteristics is powder metallurgy(PM) Al-Li alloy has been studied within the framework of a recently proposed internal variable theory of superplasticity(SSP). The flow curves were obtained by performing a series of load relaxation tests at the temperature range from 45$0^{\circ}C$ to 52$0^{\circ}C$ It has been found that the overall flow curves were separated into the grain boundary sliding(GBS) and the accommodating dislocation glide processes/ The tensile curves were also obtained to clarify the superplastic deformation bahavior of PM Al-Li alloy. The microstructural features of PM AL-Li alloy have been examined through the transmission electron microscopy.