The Effect of Deformation Ratio and Heat Treatment Time on the Microstructure and Mechanical Properties of A356 Aluminium Alloy During SIMA Process
Mahdi Amne Elahi,
Hossein Gheisari,
Saeed Shabestari
Issue:
Volume 2, Issue 3, May 2017
Pages:
28-33
Received:
30 May 2017
Accepted:
4 July 2017
Published:
27 July 2017
Abstract: The influence of Strain Induced Melt Activated (SIMA) parameters on the globularization of α-Al and microstructure in A356 aluminium alloy were investigated in the present study. After production of samples using conventional permanent mold casting and cold rolling at various reduction, they were heat treated at 590°C for different holding time to spherodize the microstructure. The results indicated that, the grains became smaller, more spherical and having a homogenous distribution by increasing the deformation ratio. Increasing the holding time in heat treatment results the growth of globular grains. The necessary strain for recrystallization is about 15% and the optimum condition was achieved in the samples were 15% rolled and heat treated for 15 minutes at semi-solid temperature, regarding the maximum shape factor and minimum globular grains size. Further increasing in holding time is responsible for grain growth and hardness decline.
Abstract: The influence of Strain Induced Melt Activated (SIMA) parameters on the globularization of α-Al and microstructure in A356 aluminium alloy were investigated in the present study. After production of samples using conventional permanent mold casting and cold rolling at various reduction, they were heat treated at 590°C for different holding time to ...
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Effective Technological Process of Crystallization of Turning Rollers' Massive Castings: Development and Analysis
Tamara Skoblo,
Oksana Klochko,
Efim Belkin,
Aleksandr Sidashenko
Issue:
Volume 2, Issue 3, May 2017
Pages:
34-39
Received:
20 June 2017
Accepted:
12 July 2017
Published:
27 July 2017
Abstract: The paper describes a new method of maximum reducing residual stresses and stabilization of the structure, hardness of the working layer of massive sheet rolls from alloyed cast irons during their crystallization due to controlled decomposition of retained austenite. It is achieved by programmable preheating of the metal form to the temperature of magnetic transformation of doped cementite or special carbides of the castings (depending on the material being processed); meanwhile it is provided an optimum cooling rate with an exposure of up to 6 hours in this interval and maximizes decomposition of retained austenite, minimizes stresses in the working layer. This casting technology is also accompanied by appropriate structural changes. Inhomogeneity of the dislocation structure is noted in various constituent phases. Polygonization and fragmentation along dislocation walls are revealed in the carbide phase. To evaluate the occurring processes, a new method of optical and mathematical description of the phases being formed is used. As a criterion describing the changes in the dislocation structure, we use the parameter - a power dissipation power function. The proposed casting technology for rolls is particularly effective when the proportion of the carbide phase is at least 25%. In this case, the heat treatment of the rolls to relieve stress does not change the stably achieved properties. It is shown that the quality control on the stability of the achieved indicators can be carried out by the coercive force and the level of hardness.
Abstract: The paper describes a new method of maximum reducing residual stresses and stabilization of the structure, hardness of the working layer of massive sheet rolls from alloyed cast irons during their crystallization due to controlled decomposition of retained austenite. It is achieved by programmable preheating of the metal form to the temperature of ...
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