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Ageing Process and Mechanical Properties of Hot Extruded Steel Aermet100

Author: TangLiNa
Tutor: ZuoMuFu
School: Harbin Institute of Technology
Course: Materials Science
Keywords: steel AerMet100 hot extrusion ageing process processing optimization
CLC: TG156.92
Type: Master's thesis
Year: 2008
Downloads: 38
Quote: 1
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Abstract


This paper deals with the ageing treatments, microstructure and mechanical properties of hot extruded steel AerMet100. The temperature, stress and strain fields of hot extruded deformation process of steel AerMet100 are simulated by DEFORM software. The optimized ageing parameters have been obtained based on a series of experiments on the hot extruded steel AerMet100. BP artificial neural network (BPANN) models are to characterize tensile strength and toughness as a function of aging temperature and time, and optimize ageing treatment. The optimum ageing parameters have been predicted using the models mentioned above and proved by experimental test.The results from DEFORM simulation for the hot extrusion of steel AerMet100 show that the mesh distortion aggravates with a development of the hot extrusion deformation, and the distortion near the working space of female die where is bigger deformation zone is severest. During deforming, temperature at the center of sample is higher than that of other zones, temperature of the upper outside of sample is lower resulting from the heat conduction, and the highest temperature occurs at the working space of female die. In addition, the equivalent stress and strain also have larger values near the working space of female die. And the equivalent ones of outside surface are larger than those at the sample center.Ageing treatments for hot extruded steel AerMet100 are investigated in the temperature range of 425~510oC. The results demonstrate that the HRC peak value is HRC 55.62 when the ageing is conducted at 460oC for 7 h. Moreover, as the temperature rises and holding time prolongs, the ultimate tensile strength reduces and toughness increases resulting from the tensile and impact test results under different aging treatments. The optimum ageing processing is 460?C×7h under this experimental condition.The mathematical models for characterizing the effects of ageing treatment parameters on ultimate tensile strength and impact energy are developed based on three-layer feed-forward ANN with a back-propagation(BP) learning algorithm. The processing parameters of ageing treatment for hot extruded steel AerMet100 are optimized. And the optimum parameter ranges predicted by the network are ageing temperature of 450~458oC and ageing time of 6.3~8h. The ageing treatment temperature of 450?C for 8h are selected as a validated processing parameter for the hot extruded steel AerMet100, the measured mechanical properties based on the parameters mentioned above coincide commendably with predicted results.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Heat treatment > Heat treatment process > Special heat treatment > Aging treatment
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