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nanoprecipitation
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Development of Mechanical Properties of 420 AISI Martensitic Stainless Steel Using the Age Hardening Nano Precipitates and ANN Analysis
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
The Austenitization, influence of ageing condition and the prediction kinetics of AISI 420 martensitic stainless steel were studied in this paper. The Austenitizing temperature of 9200C, 9500C and 10200C were achieved. The specimens were heated for 15, 30 and 60 minutes then quenched in 250C Oil. The cooled samples were tempered at 2000C for 1 hour. The maximum tensile strength obtained at 10200C and 60 minutes were about 1800 MPa. The effect and ageing temperature and time on the strengthening behavior of this steel was modeled and analyzed by shear punch test and means of artificial neural networks (ANNs). Johnson-Mehl-Avrami-Kolmogorov (JMAK) analyses were applied to characterize the...
Fe Based SMA for Utilization of Damping Effect in Construction Structures and Effect of Nanostructural
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhaad, Khatiboleslam (Supervisor)
Abstract
To investigate the vibrational damping behavior (for application in construction structures) and shape memory effect of Fe based alloy, quaternary low carbon Fe-30Mn-6Si-6Cr alloy having small amounts of carbon and molybdenum were selected. The experimental samples were produced by melting of commercially pure raw materials and hot rolling, cold rolling and machining of the produced ingots. Nano-precipitation treatment was performed on a sample of specific composition. Chemical composition determination, cyclic tension-compression, simple bending, differential scanning calorimetry (DSC), micro hardness, and microstructural studies by optical and scanning electron microscopes (SEM) were...
The Evaluation of Microstructure and Mechanical Properties of a HSHR Stainless Steel Strengthen by Nano-Precipitates
, Ph.D. Dissertation Sharif University of Technology ; Karimi Taheri, Ali (Supervisor) ; Davami, Parviz (Co-Advisor)
Abstract
In this research, a computational method based on thermodynamic and physical metallurgy coupled by the d-electron approach was used to design the composition of a high strength and heat resistant (HSHR) stainless steel. Then, three series of the heat resistant 25Cr-35Ni-Nb (HP-Nb) stainless steels with tungsten, nitrogen, and micro alloying elements additions were cast. In these alloys a Nb/(C+ 6/7 N) ratio of ≈ 2.4 to 3.7 was chosen and they were directionally solidified under two cooling rates of 23 Ks-1 and 6 Ks-1. The effects of the alloy chemical composition and solidification cooling rate on the macrostructure, microstructure, microsegregation, and inclusions in the alloys were...