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2. Master Thesis / Tesis Master
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Title:	Kesan penambahan Cu dan Ni pada sifat tegangan keluli fasa duaan untuk kegunaan otomotif
Authors:	Handra Nofriady. (P41077)
Supervisor:	Dr. Syarif Junaidi
Keywords:	Steel Automobile. Automotive industry
Issue Date:	1-Jul-2011
Description:	Dual phase steel is becoming more important in the automotive industry, because high strength and high ductility of the steel permit weight reduction of automotive vehicle without sacrificing formability of the steel. The dual phase steel which microstructure consists mainly of ferrite and martensite are an excellent choice for applications where low yield strength, high tensile strength, continuous yielding and good uniform elongation are required. In this study, effects of substitutional alloying elements such as of Cu and Ni on microstructures and tensile properties of the dual phase steel were investigated in order to improve mechanical properties of the dual phase steel. Materials are used in this study consist Fe-0.1 mass% C alloy (base steel), 1 mass% Ni added Fe-0.1% C alloy (Ni steel), and 1 mass% Cu added Fe-0.1% C steel (Cu steel). The samples were subjected to solution treatment at 1273K for 1.8ks and water quenching. As-quenched steels were subjected to annealing at various temperatures to obtain 20 vol.%, 50 vol.% and 80 vol.% of martensite and water quenching. Temperatures for annealing were determined using JMatPro 4.1 software. Tensile test was done by an Instron Universal Testing Machine with a 30 kN load capacity. Hardness of the samples were measured using a microhardness tester with a applied load of 19.6 N (2 kgf). Microstructures were observed by the optical microscopy (OM), Scanning Electron Microscopy (SEM) and X-Ray Diffratolametry (XRD). Asquenched samples exhibit a typical lath-martensitic structure. It is found that addition of substitutional elements can increase hardness of martensitic structure. The samples were annealed to obtain austenite and ferrite at dual phase region and then water quenched to obtain martensite and ferrite at ambient temperatures. Microstructures of the materials at various annealing temperatures consist of ferrite and martensite structures. Hardness of samples increases with increasing vol.% of martensite. It is also found that hardness of the Ni steels and the Cu steels higher than that of the base steel in all martensite contents. Result of tensile test shows that yield stress and uniform elongation is independent of addition of substitutional elements. Nevertheless, tensile stress and total elongation are increased owing to the elements. It should be noted that an index of strength and ductility, i.e. TSUE is improved with addition of substitutional elements. It is known that increase of tensile stress is due to effect of dislocation strengthening. In order to investigate increase of dislocation strengthening due to addition of elements, dislocation densities of steels are calculated by the Hall method. The dislocation densities increased with increasing martensite content. Moreover, the dislocation densities of the Ni steel and the Cu steel are higher than those of the base steel in whole martensite contents. Thus, the tensile strength and TSUE can be improved the with addition of the element. In conclusion, the experiment show that an increase in vol.% of martensite will increase the strength without sacrificing the ductility. The addition of Cu and Ni also improves the tensile properties of the dual phase steels.,Sarjana
Pages:	105
Call Number:	TA472 .H267 2011 3
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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