Roslina Mohammad

Fatigue properties of JIS H3300 C1220 copper for strain life prediction

The existing methods for estimating strain life parameters are dependent on the material’s monotonic tensile properties. However, a few of these methods yield quite complicated expressions for calculating fatigue parameters, and are specific to certain groups of materials only. The Universal Slopes method, Modified Universal Slopes method, Uniform Material Law, the Hardness method, and Medians method are a few existing methods for predicting strain-life fatigue based on monotonic tensile material properties and hardness of material. In the present study, nine methods for estimating fatigue life and properties are applied on JIS H3300 C1220 copper to determine the best methods for strain life estimation of this ductile material. Experimental strain-life curves are compared to estimations obtained using each method. Muralidharan-Manson’s Modified Universal Slopes method and Baumel-Seeger’s method for unalloyed and low-alloy steels are found to yield batter accuracy in estimating fatigue life with a deviatio...

Microstructural Study of Newly Designed Ti-6Al-1Fe Alloy through Deformation

Recently, iron (Fe) is introduced to substitute vanadium (V) in Ti-alloy. Therefore, new (α+β) titanium alloy, Ti-6Al-1Fe was designed through a complete replacement of V by Fe with major composition modifications of Ti-6Al-4V. This new alloy is believed could provide similar properties of Ti-6Al-4V through modification of its microstructures. Different heat treatments can lead to a diversity of microstructural permutations and combinations. Thus, it is very crucial to study in-depth understanding about the microstructure of Ti-6Al-1Fe. Results reveal that the microstructure of as-received alloy is a typical fine lamellar microstructure. The bi-modal microstructure can be obtained by hot rolling below beta-transus temperature (Tβ) followed by recrystallization treatment at 925°C. While cold rolling followed by recrystallization treatment at 925°C produce equiaxed microstructure.

Behaviour of T91 Steel Oxide Scale Exposure to Temperature at 540°C for Different Exposure Duration

Grade T91 steel is one of a common material used for construction of superheater tubes in power generation boiler. In general, superheater tubes that operates in subcritical boiler are expose to operating temperatures in the range between 540°C to 580°C. Exposure to high temperature makes this steel subject to formation of oxide scale which can cause detrimental effect on the material properties. Excessive formation of oxide scale on internal surface of superheater tube can cause overheating damage at early stage of the boiler operation. This study was conducted to examine the behaviour of oxide scale forms on T91 steel for specimens exposed to temperature of 540°C for 200, 400, 600, 800 and 1000 hours holding time. The oxidation kinetic was identified as parabolic and the oxide scale was observed having 3 different layers which are haematite (Fe2O3), magnetite (Fe3O4) and spinel (Fe,Cr)2O3. The oxide scales layers were observed separated by voids and crack which are growing in size over time.