Papers by Keyword: Microstructural Feature

Abstract: Studies on the weldability of ferritic stainless steel grades suggests that low heat input rate and better heat transfer dynamics are appropriate for the control of grain size and microstructural feature in thin sections. However, the optimal welding conditions to achieve combination of such characteristics are yet to be established. In the present investigation, AISI 430 ferritic stainless steel is TIG welded using energy input between 0.205 and 2.05kj/mm and characterized in terms of microstructure and hardness. The microstructural characterization of the welds with varying heat input rates suggests the presence of interdendritic martensite in the fusion zone and grain boundary martensite in the HAZ in conjunction with some intermetallics in varying proportion. The hardness values across the welds indicate that grain growth and the presence of intermetallics are minimized when welded with increased heat input rates that permits transformation within the dual phase regions. The study provided a new insight into the contribution of heat input rate in the production of unwanted weld microstructural features and assisted in the design of methods and techniques for tailoring weld microstructures with optimum properties.

Abstract: The first-principles calculation based on density functional theory has been carried out to study the microstructural feature of the novel 24R-type long period stacking ordered structure in Mg₉₇Zn₁Y₂ alloy. The lattice positions of the Y and Zn atoms are determined theoretically, it is shown that the additive atoms are firstly enriched in the stacking fault layers at the two ends, a small amount are distributed in the interior stacking fault layers of the structure. And the arrangement of these Y and Zn atoms trends to be along the diagonal line of the unit cell. The structural stability is analyzed and the electronic density of state is discussed as well as.

Abstract: Micro-structural change caused by the corresponding change in creep properties of Cu-8.5at.%Al alloy was studied. It was found that a micro-structural observations reveal the formation of different types of defect features during creep of the investigated alloy at intermediate temperatures between 0.46-0.72Tm, where Tm is the absolute melting point. SEM was used to characterize the studied alloy by quantitative micro-analysis. It allowed the observer to defect the micro-structural features such as dislocation that were generated from deformation and could move interagranularly by glide and climb. Clearly, the development of this microstructure could be attributed to the grain refining effect of the Al indicating the role of the applied stress at this alloy. The results show that the creep rupture strength of Cu-8.5at.%Al alloy in the power law creep damage mechanism. This due to the constraint introduced on the matrix creep flow by the Al phase rather than the devolvement of high threshold stress values. While the increase in the length of Al filaments and reduction in interfilament spacing with increasing draw ratio increase the constraint on the creep flow of the matrix, they also enhance the creep damage caused by the diffusion mechanisms because of the easy diffusion paths along the Al filaments and the reduction in the matrix grain size.