Authors: Cheng Jia Shang, Y.T. Zhao, Xue Min Wang, L.J. Hu, Shan Wu Yang, Xin Lai He
Abstract: The influence of processing parameters on the acicular ferrite formation for the low
carbon microalloying steel was studied. The results showed that the fraction of acicular ferrite could be controlled by the cooling process. The acicular ferrite/ bainitic ferrite dual phase structure can be formed. The multi-phase microstructure is ultra fine. The hardness is sensitively affected by the acicular ferrite fraction.
85
Authors: Bum Rae Cho, Dae Hong Heo
Abstract: Porous mullite with a porosity of about 78% was fabricated using Al(OH)3, SiO2 and AlF3
powders to develop non-asbestos friction materials for brake pads. A mullite composite was
fabricated by infiltrating liquid phenolic resins to the porous mullite. The effects of the processing
parameters (infiltration frequency, immersion duration and resin temperature) on the properties of the
mullite composite obtained by the liquid infiltration technique were studied. SEM analysis reveals
that the parameters affected the degree of infiltration and hardness of the mullite composite by
changing the infiltration frequency and immersion duration. With increasing immersion duration and
infiltration frequency, the resultant porosity had lower values. In the case of hardness, the measured
values showed an opposite tendency.
105
Authors: J.S. Kang, S.S. Ahn, C.Y. Yoo, Chan Gyung Park
Abstract: In the present study, focused ion beam (FIB) technique was applied to make site-specific
TEM specimens and to identify the 3-dimensional grain morphologies of bainitic microstructure in
low carbon HSLA steels such as granular bainite, acicular ferrite and bainitic ferrite. Granular
bainite consisted of fine subgrains and 2nd phase constituents like M/A or pearlite located at grain
and subgrain boundaries. Acicular ferrite was characterized by an aggregate of ramdomly orientated
and irregular shaped grains. The high angle boundaries between adjacent acicular ferrite grains
caused by intragranular nucleation during continuous cooling process. Bainitic ferrite revealed
uniform and parallel lath structure within the prior austenite grain boundaries and its’ packet size
could effectively decreased by the formation of intragranular acicular ferrite.
73
Authors: Jian Er Zhou, Xiao Zhen Zhang, Jing Zhang, Yong Qing Wang, Shi Kai Zhao, Xi E Cai
Abstract: Porous acicular mullite ceramic was prepared by in-situ reaction sintering, using clay materials and Al (OH)3) as the raw materials. The influences of different clay materials on the phase composition, formation of acicular grains and microstructure of prepared porous ceramics were investigated. Results show that the metal oxide impurities were beneficial for the synthesis of acicular mullite. The prepared porous ceramic from Longyan kaolin with high impurity content has the highest mullite content of 93.5%, and composed of interlaced acicular grains with high slenderness ratio of 26.4 and large average diameter of about 0.7μm when sintered 1400°C for 2h. The TEM analysis indicates that the growth direction of acicular grains is along the [001] direction (c axis) of orthorhombic mullite crystals.
344
Authors: Shiang Cheng Jeng, Horng Shing Chiou
Abstract: The Ti-6Al-4V alloy were solution heat-treated at 960°C for 1 hour and then cooling by water-quenching immediately and 2 bar argon atmosphere, respectively. After being aged at 550°C for 5 hours, the tensile and Charpy impact test were performed. Based on the results, it is found that the quantity of primary α grains will increasing with decreasing the cooling rate following the solution heat treatment, and which will result in the tensile strength and toughness decreasing. Moreover, the optical and SEM micrographs indicated that the cracks propagated with traversing the prior β grains and propagating along the primary α grain boundaries in both of the tensile and impact fractured specimens. This implies that the strength of α grain boundary is less than that of α grain, which will play an important role on the mechanical properties of tensile strength and toughness.
103
