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Carbon fiber reinforced thermoplastics (CFRTP) have been developed to realize excellent formability and mechanical properties. Specifically, discontinuous CFRTP (DCFRTP) are promising candidates for decreasing production cost and for application to mass production. Polyamide 6 (PA6) is a promising matrix for CFRTP due to its good adhesion properties with carbon fibers (CFs). However, the degradation of the mechanical properties of CFRTP due to the hygroscopic properties of PA6 is an area of concern. Thus, an investigation of the effects of water absorption on the mechanical properties of discontinuous CF reinforced PA6 is necessary. Additionally, a theoretical prediction of the degradation in mechanical properties is useful to clarify the effect of the absorbed water. Therefore, in this study, the influence of water absorption on the mechanical properties of CFRTP was investigated by measuring the mechanical properties using a three-point bending test. In addition, the flexural modulus was calculated using the Timoshenko beam equation to predict the degradation due to water absorption.

Oxide dispersion strengthened austenitic stainless steel (ODS316), which is based on advanced SUS316 steel, has been developed by mechanically alloying and hot extrusion. Hafnium and titanium were added to make a fine distribution of oxide particles. The stability of oxide particles dispersed in ODS316 under irradiation was evaluated after 250 keV Fe+ irradiation up to high doses at 500 °C. TEM observation and EDS analysis indicated that fine complex oxide particles with Y, Hf and Ti were mainly dispersed in the matrix. There are no significant changes in the distribution and the size of oxide particles after irradiation. It was also revealed that the constitution ratio of Ti in complex oxide appeared to be decreased after irradiation. This diffuse-out of Ti during irradiation could be explained by the difference in oxide formation energy among alloying elements.

From the irradiation resistance and high-temperature strength, oxide dispersion strengthened (ODS) ferritic steels are candidate materials for advanced and fusion reactors. For the development of advanced steels the key issue is to homogenize nano-particles into matrix. Recent studies have indicated that Ti addition can homogenize Y-Ti complex particles into ferrite matrix, but the reason of the effect of additional elements has not been clarified. In this model study, we focus on the effect of additional elements, such as IV and V families and other oxide formers, which can control potentially the distribution of the oxide particles. The materials used in this study were based on Fe-9Cr-Y{sub 2}O{sub 3} alloys which were mechanical alloyed (MA) from the powder of Fe, Cr and Y{sub 2}O{sub 3}, which was added systematically with the element of Ti, Zr, Ta, V, Nb, Hf, Al, Si and others. Usually ODS fabrication process is required for hot extrusion, but we annealed up to 1150 C for simplify the microstructure. To evaluate the distribution of ODS particles; we used TEM equipped with EDS after electro-polishing or FIB techniques. (1) In the case of Si or Al addition, oxides were disappeared after MA process, which means Y{sub 2}O{sub 3}more » and other elements should be in solution at non-equilibrium condition. Two types of oxides of Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} or SiO{sub 2} developed after the annealing at 850 C, but only complex oxides were developed after the annealing at 1150 C. This result suggests that the oxide formation is independent process for Y and Si or Al. (2) In the case of Ti addition, oxides also were disappeared after MA process, but developed after annealing at 1150 C. This means that Ti can stabilize complex oxides of Y and Ti, and enhance the fine distribution of the oxides comparing with simple Fe-9Cr-Y{sub 2}O{sub 3} alloy. (authors)« less