Microstructure and mechanical properties of a low activation cast WTaHfTiZr refractory high-entropy alloy

In the face of the requirement that nuclear fusion reactor materials exhibit more excellent thermal,mechanical and physical properties,a novel refractory highentropy alloy,WTaHfTiZr was proposed.The constituent elements were selected in consideration of low activation,high melting point and high thermostability.The alloys were prepared by arc melting.The as-cast alloy shows a dendrite microstructure with two disordered BCC phases,which caused by the preferential nucleation of W and Ta with much higher melting points during solidification.It exhibits a high compressive yield strength of 1,900 MPa and fracture strain of 8.1% at room temperature,and its yield strengths are up to 612 MPa at 700 ℃ and 203 MPa at 1,000 ℃,respectively.The high strengths are attributed mainly to solid solution strengthening and second phase strengthening.This alloy shows great promise as one of the next-generation nuclear fusion reactor materials.

Genotoxic and Biological Evaluation of a Nano Silica Cross Linked Composite Specifically Used for Intra-Vas Device

The Context: Aims: To evaluate the biocompatibility and in vitro genotoxicity of a non-copper nano silica polymer modified composite for filtering-type intra-vas devices. Settings and Design: Academic research laboratory, Huazhong University of Science and Technology. Prospective experimental study. Methods and Material: Non-copper nano silica polymer modified composite rods were implanted into the back muscle of rabbits for biocompatibility evaluation. Comet assay was applied to the determination of DNA damage, while, Mutagenic activity was tested by means of Ames test using Salmonella typhimurium TA98 and TA 100 tester strains with and without metabolic activation. Statistical analysis used: qualitative and quantitative data were tested using the Chi-square test and Student’s test. Results: Only mild inflammatory reaction was observed in the surrounding tissues of the implanted nano-silica modified polymer composite in the early implantation stage, which was similar to that of the sham-operated group. The inflammatory reaction was completely disappeared after 12 weeks. No significant DNA damage (P > 0.05) were tested on the nano-silica modified polymer composite in Comet assay. In Ames test, the extracts from non-copper composite did not exert mutagenic effect on the bacterial. Conclusions: The non-copper nano silica modified composite did not exhibit in vitro genotoxicity and obvious inflammation in tissue, it would be a safe biomaterial for further clinical trial.

Bending mechanical properties of W/TiN/Ta composites with interfacial TiN coatings

Tungsten is one of best candidates for plasma facing materials(PFMs)in fusion reactors.But its application in fusion areas is strongly restricted by the inherent brittleness and high ductile-brittle transition temperature.To improve the toughness of W-based materials,W/TiN/Ta-laminated composites were fabricated by spark plasma sintering.Three-point bending test was performed to investigate the bending mechanical properties.Multiple crack propagation is the main crack propagation mode in W/TiN/Ta composites.Energy dissipation by interfacial debonding and crack deflection at interfaces as well as crack bridging by Ta foils and plastic deformation of Ta can contribute to the toughening of W/TiN/Ta composites.The existence of interfacial TiN coatings can act as weak points and promote interfacial debonding.TiN coatings with(111)preferred orientation are found to be conducive to the strengthening of W/TiN/Ta composites.

Low-temperature mechanical and magnetic properties of the reduced activation martensitic steel

Mechanical and magnetic properties as well as their relationship in the reduced activation martensitic （RAM） steel were investigated in the temperature range from -90℃ to 20℃. Charpy impact tests show that the ductile-to-brittle transition temperature （DBTT） of the RAM steel is about -60℃. Low-temperature tensile tests show that the yield strength, ultimate tensile strength and total elongation values increase as temperature decreases, indicating that the strength and plasticity below the DBTT are higher than those above the DBTT. The coercive field （Hc） in the scale of logarithm decreases linearly with the increasing temperature and the absolute value of the slope of InHc versus temperature above the DBTT is obviously larger than that below the DBTT, also confirmed in the T91 steel. The results indicate that the non-destructive magnetic measurement is a promising candidate method for the DBTT detection of ferromagnetic steels.