IMPROVED PROCESSING FOR MICROSTRUCTURES AND MECHANICAL PROPERTIES OF A COMMERCIAL PIPELINE STEEL

The transformation productions of hot-deformation simulation experiments were investigated using a Gleeble-1500 hot simulator for a commercial pipeline steel. Based on the investigation results, the improved thermo-mechanical control processing (TMCP) schedules containing a two stage multi-pass controlled rolling coupled with moderate cooling rates were applied to hot rolling experiments and acicular ferrite dominated microstructure was obtained. Microstructures and mechanical properties of hot rolled plates were related to TMCP processing, and regression equations describing the relation between processing parameters and mechanical properties in the current TMCP were developed, which could be used to predict mechanical properties of the experimental steel during commercially processing. It was found that with an increase in cooling rate after hot rolling, grain size in the microstructure became smaller, the amount of polygonal ferrite decreased and acicular ferrite increased, and accordingly mechanical properties increased.

Recent progress of grain boundary diffusion process for hot-deformed Nd-Fe-B magnets

Grain boundary diffusion process(GBDP)was first proposed for sintered Nd-Fe-B magnets to achieve the high utilization efficiency of heavy rare earth elements.Recent success of fabricating high performance nanocomposite magnets by GBDP indicates that this method also exerts huge applicable potential on hot-deformed Nd-Fe-B magnets.In this review,the development and magnetic property enhancement mechanisms of different diffusion methods proposed on hot-deformed magnets were thoroughly elucidated.Moreover,the improve room for further property enhancement and the accompanying problems of GBDP on hot-deformed magnets are also discussed in this article.

Synthesis of bulk lanthanum polyphosphate and other rare earth phosphates through hydrothermal hot-pressing

Bulk samples of lanthanum polyphosphate were synthesized through a hydrothermal hot-pressing(HHP)process.In this process,pressing temperature,pressure and volume of water were varied in order to improve the density and strength of the resulting materials.The strength of the bulk samples was estimated through drilling and ultrasonic treatments.In order to improve the strength of the materials,the use of microwave irradiation was examined.Lanthanum polyphosphate formed porous bulk samples with a filling factor of approximately 70%,which was calculated from real and theoretical densities.With respect to machinable strength,a drilled hole greater than 7.0 mm in diameter was obtained on some bulk samples,and the diameter of the samples was 14 mm.The HHP process is a useful method for obtaining bulk samples of lanthanum polyphosphate.Bulk lanthanum polyphosphate containing water crumbled easily to a powder form upon ultrasonication.However,these bulk samples retained their shape upon ultrasonication,despite containing water,after exposure to microwave irradiation,and also experienced minimal weight loss.Furthermore,to study the effect of microwave heating,bulk lanthanum orthophosphate,yttrium orthophosphate and polyphosphate were also examined.