Preparation and potential application of functional ordered microstructures

With the development of science and technology,ordered microstructures with special functions have aroused intense research interest.These functional microstructures have been widely used in fields of microelectronic devices,micro-reactors,biochemical sensors and optical devices,etc.This paper summaries our work on preparation and application of microscopic patterned surfaces with ordered microstructures,and looks into the future development of this field.

Spectral narratives of microstructural restyling and their controls on hydrocarbon generation potential from coal

The low to medium-rank Tertiary coals from Meghalaya,India,are explored for the first time for their comprehensive micro-structural characterization using the FTIR and Raman spectroscopy.Further,results from these coals are compared with the Permian medium and high-rank coals to understand the microstructural restyling during coalification and its controls on hydrocarbon generation.The coal samples are grouped based on the mean random vitrinite reflectance values to record the transformations in spectral attributes with increasing coal rank.The aliphatic carbon and the apparent aromaticity respond sharply to the first coalification jump(R:0.50%)during low to medium-rank transition and anchizonal metamorphism of the high-rank coals.Moreover,the Raman band intensity ratio changes during the first coalification jump but remains invari-able in the medium-rank coals and turns subtle again during the onset of pregraphitization in high-rank coals,revealing a polynomial trend with the coal metamorphism.The Rock-Eval hydrogen index and genetic potential also decline sharply at the first coalification jump.Besides,an attempt to comprehend the coal microstructural controls on the hydrocarbon poten-tial reveals that the Tertiary coals comprise highly reactive aliphatic functionalities in the type I-S kerogen,along with the low paleotemperature(74.59-112.28℃)may signify their potential to generate early-mature hydrocarbons.However,the presence of type II-II admixed kerogen,a lesser abundance of reactive moieties,and overall moderate paleotemperature(91.93-142.52℃)of the Permian medium-rank coals may imply their mixed hydrocarbon potential.Meanwhile,anchizonal metamorphism,polycondensed aromatic microstructure,and high values of paleotemperature(~334.25 to~366.79℃)of the high-rank coals indicate a negligible potential of producing any hydrocarbons.

Effect of Multi-Pass Equal Channel Angular Pressing on the Microstructure and Mechanical Properties of a Heterogeneous Mg_(88)Y_8Zn_4 Alloy

The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4（in at.%） alloy during multi-pass equal channel angular pressing（ECAP） were systematically investigated in this work.The results show that four phases,i.e.α-Mg,18 R long period stacking ordered（LPSO） phase,Mg24Y5 and Y-rich phase,are present in cast alloy.During ECAP,dynamic recrystallization（DRX） occurs and the diameter of DRXedα-Mg grains decreases to 0.8 μm.Moreover,precipitation of lamellar 14 H LPSO structure is developed withinα-Mg phase.Both the refinement of α-Mg grains and precipitation of 14 H LPSO contribute to the increase in micro-hardness from 98 HV to 135 HV for α-Mg.In addition,a simplified model describing the evolution of 18 R LPSO phase is established,which illustrates that 18 R undergoes a four-step morphological evolution with increasing strains during ECAP,i.e.original lath → bent lath → cracked lath → smaller particles.Compression test results indicate that the alloy has been markedly strengthened after multi-pass ECAP,and the main reason for the significantly enhanced mechanical properties could be ascribed to the DRXed α-Mg grains,newly precipitated 14 H lamellas,18 R kinking and refined 18 R particles.

Evolution of Microstructure and Ordering in Rolling Process of Fe-6. 5 mass% Si Alloy

Fe-6. 5 mass% Si alloy is an excellent soft magnetic material with good application prospects. After rolling,the structure of the sheet is likely to be heterogeneous along the normal direction. The microstructure and ordering evolution in the thickness range of the sheets during hot-warm rolling process was studied by means of optical microscope and transmission electron microscope. The results show that dynamic recrystallization occurs in the surface parts during the hot and warm rolling processes,where the grains are equiaxed but have high density of dislocations due to the large deformation. The grains in the center part are elongated along the rolling direction. It is also found that in the hot rolled sheet,the center part has lower density of dislocations because of dynamic recovery. Meanwhile,this part has higher ordering content compared with the surface part,indicating that the high density of dislocations can inhibit the formation of ordering in the air cooling process after hot rolling. In the warm rolling process,both of the parts are deformed heavily. Large deformation destroys ordered phases and induces disordering. The ordering content is low in the whole warm rolled sheet.

Effect of Cryogenic Treatment on Deformation Behavior of As-cast AZ91 Mg Alloy

The as-cast AZ91 Mg alloy samples were cryogenic treated with different time. Otherwise, optical microscope （OM）, mechanical test, resistance test and XRD analysis were used to research the microstructure evolution and physical variation of the samples before and after cryogenic treatment （CT）. Due to CT, the structure of as-cast AZ91 Mg alloy was changed from disordered solid solution to ordered solid solution. Firstly, the appearance of ordered solid solution leads to the improvement of peak stress after CT, because of ordered strengthening. Secondly, resistance and crystallographic lattice constant of the samples reduce obviously. Otherwise, the frame-type twinning which is created from matrix in the cryogenic environment could hinder the twin growth and cause the ordered strengthening.

Effect of 0.5 mass% Cu Addition on Ductility and Magnetic Properties of Fe-6.5Si Alloy

The effect of adding 0.5mass% Cu on ductility and magnetic properties of Fe-6.5Si（mass%）alloy was investigated.The alloys with and without 0.5mass% Cu addition were warm rolled into thin sheets of thickness no more than 0.3mm at temperature below 600 ℃.It was found that the alloy with 0.5mass% Cu addition was more easily warm rolled than Cu-free alloy.Tensile tests were carried out to further investigate this phenomenon,which confirmed that the ductility of the alloy with 0.5mass% Cu addition was significantly higher than that of Cu-free alloy at 550 ℃.Based on the results of transmission electron microscopy analysis,the ductility increase of the alloy with 0.5mass% Cu addition was attributed to the effect of Cu on the promotion of dynamic recovery and suppression of long-range order in the alloy during warm rolling process.It was also observed that the iron loss was lower and inductance was higher for the alloy with 0.5 mass% Cu addition.Thus,it can be concluded that adding a suitably small amount of Cu would not only increase the ductility of Fe-6.5Si alloy at warm rolling temperatures but also improve its magnetic properties.