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Zr-Y modified silicide coating was deposited on TC4 alloy by the pack cementation process. The microstructure， friction and wear performance， and wear mechanisms of the coating were investigated. The results show that the Zr-Y modified silicide coating has a multi-layer structure， an outer layer consists of TiSi2 and a small amount of ZrSi2， a thin middle layer is TiSi， and an inner layer is a mixture of Ti5Si4 and Ti5Si3. The micro-hardness of the coating is much higher than that of the TC4 substrate and exhibits an obvious decrease tendency from the surface to the interior. The Zr-Y modified silicide coating possesses good anti-wear performance when wearing against GCr15 and Al2O3 balls at a high-temperature of 600 ℃. When wearing against GCr15， the wear rate of the coating is about 3.59×10-5 mm3/（N·m）， which is about 36.6% of that of the TC4 substrate， and the main wear mechanisms are characterized by the adhesive of GCr15 on the coating surface and oxidation wear. When wearing against the Al2O3 ball， the wear rate of the coating is about 9.75×10-5 mm3/（N·m）， which is about 18.9% of that of the TC4 substrate， and the wear mechanisms are fatigue wear， oxidation wear， and adhesion wear.

This study aims to investigate the effects of five plant polysaccharides from Radix Astragalus, Rhizoma Atractylodis, Radix Scrophulariae, jujubes, Fructus mume on intestinal microorganisms and their metabolites in patients with type 2 diabetes mellitus (T2DM) by using high-throughput sequencing, metabolomic techniques and an in vitro fermentation model. The results showed that plant polysaccharides could significantly improve the structure of the intestinal flora in diabetic patients, and all five polysaccharides could enrich Faecalibacterium and Roseburia and inhibit Escherichia. Plant polysaccharides could regulate the contents of gas medium and short-chain fatty acids, and change the metabolic pathways of amino acids and short-chain fatty acids in the intestinal flora of patients with T2DM. Radix Astragalus, Atractylodis Rhizoma and Radix Scrophularia polysaccharides had significant regulatory effects on the total amount of short-chain fatty acids, and could also regulate the contents of acetic acid, propionic acid, butyric acid, valeric acid, isobutyric acid and isovaleric acid. In addition to these polysaccharides, jujube polysaccharide also increased the content of total gaseous media as well as CO2 and CH4 in patients with T2DM, while Fructus mume polysaccharide could reduce the contents of gas medium and H2S. These results provide a theoretical basis for the screening and utilization of plant polysaccharides and understanding their targeted regulation of intestinal microorganisms.

In this work, the microstructure evolution of the Nb-12Si-22Ti-14Cr-2Al-2Hf alloy (at.%) fabricated by liquidmetal-cooled directional solidification (LMC) was investigated and the solidification behaviors were discussed. The results revealed that the growth rate was of crucial in controlling the microstructure of this alloy and the higher growth rate was beneficial to the formation of metastable phase Nb3Si. The microstructure of non-melted region consisted of NbSS dendrites, NbSS/Nb5Si3 eutectics and Ti-rich NbSS/Cr2Nb eutectics while the microstructure of quasi-steady-state growth region of this alloy consisted of NbSS dendrites, Nb3Si laths and Ti-rich NbSS/Cr2Nb eutectic. Nb3Si had the advantage of nucleation at medium/high growth rate. Therefore, the microstructure evolution occurred in this study was owing to the increase of growth rate.

An Nb-14Si-22Ti-4Cr-2Al-2Hf-0.15Y(at.%) alloy was prepared by directional solidification (DS) with liquid metal cooling, and the withdrawal rates selected were 1.2, 6, and 18 mm·min-1, respectively. The Influence of withdrawal rate and heat treatment on the microstructural evolution, fracture toughness and tensile strength at room temperature were investigated. Results show that the directionally solidified microstructure is composed of primary (Nb, X)ss dendrites and (Nb, X)ss/α-(Nb, X)5Si3 eutectic cells aligning with the growth direction. The formation of bulk Nb3Si is suppressed. With an increase in withdrawal rate, the dendrite arm spacing of (Nb, X)ss decreases, and the (Nb, X)ss/α-(Nb, X)5Si3 eutectic cells become finer and distribute homogeneously. Directional solidification can significantly improve the room temperature fracture toughness, especially the alloy with a withdrawal rate of 6 mm·min-1; its average value reaches 14.1 MPa·m0.5, about 34% higher than that of the alloy without directional solidification. The withdrawal rate has obvious effect on tensile strength, and the tensile strength is improved from 200 MPa to 429 MPa as the withdrawal rate increases from 1.2 mm·min-1 to 1.8 mm·min-1. After heat treatment, the primary (Nb, X)ss branches become coarser; both the room temperature fracture toughness and tensile strength of the alloys solidified at 1.2 and 6 mm·min-1 are somewhat lower than the corresponding values of the alloy without heat treatment, while they are higher than the corresponding values of the alloy without heat treatment when solidified at 18 mm·min-1.

In this work, an Nb-14Si-24Ti alloy (at.%) was prepared by liquid-metal-cooled directional solidification (DS) and then heat treated (HT) at 1450°C for 100 h. The effects of the withdrawal rate and heat treatment on the microstructure were investigated. The results show that the DS samples consisted of NbSS dendrites, Nb3Si blocks and eutectic NbSS/Nb3Si. As the withdrawal rate increased, the microstructure became finer, the volume fraction of eutectic NbSS/Nb3Si increased and the morphology of eutectic cell transformed from petaloid to regularly arranged granular morphology. The microstructure of the HT samples consisted of NbSS and Nb3Si. The metastable phase of Nb3Si did not discompose through the eutectoid reaction. The dendritic NbSSconnected through diffraction and the secondary dendrite arm got coarser. The boundary of eutectic NbSS/Nb3Si became blurry and the black Ti-rich phase of the DS samples in this region disappeared. The Nb3Si connected to form the continuous matrix. The granular NbSS of eutectics spheroidized and the lamellar NbSS of eutectic interconnected and became more bending distributed uniformly in the Nb3Si matrix.

The Y2O3 crucibles were introduced in the study as an alternative to the traditional ceramic ones in vacuum induction melting of multi-component Nb-16Si-22Ti-2Al-2Hf-17Cr (at.%) alloys, to reveal the possible interactions between the alloy melt and the refractory crucible. Multiple melting time lengths and two cooling schemes were designed and used for the experiments. The chemical composition and microstructure of the tested alloy and the melt-crucible interaction were investigated and evaluated. In the experiments, Y2O3 crucible displays good physical-chemical compatibility. The results indicate that the increment of O element in the as-cast ingot is 0.03at.%-0.04at.% (72-97 ppm) and the increment of Y element is very insignificant. The key features of the alloy melt interacting with Y2O3 ceramics are analyzed and concluded in the paper. As a result of the dissolution reaction xY2O3 (in molten alloy) + (1-x)HfO2 (impurity) →Hf1-xY2xO2-x, a continuous double-layer solid film consisted of HfO2 solid solution (~2 μm) and pure HfO2 (~5 μm) is formed on the surface of the test ingot after cooled down in the crucible. The experimental results show that the Y2O3 crucible is applicable to the vacuum induction melting of Nb-Si based alloys.