Effect of hot isostatic pressing processing parameters on microstructure and properties of Ti60 high temperature titanium alloy

Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.

活血散结中药复方含药血浆对PDGF干预下兔RPE细胞增殖的影响

目的:观察活血散结中药复方含药血浆对血小板源性生长因子(platelet derived growth factor,PDGF)干预下兔RPE细胞增殖的影响。方法:酶消化法获取RPE原代细胞,进行RPE细胞的原代培养和传代;制备活血散结中药复方含药血浆;选取第4代兔RPE细胞为实验细胞,PDGF低、中、高剂量(5、10、20μg/L)干预48h后,CCK-8法检测并选取适宜细胞实验干预浓度;建立PDGF干预下RPE细胞增殖模型。实验分组为空白对照组(DMEM)、正常血浆组、PDGF(10μg/L)组、PDGF(10μg/L)+AG1296(10μmol/L)组、PDGF(10μg/L)+10%含药血浆组,PDGF(10μg/L)+20%含药血浆组,分别加入相应处理因素干预24h后,Transwell法测定兔RPE细胞迁移力;而干预48h后,CCK-8法测定兔RPE细胞的细胞活力OD值。结果:10%和20%浓度的活血散结中药复方含药血浆能有效抑制PDGF干预下RPE细胞的细胞活力、细胞迁移。结论:活血散结中药复方含药血浆能够抑制PDGF干预下兔RPE细胞增殖,这可能是其有效治疗增殖性玻璃体视网膜病变的机制之一。

密蒙花滴眼液对去势雄兔干眼结膜炎性因子IL-1β和黏蛋白5AC及P38MAPK表达的影响

目的:观察不同浓度的密蒙花滴眼液对去势雄兔干眼结膜炎性因子IL-1β、黏蛋白5AC(MUC5AC)及P38MAPK表达的影响,从而探讨密蒙花滴眼液对干眼的疗效。方法:将36只雄兔随机分为:空白组、模型组、密蒙花滴眼液低浓度组(1mg/mL)、中浓度组(1.5mg/mL)、高浓度组(3mg/mL)、睾酮组。除空白组外各组均行睾丸及附睾切除建立干眼动物模型,造模成功后,空白组和模型组不予以处理,密蒙花滴眼液低浓度组(1mg/mL)、中浓度组(1.5mg/mL)、高浓度组(3mg/mL)给予密蒙花不同浓度滴眼液,3次/d,睾酮组按0.5mL/kg剂量在大腿肌肉处注射丙酸睾酮,每3d 1次,各组分别于造模前和用药4wk后在全身麻醉下检测荧光素染色、SchirmerⅠ试验(SⅠt)和泪膜破裂时间(BUT)。用药4wk后处死兔子,取其双眼球结膜组织,采用免疫组织化学染色法检测结膜中IL-1β、MUC5AC、P38MAPK的表达。结果:密蒙花滴眼液低浓度组、中浓度组、高浓度组用药4wk后,SⅠt值明显高于模型组,BUT值明显长于模型组,角膜荧光素染色阳性较模型组有明显改善(均P<0.01)。密蒙花滴眼液低浓度组、中浓度组、高浓度组结膜IL-1β、P38MAPK的阳性表达低于模型组,MUC5AC的表达高于模型组(P<0.01),密蒙花滴眼液高浓度组优于低浓度、中浓度组。结论:密蒙花滴眼液具有类雄激素效果,对于去势雄兔干眼可以下调干眼结膜组织中IL-1β、P38MAPK的表达,增加MUC5AC的表达,从而减少干眼结膜组织的炎症浸润,维持泪膜稳定性,但其作用弱于雄激素。密蒙花滴眼液中、高浓度组对于干眼治疗作用强于低浓度组,高浓度组优于中浓度组。

Research progress on refractory composition and deformability of shell molds for TiAl alloy castings

At present, most TiAl components are produced by an investment casting process. Environmental and economic pressures have, however, resulted in a need for the industry to improve the current casting quality, reduce manufacturing costs and explore new markets for the process. Currently, the main problems for investment casting of TiAl alloys are cracks, porosities, and surface defects. To solve these problems, many studies have been conducted around the world, and it is found that casting defects can be reduced by improving composition and properties of the shell molds. It is important to make a summary for the related research progress for quality improvement of TiAl castings. So, the development on refractory composition of shell molds for TiAl alloy investment castings was reviewed, and research progress on deformability of shell mold for TiAl alloy castings both at home and abroad in recent years was introduced. The existing methods for deformability characterization and methods for improving the deformability of shell molds were summarized and discussed. The updated advancement in numerical simulation of TiAl alloy investment casting was presented, showing the necessity for considering the deformability of shell mold during simulation. Finally, possible research points for future studies on deformability of shell mold for TiAl alloy investment casting were proposed.

Effect of initial deposition behavior on properties of electroless Ni-P coating on ZK60 and ME20 magnesium alloys

The composition of magnesium alloys is greatly associated with initial deposition behavior of electroless Ni-P coatings.Thus,the initial deposition behavior of electroless Ni–P coatings on ZK60 and ME20 alloys was investigated.The results indicated that differences in the alloy compositions significantly influenced the initial deposition process and the adhesive strength,corrosion resistance,and crystal structure.The initial deposition of coatings on ZK60 and ME20 alloys preferentially occurred on the precipitates.The precipitates in ZK60 alloy had higher chemical activity after HF activation and controlled the initial deposition rate of the coating.The initial deposition rate of the coating on ME20 alloy mainly depended on the density of the Mg F2 film formed by HF activation rather than on the precipitates.Owing to differences in the initial deposition process,the coating on ZK60 alloy had higher adhesive strength and better corrosion resistance than that on ME20 alloy.The coatings on ZK60 and ME20 alloys mainly had crystalline structures,and the coating on ME20 alloy had also a slight microcrystalline structure.

Effect of Nb and alloying elements on interface reaction between high Nb-containing TiAl alloys and ZrO_2-based ceramic moulds

In the present study, Ti-45Al-(6, 7, 8)Nb(at%) and Ti-45Al-8Nb-0.5(Mn, Si, Y, B) alloys were prepared by arc melting and casting into Zr O2(Y2O3 stabilized) ceramic moulds to study the effect of alloying elements Nb and Mn, Si, Y, B on the interfacial reaction between casting Ti Al alloys and ceramic moulds by SEM, and the elements' distribution in the interface reaction layer by line scanning. The results showed that with an increase in Nb content, the interfacial reaction weakened and the thickness of the reaction layer decreased gradually. The interface reaction thickness of the alloys with Nb content of 6, 7, 8at% were 60, 34 and 26 μm, respectively. Clearly, the addition of 8at% Nb to Ti-45 Al is the best for the thickness of the reaction layer. The addition of Nb would form a Nb-rich film in the reaction layer, which could reduce the solubility of oxygen in the interface, and suppress further diffusion of oxygen to the matrix. If the same content of Mn, Si, Y, or B alloying elements were added respectively to Ti-45Al-8Nb, the thickness of the interface reaction layer from large to small was as follows: Mn>Si>Y>B. The interface reaction thickness increased after 0.5at% Mn added, had no obvious change after 0.5at% Si addition, and decreased after adding 0.5at% Y or B. The introduced elements, which formed a protective film or/and promoted the formation of a dense aluminum oxide layer, would be of benefit to the resistance of interfacial reaction.