Oxygen variation in titanium powder and metal injection molding

The control of oxygen is paramount in achieving high-performance titanium(Ti)parts by powder metallurgy such as metal in-jection molding(MIM).In this study,we purposely selected the Ti and Ti-6Al-4V powders as the reference materials since these two are the most representative Ti materials in the industry.Herein,hydride-dehydride(HDH)Ti powders were pre-oxidized to examine the ef-fect of oxygen variation on the characteristics of oxide layer on the particle surface and its resultant color feature.The results indicate that the thickness and Ti oxide level(Ti^(0)→Ti^(4+))of the oxide layer on the HDH Ti powders increased as the oxygen content increased,lead-ing to the transition of color appearance from grey,brown to blue.This work aids in the powder feedstock selection at the initial stage in powder metallurgy.In addition,the development of oxygen content was comprehensively studied during the MIM process using the gas-atomized(GA)Ti-6Al-4V powders.Particularly,the oxygen variation in the form of oxide layer,the change of oxygen content in the powders,and the relevant parts were investigated during the processes of kneading,injection,debinding,and sintering.The oxygen vari-ation was mainly concentrated in the sintering stage,and the content increased with the increase of sintering temperature.The variation of oxygen content during the MIM process demonstrates the crucial role of powder feedstock and sintering stage in controlling oxygen con-tent.This work provides a piece of valuable information on oxygen detecting,control,and manipulation for the powder and processing in the industry of Ti and its alloys by powder metallurgy.

Solvent de binding of water soluble binder in powder injection moulding

The solvent debinding of water soluble binder in powder injection moulding (MIM) was investigated systematically, including the effects of solvent types, temperature and the thickness of green parts on the solvent debinding rate. After studying the debinding of a green part with a thickness of 4.26 mm, it was found that, the debinding rate of polyethylene glycol(PEG) in water and alcohol was high initially, and then decreased; however, it would increase with temperature increasing. At room temperature, the dissolution rate of PEG in water was higher than that in alcohol, but the latter would be much faster with temperature increasing because the debinding activation energy in alcohol was 51.44 kJ·mol -1 ·K -1 , much higher than 24.23 kJ·mol -1 ·K -1 in water. With a green part thickness larger than 4.26 mm, the debinding was controlled by diffusion; but with that smaller than 2.36 mm, the debinding was controlled by both dissolution and diffusion.

Powder injection molding of pure titanium

An improved wax-based binder was developed for powder injection molding of pure titanium. A critical powder loading of 69 vol.% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding, and sintering process were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere （10^-3 Pa）. The mechanical properties of as-sintered specimens were less than those of titanium made by the conventional press-sintering process. Good shape retention and ±0.04 mm dimension deviation were achieved.

NUMERICAL SIMULATION OF FEEDSTOCK MELT FILLING IN A CYLINDRICAL CAVITY WITH SOLIDIFICATION IN POWDER INJECTION MOLDING

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KINETIC MODEL FOR POWDER INJECTION DESULFURIZATION

The kinetic model for desulfurization using CaO-based powder injection has been proposed, which accords with the actual process of the experiment. For the model, a comparison between CaO-based flux and Mg-based flux was made and the results show that the desulfurization rate of the Mg-based flux is far more than that of CaO-based flux. On the basis of the model calculation, on comparison of CaO-CaF2 flux and calcium aluminate flux, the desulfurization rates of the two fluxes are close to each other. In addition, the effects of some operational factors on the kinetics of desulfurization are discussed.

Clinical Non-inferiority Trial on Treatment of Coronary Heart Disease Angina Pectoris of Xin-blood Stasis Syndrome Type with Lyophilized Salvia Salt of Lithospermic Acid Powder for Injection

Objective： To evaluate the effectiveness and safety of lyophilized Salvia salt of lithospermic acid powder for injection （SSLA） in treating coronary heart diseases angina pectoris （CHD-AP） of Xin-blood stasis syndrome type, and to conduct the non-inferiority trial with Danshen injection （丹参注射液, DSI） as positive control. Methods： An non-inferiority clinical layered, segmented, randomized, and blinded trial on three parallel and multiple centered groups was conducted in 480 patients with stable effort angina grade Ⅰ , Ⅱand Ⅲ, who had two or more times of attack every week. The 240 patients in test group A were treated with SSLA 200 mg added in 250 ml of 5% glucose solution for intravenous dripping every day; the 120 patients in test group B were treated with SSLA but the dosage doubled; and the 120 patients in the control group were treated with DSI 20 ml daily in the same method as SSLA was given. The clinical effectiveness and safety were evaluated after the patients were treated for 14 days. Results： The results showed that the markedly effective rate in test groups A, B and control group was 37.45 %, 36.75 % and 30.09 % respectively, while the total effective rate in them was 88.09%, 89.74% and 67.26% respectively. Statistical significance was shown in comparisons of the therapeutic effect between control group with test group A and test group B, with that in the two test groups superior to that in the control group, and non-inferiority trial showed eligibility （P〈0.01）. Adverse reaction appeared in 8 patients in the test groups and 2 in the control group. Conclusion： SSLA has definite therapeutic effect in treating patients with CHD-AP, with its effect not inferior to that of DSI, and no evident toxic-adverse reaction.

Preparation of high nitrogen and nickel-free austenitic stainless steel by powder injection molding

High nitrogen and nickel-free austenitic stainless steel has received much recognition worldwide because it can solve the problem of ＂nickel-allergy＂ and has outstanding mechanical and physical properties. In this article, 0Cr17Mn11Mo3N was prepared by powder injection molding （PIM） technique accompanied with solid-nitriding. The results show that the critical solid loading can achieve up to 64vol% by use of gas-atomized powders with the average size of 17.4 μm. The optimized sintefing conditions are determined to be 1300℃,2 h in flowing nitrogen atmosphere, at which the relative density reaches to 99% and the N content is as high as 0.78wt%. After solution annealing at 1150℃for 90 rain and water quench, the 0.2% yield strength, ultimate tensile strength （UTS）, elongation, reduction in area, and hardness can reach as high as 580 MPa, 885 MPa, 26.0%, 29.1%, and Hv 222, respectively.

Injection molding of nano structured 90W-7Ni-3Fe alloy powder prepared by high energy ball milling

Blended elemental 90W 7Ni 3Fe (mass fraction, %) powder was mechanically alloyed in a planetary ball mill. Nano crystalline grains were obtained after 10 h milling. The nano structured powder was processed to full density by metal injection molding approach. Compacts from the optimal powder binder mixture were studied for molding and sintering behaviors. Milling significantly increases the maximum powder loading and homogeneity of the feedstock, and enhances the sintering densification process. When solid state sintered at 1 350～1 450 ℃, the alloy shows very fine grains (～3 μm), high tensile strength (>1 130 MPa) and almost no distortion. [

Effects of heat treatment on the properties of powder injection molded AlN ceramics

The effects of two different heat-treatment atmospheres,nitrogen atmosphere and reducing nitrogen atmosphere with carbon,on the properties of Y2O3-doped aluminum nitride（AlN） ceramics were investigated.The AlN powder as a raw material was synthesized by self-propagating high-temperature synthesis（SHS） and compacts were fabricated by employing powder injection molding technique.The polymer-wax binder consisted of 60 wt.% paraffin wax（PW）,35 wt.% polypropylene（PP）,and 5 wt.% stearic acid（SA）.After the removal of binder,specimens were sintered at 1850°С in nitrogen atmosphere under atmospheric pressure.To improve the thermal conductivity,sintered samples were reheated.The result reveals that the heat-treatment atmosphere has significant effect on the properties and secondary phase of AlN ceramics.The thermal conductivity and density of AlN ceramics reheated in nitrogen gas are 180 W·m^-1·K^-1 and 3.28 g·cm^-3 and the secondary phase is yttrium aluminate.For the sample reheated in reducing nitrogen atmosphere with carbon,the thermal conductivity and density are 173 W·m^-1·K^-1 and 3.23 g·cm^-3,respectively,and the secondary phase is YN.

Powder injection molding of Fe-Ni soft magnetic alloys

With miniaturization and complication of the shape of electronic devices in recent years,powder injection molding(PIM)seems to be a suitable process for fabricating the higher performance soft magnetic components.In this paper,high quality Fe-50Ni soft magnetic alloy was fabricated by PIM with carbonyl iron and nickel,and the effect of sintering process on its microstructure and magnetic properties were investigated.The mechanical and magnetic properties can be obviously improved by increasing the sintering temperature or using the hydrogen atmosphere instead of high vacuum,which causes by the increase of grain size and the densification.At the optimum sintering conditions,the PIM Fe-50Ni soft magnetic alloy with high properties are obtained,whose relative density,tensile strength,B_(m),H_(c),μ_(m)are 97%,465 MPa,1.52 T,16.62 A·m^(-1),42.5 mH·m^(-1),respectively.

Phase Behaviors in Bi-phase Simulation of Powder Segregation in Metal Injection Molding

Powder segregation induced by mold filling is an important phenomenon that affects the final quality of metal injection molding （MIM）. The prediction of segregation in MIM requires a bi-phase flow model to describe distinctly the flows of metallic powder and polymer binder. Viscous behaviors for the flows of each phase should hence be determined. The coefficient of interaction between the flows of two phases should also be evaluated. However, only viscosity of the mixed feedstock is measurable by capillary tests. Wall sticking is supposed in the traditional model for capillary tests, while the wall slip is important to be taken into account in MIM injection. Objective of the present paper is to introduce the slip effect in bi-phase simulation, and search the suitable way to determine the viscous behaviors for each phase with the consideration of wall slip in capillary tests. Analytical and numerical methods were proposed to realize such a specific purpose. The proposed method is based on the mass conservation between the capillary flows in mono-phase model for the mixed feedstock and in bi-phase model for the flows of two phases. Examples of the bi-phase simulation in MIM were realized with the software developed by research team. The results show evident segregation, which is valuable for improving the mould designs.

Efficacy of Yiqi Fumai (Freeze-Dried Powder) on Ischemic Diastolic Heart Failure

Objective: To evaluate the efficacy of Yiqi Fumai freeze-dry powder (YFP) on ischemic diastolic heart failure. Methods: 100 patients diagnosed with unstable angina accompanying ischemic diastolic heart failure (IDHF) were selected randomly. 52 patients with TCM syndrome of qi-yin deficiency were divided into Chinese and Western combination therapy group. 48 patients have no TCM syndrome of qi-yin deficiency, and were treated with standard western medicine. After treatment, Seattle Angina Questionnaire Evaluation, ECG, conventional and stress echocardiography (SE) index, NT-proBNP were compared between before and after treatment. Results: The differences of PL, TS, DP between before and after treatment by YFP were statistically significant

Comparison of rheological analytic model with numerical simulation in powder injection molding filling process

Mathematical model of filling disk-shaped mold cavity in steady state was studied.And the mathematical model under vibration field was developed from the model in steady state.According to the model of filling disk-shaped mold cavity in steady state,the filling time,the distribution of velocity field and the pressure field were obtained.The analysis results from rheological analytic model were compared with the numerical simulation results using Moldflow software in the powder injection molding filling process.Through the comparison,it is found that it is unreasonable to neglect the influence of temperature when calculated the pressure changing with the time at the cavity gate,while it can be neglected in other situations such as calculating the distribution of the velocity fields.This provides a theoretical reference for the establishment of correct model both in steady state and under vibration force field in the future.

Microstructure and properties of nano-TiN modified Ti(C,N)-based cermets fabricated by powder injection molding and die pressing

Powder injection molding （PIM） and die pressing were employed to fabricate nano-TiN modified Ti（C,N）- based cermets. The shrinkage behavior, microstructure, porosity, and mechanical properties of the samples with and without nano-TiN addition fabricated by PIM and die pressing were analyzed. It is demonstrated that for either PIM or die pressing, the porosities are obviously reduced, the mechanical properties are significantly improved after adding nano-TiN, and the hard particles are refined; the rim phase thickness obviously becomes thinner, and the number of dimples in fracture also increases. Compared the samples fabricated by die pressing, it is difficult for PIM to obtain dense Ti（C,N）-based cermets. Due to the too much existence of pores and isolated carbon, the mechanical properties of the sintered samples by PIM are inferior to those of the sintered ones by die pressing.

A novel binder and binder extraction method for powder injection molding of tungsten cemented carbide

An improved wax based multi component binder and a new debinding method termed high pressure condensed solvent extraction were developed for powder injection molding of tungsten cemented carbide. The results indicate that a critical powder loading of 65% (volume fraction) and an ideal rheological properties were obtained by the feedstock based on the binder. High debinding rate and specimens with high strength were obtained by the debinding method. Moreover, by making high temperature holding time adjustable, it makes the subsequent thermal degradation process more flexible to debinding atmosphere and carbon content of the as debinded specimens controllable. The transverse rupture strength, hardness and density of the as sintered specimens made by an optimized PIM process are 2.48 GPa, HRA90 and 14.72 g/cm 3, respectively. Good shape retention and about 0.02% dimension deviation were achieved.

Numerical Simulation of Powder Injection Molding Filling Process Based on ANSYS

A mathematical model of two-dimensional flows of PIM derived from the momentum, continuity equations and theheat transfer equation is obtained. The formula of calculating the flow conductance and the pressure equation arededuced when the no slip boundary condition is employed at the wall, and the pressure equation is a non-linearelliptic partial differential equation. The flow front locations, distribution of velocities, temperature and pressure aresimulated by the finite element analysis software ANSYS. Simulation results indicate that it is in the final filled partthat defects appear easily. The region in which the defects may occur during the PIM process can be predicted.

Effect of sintering parameters on powder injection molded Ti(C, N)-based cermets

Effect of two-stage sintering parameters such as heating rate, top sintering temperature and holding time, sintering temperature and holding time at the second stage on relative density, transverse rupture strength(TRS) and microstructures of powder injection molded Ti(C, N)-based cermets were investigated, by means of Archimedes’s method, three-point bending test and micrographic analysis. The results show that the optimum sintering cycle for powder injection molded Ti(C, N)-based cermets comprises rapid heating (10℃/min) at low temperatures, slow heating (5℃/min) at intermediate temperatures, holding at the highest sintering temperature (1420℃) for a short time (10min), and holding at the second stage (1360℃) for a longer time (6h) to avoid grain coarsening, and that its TRS reaches 624MPa, and there are little pores in their microstructures.

Sintering Mechanism of Stainless Steel in Powder Injection Molding

Stainless steel samples were made by Powder injection Molding (PIM) process with-400 mesh powder in order to investigate the sintering mechanism in this system and develop the PIM of stainless steels. The process included mixing, injection molding, debin- ding and sintering. Neck growth model was used to analyze the sintering mechanism. The results show that lattice (volume) diffusion is the main mechanism in the sintering process, the products with higher density (>95%) and properties are obtained. At lower temperatures, grain boundary diffusion may play a role in the sintering densification.

YiQiFuMai powder injection attenuates ischemia/reperfusion-induced myocardial apoptosis through AMPK activation

The YiQiFuMai powder injection （ YQFM）, a Traditional Chinese Medicine （TCM） prescription re-de- veloped based on the well-known TCM formula Sheng-maisan, showed a wide range of pharmacological activities in cardiovascular diseases in clinic. However, its role in protection against myocardial ischemia/reperfusion （MI/R） injury has not been elucidated. The present study not only evaluated the eardioprotective effect of YQFM from MI/ R injury but also investigated the potential molecular mechanisms in vivo and in vitro. The mouse model of MI/R injury was induced by a transient vessel occlusion for 30 rain and reperfusion for 24 h. The myocardium infarct size, production of lactate dehydrogenase （LDH）, creatine kinase （CK）, TUNEL staining and easpase-3 activity were measured. AMPKeα and phospho-AMPKα was analyzed by Western blot. We further verified the protective effect and potential molecular mechanisms of YQFM in an in vitro model of simulated ischemia and reperfusion （ SI/ R） in H9c2 cardiomyocytes. Cell viability was determined, and cell apoptosis were measured by Hoechst 33342 staining and Flow cytometry. Mitochondrial membrane potential （△ψFm） was measured, and ATP content was quantified by biolumineseent assay. Expression of apoptosis-related proteins including Caspase-3, Bcl-2, Bax, AMPKα and phospho-AMPKα was analyzed by Western blot. AMPKoL siRNA transfection was also applied to the mechanism elucidation. YQFM significantly reduced myocardium infarct size and the production of LDH, CK in se- rum, and also produced a significant decrease of apoptotic index which was confirmed by TUNEL staining and the changes of caspase-3 activity. In addition, pretreatment with YQFM markedly improved cell viability and decreased LDH release. Moreover, YQFM inhibited H9c2 apoptosis, blocked the expression of easpase-3 and modulated Bcl- 2 and Bax proteins, leading to an increased mitochondrial membrane potential and cellular ATP content. Mechanis- tically, YQFM activated AMPK signaling pathways while pretreatment with AMPK inhibitor compound C and appli- cation of transfection with AMPKα siRNA attenuated the anti-apoptotie effect of YQFM. Our results indicated that YQFM could provide significant cardioproteetion against MI/R injury, and potential mechanisms might to suppres- sion of cardiomyocytes apoptosis at least in part through activating the AMPK signaling pathways.

Silver removal from molten lead through zinc powder injection

A silver removal process was carried out on a Pb-Ag alloy through zinc powder injection of three different sizes （3.55, 44.4 and 734.8μm） with a top submerged lance using nitrogen as carrying gas. The higher silver removal was obtained for the zinc powder size of 44.4μm, while the lowest silver removal efficiency was attained for the smaller particle size. The AgZn phase was detected in the slag for the 44.4 and 734.8μm particle sizes by XRD, which was in agreement with SEM-EDS analysis. Experimental behavior was explained according to the melting and residence time of the injected particles.