Research On High Densification And Numerical Simulation Of Metal Powder Compaction Processes

The powder metallurgic parts have wildy been applied in mechanics, automobiles, electronics, automation and so on, it is has wide market prospect in industry. But the inherent pores have an important influence on the properties of PM parts, and also add difficulties to high precise forming. The relative density of PM parts are generally lower than 90% by conventional powder compaction processes, therefore how to get high density and high properties of powder metallurgic parts becomes to the current development and research focus of powder metallurgic industry. Finite element simulation technology is a rapid, effective and detailed method to analyze densification of powder compaction process. In this article, high densification principle of powders compaction processes, relationship between mechanical properties and density, and finite element simulation of powder compaction are studied:(1) The key influences on densification of warm compaction process: powder and die temperature, pressing pressure, are analyzed. And the resistance heating method is designed for warm compaction process and the effectiveness of this method is verified. Research on fluidity of Fe-based alloy powder at different temperatures is done, and the controlling temperature range of powder is obtained for warm compaction process. The influence of powder and die temperature variation under different pressing pressures are analyzed on densification of powder compaction. The optimism of process parameters for warm compaction process is concluded. And the densification mechanism of warm compaction process is studied.(2) The application of electromagnetic induction heating technology in warm compaction process is researched. Electromagnetic induction heating system is designed for warm compaction process, and effectiveness of this system is verified. The experimental results of this system show that electromagnetic induction heating technology can rapidly, accurately and effectively control die temperature, and this heating technology is successfully applied in warm compaction process. Experimental results of compaction process show that electromagnetic induction heating system for warm compaction process can get high density of PM parts, and there is no influence of magnetism of powders and dies on densification of powder.(3) The dropping hammer and split Hopkinson bar test are applied for researching on high velocity compaction process. The deformation of two powder materials, Fe-based alloy powder (Distaloy4600A) and Pure Ti powder (Ti-Dupont), are analyzed for high velocity compaction process. The data collecting mode (SCXI-1520 and SCXI-1314) and data collecting software (Labview) made by National Instruments, In.. are applied for studying dies deformation during high velocity compaction process. The data collecting program is designed for this research in this article. For dropping hammer test method, height and weight of hammer, type and weight of powder and different compacting processes, and so on are researched on densification of powder. For split Hopkinson bar test, the influence of different impacting pressure on densification of powder is analyzed. The densification mechanism of powder is studied for these two methods, and uniformity of density distribution is researched for high velocity compaction process. The experimental results show that high density and good uniformity of density distribution can be obtained for PM parts by dropping hammer process, it is limited to improve density of PM parts for several hitting on powder.. And the experimental results also show that stress wave has no effect on densification of powder for split Hopkinson bar test.(4) The relationship between density and mechanical properties of Fe-based alloy powder metallurgic parts are studied, and the relationship between relative density and Young's modulus is generalized, this mode can offer basic material information for powder compaction by finite element simulation. And the frictional behavior of powder compaction is also researched in this article, and the results express that at the initial stage of powder compaction, with the increasing of PM parts density, the friction parameter increases, and when the frictional parameter reaches some value, it will almost linearly decrease. The relationship between relative density and Vickers hardness is analyzed for Fe-based alloy powder, Pure Ti powder, and Al6061 powder. And the relationship between relative density and Vickers hardness are established, this mode can be easily applied for analyzing the distribution of local density of powder metallurgic parts, especially complex PM parts.(5) Based on the research of powde densification for warm compaction process, the couple thermal-mechanical finite element mode is obtained for simulating the warm compaction process. The influence of temperature and frictional behavior on the deformation and properties of green are considered. And the updated Lagrangian Method is applied for the simulation of warm compaction process. In this article the influence of different compaction processes on densification of warm compaction are researched, including different heating methods, different frictional status, different ratio of height and diameter, different compaction methods, favorable of conversion of friction, and three-axial compaction method. The deformation of powder particles are analyzed, variation of density and stress distribution are obtained for warm compaction process.