基于微观孔隙演变的Ti-6Al-4V粉末高速压制致密化机理研究  

Study on the Densification Mechanism of Ti-6Al-4V Powder during High Velocity Compaction Based on the Evolution of Microscale Pores

作　　者：周剑 徐宏坤 刘焜[1] ZHOU Jian;XU Hongkun;LIU Kun(School of Mechanical Engineering,Hefei University of Technology,Hefei 230009)

机构地区：[1]合肥工业大学机械工程学院,合肥230009

出　　处：《机械工程学报》2024年第16期180-189,共10页Journal of Mechanical Engineering

基　　金：国家自然科学基金(52375179,51905141);中央高校条件建设经费(JZ2021HGTB0086)资助项目。

摘　　要：采用二维多颗粒有限元法模拟Ti-6Al-4V粉末高速压制成形过程,定量表征颗粒间孔隙的形态特征,详细分析压制过程中多种典型孔隙的形态和面积填充变化规律,从微观孔隙演变的角度研究粉末致密化机理。模拟结果发现,当宏观压制压力低于临界压力(约为1500 MPa),颗粒主要通过重排和塑性变形来填充孔隙,密度-压力曲线斜率较大,致密化较容易;超过临界压力后,曲线斜率逐渐减小,致密化越来越困难。微观上,在颗粒重排和塑性变形阶段,颗粒体系中存在大量面积比较大且压制角度较小的四边形孔隙,以及拱形结构容易被破坏的五边形孔隙。这些孔隙在压制过程中会转化为其他多边形孔隙,填充速率较快且具有较高的填充率,在粉末致密化的前中期起主要作用。高于临界压力值之后,大多数四边形和五边形孔隙均转化为三边形孔隙,此外还存在少量具有特殊堆积结构的多边形孔隙,这些难以填充的孔隙导致后期粉末致密化较为困难。研究结果建立不同类型孔隙的形态演变与粉末致密化难易程度之间的定性关联,为构建压制本构方程和优化成形质量提供理论指导。The high velocity compaction process of Ti-6Al-4V powder is simulated by using two-dimensional multi-particle finite element method.The morphological features of pores among particles are quantitatively characterized.The change laws regarding the morphology and area filling of various typical pores during the compaction process are analyzed in detail.The powder densification mechanism is studied from the aspect of the evolution of microscale pores.The simulation results show that when the compaction pressure is lower than a critical value(about 1500 MPa),pores are mainly filled by particle rearrangement and plastic deformation,so that the slope of the density-pressure curve is steep,and the green powder assembly is easily densified.Above that critical pressure,the slope of the density-pressure curve gradually decreases,and powder densification becomes difficult.Microscopically,at the stage of particle rearrangement and plastic deformation,there are many quadrilateral pores with large area-ratios and small compression angles,as well as pentagon pores with arched structures that are easily damaged.Since these pores can be transformed into other polygonal pores during compaction,they have high filling ratios,and play a major role in the early and middle densification stages.When the compaction pressure is higher than the critical value,most of the quadrilateral and pentagonal pores has been transformed into triangular shapes.Additionally,there are a small number of polygonal pores with special packing structure.These pores that are hard to be filled lead to the difficult densification in the later stage.The research results establish a qualitative relationship between the morphological evolution of different types of pores and the difficulty of powder densification,which would provide theoretical guidance for both the construction of the compaction constitutive equation and the optimization of the forming quality.

关 键 词：TI-6AL-4V 高速压制 粉末致密化 多颗粒有限元法 孔隙形态 

分 类 号：TF121[冶金工程—粉末冶金]