Process Optimization And Microstructure Properties Of Titanium-based Foam Metal Prepared By Pore-forming Agent

Titanium foam materials have broad application prospects in orthopedic implant materials,catalyst carriers,and energy absorption and shock absorption.The preparation of titanium foam by powder metallurgy has the advantages of simple operation,low cost,and controllable pore structure.However,the current powder metallurgical preparation of titanium foam is still at the experimental research stage.The influence of its technological parameters on the formability,structure and performance of titanium foam has not been comprehensively studied.The prediction of its porosity is also an urgent problem to be solved.To this end,this study will systematically study the effects of different process parameters and alloy elements Mo on the pore structure and mechanical properties of titanium foam based on the pore-forming agent system,and analyze its influence on the pore structure and microstructure of titanium foam.Experimental verification was carried out to provide a basis for the practicality of the process of titanium foam and the controllable preparation and prediction of porosity.The main content and results of this study are as follows:(1)The experimental results show that the particle size of the pore-forming agent has a great influence on the structure and performance of the titanium foam material.Specifically,the porosity of the titanium foam decreases slightly as the particle size of the pore-forming agent decreases,and the mechanical properties and opening ratio It is the trend of increasing first and then decreasing as the pore size of the pore-forming agent decreases.Comprehensive comparison,when the particle size of the pore-forming agent is 205.46 ?m,the comprehensive performance of the prepared titanium foam is the best,with porosity and open porosity reaching 66.44% and 99.45% respectively.(2)Properly increasing the pressing pressure is conducive to improving the contact between titanium powders and improving the bonding force between titanium powders.Stress release during sintering promotes the sintering process,but excessive pressing pressure is not conducive to the removal process of the pore-forming agent,but it is easy to cause local collapse,and it will also reduce the opening rate of the pores.When pressed under the same conditions When the pressure is 200 MPa,the compressive strength of the titanium foam reaches the highest,that is,26.1 MPa,and the porosity of the pores is also maintained at about 99.05%.(3)The holding time has a more important influence on the sintering quality.Prolonging the holding time of sintering is conducive to a more complete sintering process,and at the same time effectively improves the density of the pore wall,makes the titanium foam have more excellent mechanical properties.When holding for 1 h,its compressive yield strength can reach 23.95 MPa,and then the holding time is further extended,its mechanical properties do not increase much,and it basically tends to be around 24~26.1 MPa.At the same time,if the holding time is extended too much,it is not conducive to obtaining higher porosity and Opening rate,comprehensive consideration that it is more reasonable to sinter for 1 h under the experimental conditions.(4)The amount of pore-forming agent directly determines the pore structure and mechanical properties of titanium foam.As the pore-forming agent increases,the porosity and open porosity of the titanium foam increase,but the porosity is often lower than the amount of pore-forming agent added,and the greater the amount of pore-forming agent,the greater the difference.At the same time,the more the amount of pore-forming agent added,the worse the mechanical properties.When the amount of pore-forming agent reaches 55%,the titanium foam also has an open cell rate of up to 96.14%,and the obtained foamed titanium is already an open-cell structured titanium foam.(5)The addition of Mo element on the one hand increases the density of the cell walls,and at the same time reduces the porosity of the titanium foam,which is beneficial to improve the strength and hardness of the titanium foam.On the other hand,the addition of Mo element greatly promotes the transformation of ?-Ti to ?-Ti,which is beneficial to the improvement of the plasticity of the titanium foam alloy but reduces its strength and hardness.The research results show that under the combined effect of the two,the strength and hardness of the titanium foam alloy increase first and then decrease with the increase of Mo addition.When the amount of Mo element added reaches 12 wt%,its strength and hardness are increased by 44.8% and 59.4% compared with pure titanium foam,respectively,and the elastic modulus decreases with the increase of Mo content.The prediction equation proposed by the research group is not only applicable to pure titanium,but also the titanium-molybdenum foam alloy with 0 wt%~16 wt% Mo addition has high accuracy,which is important for the prediction of porosity of porous materials prepared by powder metallurgy Reference value.