Microstructure Adjustments And Performance Optimization Of Ti6A14V Alloy Processed By Selective Laser Melting

Selective laser melting(SLM),as one of the most typically additive manufacturing(AM)technology,has been widely used in biological medical field.But there is little research about relationship between processing parameter and performance of parts fabricated by SLM.Therefore,by changing the process parameters during laser melting Ti6Al4 V,the microstructure of parts in biological medical field can be adjusted;as a result,controllable performance of Ti6Al4 V parts elaborated by SLM can be achieved.The main contents of this thesis are as follows:(1)Mechanical properties.a.Tensile property.As the scanning speed increases,the tensile strength and yield strength of parts slowly rise,and then decline sharply.With the increasing of laser power,the tensile strength and yield strength of parts first rise,and then decrease.As the scanning speed and laser power increase,the elongation of parts first rises and then declines sharply.Increasing scanning speed or decreaseing laser power makes the grain refine.As a result,the tensile strength and yield strength of parts increase.However,the elongation of parts declines.To low scanning speed or too high laser power induces the formation of holes,which reduces the tensile properties of the parts.Hence,the results show that by changing the scanning speed and laser power,grain size and defect can be adjusted;as a result,controllable tensile property of Ti6Al4 V parts elaborated by SLM can be achieved.b.With the scanning speed and laser power increaseing,the hardness of parts first rises,follows by a decline.Relative lower scanning speed or relative higher laser power leads to the distribution of the acicular martensite haphazard.Relative higher scanning speed or relative lower laser power causes the area of the acicular martensite to decrease.Hence,by changing the scanning speed and laser power,grain size,defect and diatribution of acicular martensite can be controlled;as a result,controllable hardness of Ti6Al4 V parts elaborated by SLM can be achieved.c.With the scanning speed and laser power increasing,the surface roughness of parts shows a rise first,and then decline.Lower scanning speed or higher laser power means higher laser power energy density.Higher laser power energy density leads to large overlap rate of the fuse,which causes over-melten.Lower laser power energy density(the scanning speed is too high or the laser power is too low),makes small overlap rate of the fuse,which presents a worm.Hence,by changing the scanning speed and laser power,the width and quality of the fusing can be adjusted;as a result,controllable surface roughness of Ti6Al4 V parts elaborated by SLM can be achieved.d.With the scanning speed and laser power increasing,the fatigue life of parts first rises,then declines.Because the scanning speed and laser power affact defect,distribution of acicular martensite and surface roughness,controllable fatigue life of Ti6Al4 V parts elaborated by SLM can be achieved.(2)Corrosion resistance.With the scanning speed and laser power increasing,the corrosion resistance of parts first rises,then declines.Increaseing the scanning speed or decreaseing the laser power makes refined grain obtaine,which leads to the corrosion of the crystal inhence and the corrosion resistance decrease.However,too highs canning speed or too low laser power induces holes appear,which can increase the corrosion rate and reduce the corrosion resistance of the parts.Hence,by changing the scanning speed and laser power,grain size and defect can be adjusted;as a result,the corrosion resistance of Ti6Al4 V parts elaborated by SLM can be controlled.(3)Biological properties.With the increasing of scanning speed,the cell proliferation rate increases linearly and then decreases sharply.Compared to scanning speed,laser power has less influence on biological properties.The scanning speed increasing or the laser power decreaseing can induce refined grain,inhencement of the corrosion of the crystal and decreases of corrosion resistance.The precipitation of the toxic ions increases,and the biological property decreases.Too high scanning speed or too low laser power makes the formation of holes,which can increase the corrosion rate and reduce the biological property of the parts.Hence,grain size and defect can be adjusted by changing the scanning speed and laser power;as a result,controllable biological properties of Ti6Al4 V parts elaborated by SLM can be achieved.