The Influence Of Super Gravity On The Microstructures And Properties Of Al_97.5Ni_2.5 Alloy

With the development of aviation,automobiles,high-speed rail and other modern industry,a higher requirement is put forward for the super light structure material.As an important kind of super light structure material,most interest was put on aluminum alloy.The grain size of the conventional aluminum alloy is tens of microns,and if it can be refined to micron or sub micron,that will make great progress in the development of aluminum alloy.Super gravity field,a special physical field,is rarely studied in the field of solidified metal materials,but there is some data which still indicates that super gravity field is beneficial to grain refinement.In this paper,the effects of super gravity field and Cr content on the microstructures and properties of the Al_97.5Ni_2.5 alloy were studied.Compared with Al_97.5Ni_2.5 alloy solidified under normal gravity,when the alloy was solidified under super gravity field,the average grain size of primary phase α（Al）decreased from 28.61μm to15.43μm,the average diameter of rod-like Al3 Ni eutectic phase and eutectic spacing λ reduced from 330 nm and 1050 nm to 280 nm and 650 nm respectively,the volume fraction of rod-like Al3 Ni phase increased from 10.8% to 14.2%.Along the direction of gravity field,the microstructure distribution was substantially uniform;along the direction perpendicular to the super gravity field,microstructures delaminated.When the super gravity field increased from 1g to 2000 g,the grain was refined obviously,and the hardness increased evidently.When the super gravity field increased from 2000 g to 11000 g,the trend of grain refinement and the increase of hardness became slow.When G=11000g,the primary phase α（Al）,the average diameter of rod-like Al3 Ni eutectic phase and eutectic spacing λ were refined the most,reached 9.13μm、116nm and 420 nm respectively.When the super gravity field increased from 1g to 11000 g,the hardness increased from HV 44.24 to HV 58.79.The hardness increased by 32%.The mechanism of grain refinement under super gravity field was discussed.The addition of Cr can refine the grain and improve the hardness of Al_97.5Ni_2.5 alloy apparently.When x=1,the primary phase α（Al）was refined the most,the average grain size is 1.23μm;when x=1.5,the average diameter of rod-like Al3 Ni eutectic phase and eutectic spacing λ was refined more,reached 53 nm and 170 nm respectively.When x=2,the average hardness of the alloy has a maximum value of 83.69.Compared with Al_97.5Ni_2.5 alloy which solidified under 11000 g super gravity field,the hardness increased by 40%.