Effects of solution treatment and aging on microstructure and properties of 21-4NWNb alloy were investigated by means of XSL-4-12 box resistance furnace,ZEISS metallographic microscope,ZEISS Merlin Compact field emission scanning electron microscope,KB 30S automatic hardness test system,CMT5305 electronic universal testing machine,and JEM-2100F field emission transmission electron microscope.The results show that solution treatment can effectively improve the grain structure of the alloys.When the solution treatment temperature is in the range of 1150-1200 ℃,a large amount of carbides in the alloy almost completely dissolve into the austenite matrix,and the Nb(C,N)phases cannot completely dissolve even at the solution treatment temperature of 1200 ℃.The hardness of the alloy decreases with the increase of solution treatment temperature.The grain size of the alloy remains basically unchanged after different aging treatments.At higher aging temperatures(650-800 ℃),hardness of the alloy shows a trend of first increasing and then decreasing with the increase of aging temperature.After solution treatment at 1150 ℃ for0.5 h and then aging at 750 ℃ for 4 h,the tensile strength of the 21-4NWNb alloy reaches 1042 MPa,and there is a(110)WN//(220)γ relationship between the WN precipitate phases in the alloy and the Fe matrix.
21-4NWNb alloysolution treatment and agingmicrostructureproperties
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