固溶时效处理对21-4NWNb合金组织与性能的影响

Effect of solution treatment and aging on microstructure and properties of 21-4NWNb alloy

利用XSL-4-12箱式电阻炉、ZEISS金相显微镜、ZEISS Merlin CoMpact场发射扫描电镜、KB 30S全自动硬度测量系统、CMT5305电子万能试验机及JEM-2100F场发射透射电镜,研究了固溶-时效处理对21-4NWNb合金组织与性能的影响。结果表明:固溶处理能有效改善合金的晶粒组织,当固溶温度在1150~1200℃时,合金内大量的碳化物几乎都已经固溶到奥氏体基体中,Nb(C,N)相即使在固溶温度为1200℃时也无法完全溶解;合金的硬度随固溶温度的升高呈下降趋势,不同工艺时效处理后合金的晶粒尺寸基本不变;在较高时效温度(650~800℃)下,合金硬度随着时效温度的升高呈先上升后下降的趋势。1150℃×0.5 h固溶+750℃×4 h时效后,21-4NWNb合金的抗拉强度达到了1042 MPa,且合金内部存在与Fe基体保持着(110)WN//(220)γ位向关系的WN析出相。

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℃for 0.5 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)γrelationship between the WN precipitate phases in the alloy and the Fe matrix.