以热机械处理获得的超细晶1.6%C超高碳钢为研究对象,借助电致超塑性压缩试验研究了电场强度和初始应变速率对超高碳钢超塑性的影响,并探讨了其与40Cr钢电致超塑性焊接的可行性.实验结果表明,在压缩温度780℃、初始应变速率(0.5-5.0)×10-4 s-1,试样接正极环状电极接负极条件下,超高碳钢的应力应变曲线呈现出明显的超塑性压缩流变特征,其应变速率敏感性指数为0.46;当电场强度为3 kV/cm时,其超塑稳态流变应力降低10%以上.在焊接温度780℃、初始应变速率1.5×10-4 s-1、预压应力56.6MPa、电场强度3 kV/cm条件下,超高碳钢与40Cr钢实现了电致超塑性焊接,其接头拉伸强度达到533 MPa,比不加电场时增加15%.
1.6% C ultrahigh carbon steel (UHCS) with ultrafine structure developed by thermo-mechanical treatment was selected.The effects of electric field intensity and initial strain rate on the superplasticity of the UHCS were studied by means of electro-superplastic compression tests,and the possibility electro-superplastic welding of UHCS to 40Cr steel was discussed.The stress-strain curves of UHCSs show obvious compressive superplastic flow characteristic at the temperature of 780 ℃ and the initial strain rate of (0.5-5.0)×10-4 s-1 in the manner of the specimen connected to positive terminal and the ring electrode connected to negative terminal,the strain rate sensitivity is 0.46.At the electric field intensity of 3 kV/cm,the steady superplastic flow stress of UHCS decreases more than 10%.The electro-superplastic welding of UHCS to 40Cr steel can be carried out under the conditions of a pre-pressed stress of 56.6 MPa,an initial strain rate of 1.5×10-4 s-1,a welding temperature of 780 ℃ and an electric field intensity of 3 kV/cm.The joint strength is up to 533 MPa,which increases more than 15% as contrasted with that obtained without electric field.
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