轧制工艺对源于EB熔铸TC4板材组织和性能的影响

Effect of rolling process on microstructure and properties of TC4 plates derived from electron beam casting

用两种工艺对电子束冷床炉熔铸的TC4钛合金扁锭直接轧制,分3个轧程制备8 mm厚度板材,用光学显微镜、扫描电镜和Image-ProPlus图像分析软件研究板材的组织演变,通过测试力学性能和观察断口研究轧制工艺对板材力学性能的影响。结果表明:第1轧程加热温度为965℃(工艺A),半成品板材表面出现严重的宏观裂纹,而第1轧程加热温度为1065℃(工艺B),半成品板材表面质量显著改善,得到片层α平均厚度为0.5μm的魏氏组织;两种工艺第2轧程变形后初生α细化程度相当,表明片层α厚度减薄有利于组织的破碎;第3轧程后,工艺A获得板材TD方向的抗拉强度为939 MPa、屈服强度为850 MPa、伸长率为12.5%,工艺B获得板材TD方向的抗拉强度为926 MPa、屈服强度为884 MPa、伸长率为16.5%,均满足室温力学性能要求,但工艺B制备的板材屈服强度较高且断后伸长率未表现出各向异性。因此,推荐采用工艺B,即第1轧程加热温度为1065℃、第2轧程为945℃、第3轧程为920℃和单次变形量约为60%的工艺实施铸坯直接轧制TC4钛合金板材。

The TC4 titanium alloy ingot cast by electron beam cold hearth melting furnace were rolled by two kinds processes,and plates with a thickness of 8 mm were prepared by three rolling times.Optical microscope,scanning electron microscope and Image-ProPlus image analysis software were used to study microstructure evolution of the plate.The influence of rolling process on the mechanical properties of plate was studied by testing the mechanical properties and observing fracture.The results show that when heating temperature of the first rolling is 965℃(process A),and serious macro cracks appear on the surface of the semi-finished plate,while heating temperature of the first rolling is 1065℃(process B),surface quality of the semi-finished plate significantly improve,and a widmanstatten structure with an average thickness of lamellaαof 0.5μm is obtained.The degree of primaryαrefinement after the second rolling of the two processes is equivalent,indicating that thinning of lamellaαthickness is beneficial to breakage of microstructure.After the deformation of the third rolling,the tensile strength in TD direction of the plate obtained by the process A is 939 MPa,the yield strength is 850 MPa and the elongation is 12.5%,and the tensile strength in TD direction of the plate obtained by the process B is 926 MPa,the yield strength is 884 MPa and the elongation is 16.5%,both of which meet the requirements of mechanical properties of TC4 titanium alloy plates at room temperature,but the plate prepared by process B has higher yield strength and no anisotropy in elongation.Therefore,process B is recommended,that is,the heating temperature of the first rolling is 1065℃,the heating temperature of the second rolling is945℃,the third rolling is 920℃and the single deformation is about 60%,TC4 titanium alloy plates is directly rowed.