TA2薄钛板搅拌摩擦焊接头的显微组织与力学性能分析

Microstructure and Mechanical Properties of Friction Stir Welded Joint of TA2 Thin Titanium Plate

摘要:

为了探究搅拌头转速、焊接速度、轴向压力等工艺参数对薄钛材焊接质量的影响规律，采用搅拌摩擦焊技术对厚度为3 mm的TA2方形薄钛板进行焊接，并对搅拌摩擦焊件接头的显微组织及力学性能进行了研究。结果表明：当搅拌摩擦焊工艺参数为焊接速度60 mm?min^-1、转速300 r?min^-1、焊头倾角1°—3°、焊接压力20—25 kN和氩气流量16 L?min^-1时，焊缝区域结构完好，未出现小孔、夹杂物和裂纹等常见的焊接缺陷。通过对焊接接头显微组织分析发现，该区域的显微组织主要为2.5—32 μm细小等轴晶，晶粒尺寸沿焊缝中心呈现倒V型对称分布，并从焊缝中心向母材方向逐渐增大。表明，焊接过程中温度和应力的分布对晶粒的生长有显著影响。焊缝区域的显微硬度为131.9—138.1HV，随离焊缝中心距离的增大而降低，焊缝区域的平均晶粒尺寸和平均显微硬度分别是12.8 μm和135.4 HV，均显著优于母材区域的57 μm和125.1 HV。相较于母材，焊缝区域的晶粒尺寸和硬度表现出显著的优越性，表明焊接过程有效细化了晶粒及提高了材料的局部硬度。导电率方面，焊缝区域为3.65%IACS，低于母材区域的3.82%IACS。通过残余应力测试发现，焊缝中心区域的最大残余应力为420 MPa（横向）和180 MPa（纵向），在距焊缝中心15—20 mm处出现压应力。拉伸测试结果显示，搅拌摩擦焊件及母材的抗拉强度分别为415和297 MPa、屈服强度为325和258 MPa、延伸率为32%和62%，焊接接头的强度得到提高，但塑性性能有所下降，这是因焊接过程中产生的显微组织细化和残余应力所致。通过研究确定了搅拌摩擦焊焊接薄钛材最优的工艺参数组合，提高了焊接效率和质量的稳定性。

Abstract:

IN order to explore the influence laws of process parameters such as stir - head rotation speed， welding speed， and axial pressure on the welding quality of friction stir welding of thin titanium materials. The TA2 square thin titanium plate with a thickness of 3 mm was welded friction stir welding， and the microstructure and mechanical properties of the weld joint were analyzed. The findings indicate that the weld area is free from defects such as pores， inclusions and cracks，The metallographic microstructure of the weld area is mainly composed of fine equiaxed grains ranging from 2.5 to 32 μm， with grain growth occurring sequentially from the center of the weld to the base metal，The grain size exhibits a symmetrical inverted "V" distribution along the weld center. The microhardness in the weld area ranges from 131.9 to 138.1 HV， decreasing progressively from the weld center to the base metal. The average grain size and microhardness of the weld area were 12.8 μm and 135.4 HV， respectively， compared to 57 μm and 125.1 HV in the base metal area， indicating that the weld area’s grain size is 44.2 μm smaller and its microhardness is 10.3 HV higher than that of the base metal. The average conductivity of the weld region and base metal region was measured at 3.65%IACS and 3.82%IACS， respectively， that the weld region has a conductivity 0.17% lower than that of the base metal. Residual stress measurements using the MTS3000 blind hole method revealed that the central weld exhibited the highest residual stress， with transverse and longitudinal stresses of 420 MPa and 180 MPa respectively，Compressive stress was observed 15—20 mm from the weld center .Tensile test indicated that the the friction stir weldment achived a tensile strength of 415 MPa， yield strength of 325 MPa and elongation of 32%， compared to 297 MPa， 258 MPa， and 62% for the base metal Through this research， the optimal combination of process parameters for friction stir welding of thin titanium materials was determined， which improved the welding efficiency and quality stability.