热处理对TC18钛合金大块富α相区的影响

对含亮斑缺陷的TC18钛合金棒材试样通过EDS能谱及光学显微镜分析缺陷的相组成、尺寸及组织形貌,并利用显微硬度仪进一步分析热处理对缺陷区及正常区显微硬度的影响。EDS能谱及金相分析表明,亮斑为α相富集区,并有一定宽度的过渡区。经1 150℃×2 h/WQ均匀化热处理后,亮斑面积明显减小,亮斑区与过渡区的边界被弱化。进一步经840℃×1 h/FC至720℃×1 h/AC+590℃×4 h/AC常规热处理后,过渡区组织与正常区组织无明显差别,亮斑区α相含量比正常区域稍有增加,组织形貌均为网篮组织。硬度分析表明,1 150℃β相区固溶+常规固溶加时效处理后缺陷区与正常区的硬度差别很小,这表明通过β相区高温固溶预处理可以改善TC18钛合金中的微观偏析。

The Effect of Heat Treatment on Large Dimension of α-rich Region of TC18 Titanium Alloy

The bright spot of received TC18 titanium alloy bar was analyzed by energy dispersive spectrometer（ EDS） and optical microscope（ OM）to identify the phase composition,dimension and microstructure. Then the microhard-ness of the alloy in different region was analyzed by Vickers hardness tester. The EDS and OM analysis indicated that the bright spot wasα-rich region,enclosed by transition region. The 1 150 ℃ × 2 h/WQ solution heat treatment could effectively reduce the size of α-region and fuzz the boundary of it. The sample was then conventionally processed by 840 ℃ × 1 h/FC to 720 ℃ × 1 h/AC ＋590 ℃ × 4 h/AC. After then,the microstructure of transition region and normal region was nearly the same,and distinction ofαphase percent between theα-rich region and the normal region was only a little,all of the microstructure in different region was basketwave. Further microhardness analysis verified that there was nearly no difference between α-region and normal region. These results show that pre-heat treatment at 1 150 ℃ can effectively improve the microsegregation of TC18 titanium alloy.