材料期刊网

尺寸为210 mm×210 mm的TB6钛合金方形棒材经固溶加时效处理后,心部形成过热区.研究了过热区对TB6钛合金棒材组织与性能的影响.结果显示,距棒材表面深度为60 mm以内的区域为正常的球状等轴组织,深度超过65 mm的心部过热区为针状网篮组织.过热区的形成主要是由于心部区域在固溶处理时的冷却速度低于临界冷却速度,没有生成亚稳β相,而直接生成α+β相造成的.棒材横截面上过热区面积占比约18.4%,相比正常区域,其抗拉强度最大降低22.9%,屈服强度最大降低28.5%,布氏硬度降低4.2%,但是具有较好的塑性、较高的平面应变断裂韧度与较强的抗疲劳裂纹扩展能力.过热区的存在增大了棒材横截面组织与性能的不均匀性,降低了TB6钛合金棒材及后续所制锻件的安全系数,必须予以避免.

Over-heated zone appeared in the heart area of TB6 titanium alloy bar with the size of 210 mm × 210 mm after solution and aging treatment. This paper studied the influence of the over-heated zone on the microstructure and properties of the TB6 titanium alloy bar. The results show that the microstructure of the cross-sectional area is normal globular and equiaxed alpha phase when the depth is within 60 mm and acicular lamellar structure when the depth is more than 65 mm. During solution treatment large-sized bar could not get critical cooling rate in its heart area where alpha+ beta phase instead of metastable beta phase is generated which makes over-heated zone appeared. The over-heated zone of TB6 titanium alloy bar,accounted for about 18. 4% of cross-sectional area,has its tensile strength decreased at most 22. 9%,yield strength decreased at most 28. 5%,HBW decreased 4. 2% than normal zone;but it has better plastic toughness and higher fatigue crack expansion capability. The existence of the overheated zone decreases the uniformity of the cross-sectional microstructures and properties which makes the mechanical properties of the TB6 alloy bar and the subsequent forgings fail to meet the requirements of technical standards and must be prohibited.