研究并分析TC21钛合金扩散连接接头的微观组织、界面结合质量、显微硬度和压缩变形率随连接工艺参数的变化规律.结果表明:连接温度的提高及连接时间的延长分别导致扩散系数的增大和扩散程度的增加,同时变形能力增大,因而界面焊合率提高,但接头变形率增大;在880 ℃的连接温度下,只要连接时间介于15~30 min,界面焊合率就能达到100%,而接头变形率可控制在10%以内.接头显微硬度随连接温度的升高而明显提高,但随连接时间的变化存在峰值.对接头微观组织特征的分析表明:连接温度越高,两相长大速率越快,两相尺寸增大;但当连接温度达到980 ℃时,被焊母材处于β单相区,较快的冷却速度下α相不能完全析出,接头微观组织因此变为层片状的两相组织.随着连接时间的延长,两相尺寸先增大,当连接时间延长到90 min后,高温下由α相转变而来的β相增多并被保留下来,割裂了原有的两相,使两相尺寸减小.正是接头微观组织的这种变化特征,决定了显微硬度的变化规律.
The diffusion bonding of TC21 titanium alloy with initial grain size of 2 μm was performed at 780-980 oC for 5-90 min. The microstructure, bonding quality, microhardness and deformation ratio of the joints were analyzed. It is found that the interface bonding ratio can achieve 100% and the deformation ratio can be controlled within 10% when diffusion bonding is performed at 880 oC for 15-30 min. The microhardness of the joints increases with increasing of bonding temperature, but it shows a peak value as the bonding time is prolonged. When the joint is bonded at 880-930 oC, fully equiaxed structures are observed, and with increasing of bonding temperature, the sizes of α and β phases are increased; but when bonding temperature is up to 980 ℃, fully lamellar struc-tures are obtained. When the joint is bonded at 880 oC for 5-60 min, the size of α and β phases increases with prolonging of bonding time. However, when the bonding time is prolonged to 90 min, the sizes of α and β phases decrease slightly.
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