Influence of Hydrogen Content on Cold Heading of TC21 Titanium Alloy Hexagon Bolt and Microstructure Microhardness
In this paper,a hex head bolt of hydrogen TC21 titanium alloy with different hydrogen content is cold-headed by a material testing machine.The microstructure and hardness of the hex head bolt are studied by metallographic microscope an micro-Vickers hardness tester.It is found that when the hydrogen content is 0.79wt.％,cracks only occurred on the outer surface of the head of the hexagon head bolt.With the hydrogen content increasing from 0.79wt.％to 0.91wt.％,the cracks of hexagon head bolts in cold heading process increased gradually.At hydrogen contents of 0.79 wt.％,0.82 wt.％,and 0.91 wt.％,the microstructural morphology of cold-headed hexagon bolts made from TC21 titanium alloy with varying hydrogen contents appeared similar.The content of β phase was higher,while the content of α phase was lower.With the increase of hydrogen content,β grain boundaries gradually became indistinct or even disappeared,and the dislocation density decreased progressively.As the hydrogen content increased,microhardnesses across all regions of the cold-headed TC21 titanium alloy hexagon bolts increased gradually.When the hydrogen content is the same,there is a similar pattern of microhardness variation across the four regions of the cold-headed TC21 titanium alloy hexagon bolts.
万方数据
维普
