Change of Microstructure for Casting TC21 Alloys after Thermohydrogen Treatment

Thermohydrogen treatment which uses hydrogen as a temporary alloying element can fine microstructure of titanium alloy and improve its properties. It has importance meaning on casting titanium alloy. The behavior of hydrogen absorption on microstructure of TC21 alloy as cast was studied. The results show that the β-phase amount increase and a few hydrides precipitate after charging hydrogen. When hydrogen is desorbed, the resulting structure is fine and homogeneous,and the hardness change a lot with it. The mechanism of fining microstructure was analyzed.