双重退火对激光增材制造TC18钛合金组织和性能的影响

Effects of Double Annealing on Microstructure and Properties of TC18 Titanium Alloy by Laser Additive Manufacturing

利用拉伸试验机、扫描电镜和金相显微镜等手段,研究了双重退火工艺(890℃×1 h/FC+750℃×2 h/AC,570℃×4 h/AC)对激光增材沉积和修复两种状态的TC18钛合金的组织和力学性能的影响,并与原始锻件TC18钛合金进行比较。结果表明,激光增材修复试样微观组织为典型的类铸态组织,主要由层状β晶粒组成。激光增材修复试样经双重退火后为魏氏组织,原始β晶界仍清晰可见,晶内分布着交错的(α+β)集束。经双重退火后,激光增材沉积试样强度低于锻件,塑性高于锻件,激光增材修复试样的性能介于两者之间,其冲击性能比锻件的冲击性能高约60%。激光增材沉积、激光增材修复两种状态经退火热处理后力学性能都能达到TC18锻件规定值。

The effects of double annealing processes(890℃×1 h/FC+750℃×2 h/AC,570℃×4 h/AC)on the microstructure and mechanical properties of TC18 titanium alloy by laser additive deposition and repair were investigated by tensile testing machine,scanning electron microscope and metallographic microscope,and compared with original forging TC18 titanium alloy.The results indicate that the microstructure of the repaired specimen is characterized by as-cast microstructure,which is mainly composed of lamellarβ-grains,and presents the Widmannian structure after double annealing,where the originalβgrain boundary is still clearly visible,and the interlaced(α+β)clusters are distributed within the grains.After double annealing,the strength of the deposited specimen is lower than that of the original forgings,while the plasticity is the higher.The properties of the repaired specimen are between the two.The impact properties of the repaired specimen are about 60%higher than that of the forgings.After annealing,the mechanical properties of both specimens can reach the prescribed value of TC18 forgings.