含磷IN718合金高应变速率下超塑性变形行为的试验研究

Superplastic Deformation Investigation of Phosphorus Added IN718 Alloy at Higher Strain Rates

研究了含0.022%磷的IN718合金在高应变速率（5×10-2~4×10-1s-1）下的超塑性变形行为及机制。在试验条件下,合金的拉伸延伸率均超过100%,具有超塑性变形能力。随应变速率升高,延伸率降低至139%,试样颈缩严重,呈针尖状＂点式＂断口,断口附近晶粒组织明显细化,并存在与拉伸方向平行的纵向裂纹,碳化物对塑性变形的阻碍作用是裂纹形成的重要原因。当变形速率为5×10-2~10-1s-1时,IN718合金的超塑性变形机制为动态再结晶;当变形速率为2×10-1~4×10-1s-1时,动态再结晶仍为主要变形机制,但孪晶开始形成并起重要的协调变形作用。

The superplastic deformation behavior and mechanism of IN718 alloy with 0.022% phosphorus addition has been investigated at higher strain rates. The elongations of all tensile specimens within the test conditions are all higher than 100%, exhibiting the superplastic deformation ability. The elongation is decreased to 139% with the increasing strain rates. The area of the fracture surface appears like a needle point, the grain structure is noticeably refined and cracks parallel to the loading direction near the fracture surface are induced by the carbides which could not deform coordinately with the matrix around themselves. The alloy deformation mechanism is dynamic recrystallization at the strain rate 5×10-2-10-1s, while twins are formed and play an important role of coordinating the deformation when the strain rate is in the scope of2×10-1-4×10-1s-1.