Al元素对一种增材制造镍基高温合金显微组织和拉伸行为的影响

Effect of Al on Microstructure and Tensile Behavior of an Additive Manufacturing Nickel-Based Superalloy

为了明晰Al元素在增材制造镍基高温合金过程中对组织和性能的影响,通过激光金属沉积方法制备了不同Al含量的样品,分析了其显微组织以及拉伸行为的影响.结果表明:随着w(Al)增大(3%~5%),γ/γ′共晶、碳化物等析出相以及组织中裂纹等缺陷逐渐增加并在w(Al)=7%时达到最大,由高熔点碳化物钉扎在晶界和低熔点共晶重熔分别导致的凝固裂纹和液化裂纹大量形成.合金强度随着Al元素的增加先增后降,w(Al)=4%时达到最高,归因于γ′相的尺寸和立方度不断增加,阻碍位错的运动.而w(Al)=5%时性能下降归因于已有热裂纹、碳化物以及共晶含量的增加.

To clarify the effect of Al on the microstructure and properties of nickel base superalloy produced by additive manufacturing,the effects of Al on the microstructure,tensile properties and deformation mechanism were analyzed via the Ni based superalloys with different Al contents prepared by laser metal deposition.The experimental results show that with the improvement of Al content(3%to 5%),theγ/γ′eutectic,carbides and cracks in microstructure increase a few.When the Al content reaches 7%,the quantity ofγ/γ′eutectic and carbides increase prominently.A large number of solidification cracks and liquefaction cracks,which are formed due to the pinning of high melting point carbides at grain boundaries and the remelting of low melting point eutectic,respectively,can be observed.The strength of the alloy increases first and then decreases with the increase of Al element,and the alloy with 4%Al has the highest strength.It is due to the increasing size and cubic ofγ′phase that hinders the movement of dislocations effectively.The decrease of strength and plasticity of the alloy with 5%Al is attributed to the increase of existed hot cracks,carbides and eutectic.