拉晶速率对DZ125合金微观组织及蠕变性能的影响

Effect of Withdrawal Rate on Microstructure and Creep Properties of DZ125 Alloy

在不同的拉晶速率下制备定向凝固DZ125合金,利用扫描电镜对合金试样微观组织进行观察,并测定合金试样在980℃/235 MPa条件下的蠕变曲线,研究了拉晶速率对DZ125合金显微组织及力学性能的影响。研究结果表明:当凝固拉晶速率为1 mm/min时,合金中MC型碳化物为片状结构,尺寸较大,随拉晶速率增加,碳化物尺寸降低,由长条薄片状转变为块状。合金中的γ′相尺寸随拉晶速率的增大略有减小。测定出拉晶速率为1 mm/min、3 mm/min和5 mm/min合金在980℃/235 MPa条件下的蠕变曲线表明,低拉晶速率合金具有较小的初始伸长量,稳态蠕变阶段应变速率较大。试验条件下,高拉晶速率制备合金试样具有较长的蠕变寿命和较高的伸长率,合金蠕变期间裂纹萌生主要发生在碳化物处。

The effect of withdrawal rate on microstructure and creep properties at 980 ℃/235 MPa of DZ125 alloy was researched at different withdrawing rate during directional solidification by using of SEM and test of creep curves. The results show that when withdrawal rate of solidification is 1 mm/min, the size of MC type carbide was big and shape show as sheet-like structure. With the withdrawal rate increase, the size of carbide reduces, and structure change from the sheet-like to block-like. The size of γ′ decreased with the withdrawal rate increasing slightly. It was shown that the amount of initial elongation is smaller and creep strain rate is larger of low withdrawal rate alloy during the steady state creep by determination the creep curves of alloy which withdrawal rate is 1mm/min, 3 mm/min and 5mm/min at 980 ℃ /235 MPa conditions. At experimental conditions, the alloy prepared at high withdrawal rate has a longer creep life and higher elongation, and the crack initiation occurred mainly in the carbide during creep.