本文研究了定向凝固DZ38G合金热疲劳性能及其组织结构的变化,并与其原型合金M38G对比.由于DZ38G合金消除了横向晶界和弹性模量低等原因,抗热疲劳性能有很大提高.热疲劳裂纹一般萌生在晶界或相界面,沿着枝晶间或晶界扩展,有时裂纹也沿着一定晶体学方向传播.合金经热疲劳后,晶界碳化物增多,γ′形态发生变化,并观察到裂纹两侧存在γ′相贫化和再结晶现象.
The thermal fatigue behaviour and microstructure in a direction-ally solidified DZ38G alloy have been investigated. It was found that DZ38G alloyhas larger thermal fatigue resistance than that of original M38G alloy because of theelimination of the transverse grain boundaries and the increasing of elastic modulus.Detailed observations show that the microcrack is initiated at the grain boundariesor the phase interface and propagates along interdendrites, grain boundaries and,sometimes, the defined crystallographic directions. After thermal fatigue test, theamount of carbides at grain boundaries increases and the morphology of γ′ phasebecome irregular. Both γ′denudation and recrystallization have been observed onboth sides of the crack.
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