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Hf和Zr促进了γ+γ′共晶、MC_((2))和Ni5M相的生成。在含等原子百分数Zr和Hf的合金中,Zr在共晶γ′内的溶解度比Hf低,Ni_5M相中Zr含量比Hf高。Zr的这种分布有利于形成Ni_5M相,降低了Zr的强化效果。1130℃/3小时处理有效地消除了Ni_5M相,因此使合金的初熔温度升高。1100℃/4小时沉淀处理形成尺寸为0.5μm的立方状γ′沉淀,在760～1050℃整个温度范围使含Hf合金的蠕变强度远高于不含Hf的合金。与无Hf合金相比,含Hf合金的低周疲劳(LCF)寿命更长。当以Zr部分或全部代替Hf时也有类似的倾向。更高的凝固速度由于组织更细和取向更优而延长了LCF寿命。表面滑移分析表明,含Hf和不含Hf合金中相邻晶粒都出现两组滑移交割,但无Hf合金的柱晶界易出现开裂。Mar-M200合金LCF试样表面裂纹数目和单位面积上裂纹长度很高。MC开裂主要发生在垂直应力轴方向的长条形碳化物上,然后向枝晶间区扩展。含Hf合金则由于滑移带的分离而沿结晶学平面开裂。
Hf and Zr promoted the formation of γ + γ ’eutectic, MC _ ((2)) and Ni_5M phases. In alloys containing equal atomic percentages of Zr and Hf, the solubility of Zr in the eutectic γ ’is lower than that of Hf, and the Zr content in the Ni_5M phase is higher than that of Hf. This distribution of Zr favors the formation of the Ni_5M phase, reducing the strengthening effect of Zr. The 1130 ° C / 3 hour treatment effectively eliminated the Ni_5M phase, thereby increasing the initial melting temperature of the alloy. A cubic γ ’precipitate of 0.5 μm in size was precipitated at 1100 ° C for 4 hours and the creep strength of the Hf-containing alloy was much higher than that of the Hf-free alloy over the entire temperature range of 760 to 1050 ° C. Low cycle fatigue (LCF) life of Hf-containing alloys is longer than that of Hf-free alloys. A similar tendency also appears when Hf is partially or completely replaced by Zr. Higher solidification rates extend LCF life due to finer tissue and better orientation. Surface slip analysis shows that there are two groups of slip delivery for adjacent grains in both Hf and non-Hf-containing alloys, but no crack occurs in the grain boundaries of the Hf-free alloys. The crack number and the crack length per unit area of Mar-M200 alloy LCF sample are very high. MC cracking mainly occurs in the direction of the vertical stress axis of the elongated carbide, and then extended to the interdendritic region. Hf-containing alloys then crack along the crystallographic plane due to the separation of slip bands.