Abstract

The influence of the temperature–time parameters (temperature from 1000 to 1300°C, time from 1 to 500 h) of heat treatment (HT) of 〈001〉 and 〈111〉 single crystals of boron-free heterophase γ'-Ni₃Al + γ‑Ni intermetallic (IM) alloys of the Ni–Al–Cr–Mo–W–Ti(Zr)–La system (VKNA-1V) and such alloys with cobalt and rhenium (VKNA-25) on their structure, fracture, and short-term and long-term strength is studied. The introduction of cobalt and rhenium or an increase in the cooling rate of the 〈001〉 single crystals in the range 30–300°C/min is found to decrease the sizes of the structural components of all levels. In addition, the rule derived for two- and three-component nickel-based alloys is shown to be valid for γ'-Ni₃Al-based IM alloys: if an introduced alloying element (AE) increases the melting point T_m of the base metal (nickel), the AE distribution coefficient is k_d > 1 and the AE enriches dendrite arms; if AE decreases T_m of nickel, we have k_d < 1 and the AE enriches the interdendritic space. The AE dendritic microsegregation coefficients k_d weakly depend on the cooling rate during solidification, and their values decrease in the following row: Re, W, Co, Mo, Al, and Ti. An increase in the time of low-temperature HT (T < T_solvus) or an increase in the HT temperature to T_solvus ≤ T ≤ T_solidus leads to the “homogenization” of heterophase γ' + γ IM alloys. The dendritic microsegregation coefficients of all AEs except for Re approach unity, and interdendritic nonequilibrium \(\gamma _{{{\text{pr}}}}^{'}\) and γ' + β precipitates disappear. A homogeneous γ' + γ structure, which is characteristic of IM dendrites (γ'-phase regions of irregular shape separated by continuous or discontinuous γ-phase layers), forms. It differs from the structure of nickel superalloys. This type of homogenization decreases the durability as compared to the as-cast material, which retains the maximum microsegregation heterogeneity after short-term HT in order to relieve casting stresses.

中文翻译：

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热处理后含铬、钼、钨、铼和钴的 Ni3Al-Ni-NiAl 铸造合金的结构相态和机械性能的变化

摘要

〈001〉和〈111〉无硼异相γ'-Ni ₃单晶热处理（HT）温度-时间参数（温度1000～1300℃，时间1～500 h）的影响Ni-Al-Cr-Mo-W-Ti(Zr)-La 系统 (VKNA-1V) 的 Al + γ-Ni 金属间化合物 (IM) 和这种结构上含有钴和铼的合金 (VKNA-25)，断裂，并研究短期和长期强度。发现钴和铼的引入或 <001> 单晶的冷却速率在 30-300°C/min 范围内的增加可以减小各级结构组件的尺寸。此外，从二组分和三组分镍基合金推导出的规则表明对 γ'-Ni ₃有效铝基IM合金：如果引入的合金元素（AE）提高了母材（镍）的熔点T _m，则AE分布系数k _d > 1，AE富集枝晶臂；如果 AE 降低镍的T _m，我们有k _d < 1 并且 AE 丰富了枝晶间空间。AE 枝晶微偏析系数k _d与凝固过程中的冷却速度有微弱的关系，它们的值在以下行中减小：Re、W、Co、Mo、Al 和 Ti。低温 HT 时间增加（T < T _solvus）或 HT 温度增加到T_固溶线≤ T ≤ T_固相线导致异相γ' + γ IM 合金的“均质化”。除 Re 外，所有 AE 的枝晶微偏析系数接近统一，枝晶间非平衡\(\gamma _{{{\text{pr}}}}^{'}\)和 γ' + β 沉淀消失。形成均匀的 γ' + γ 结构，这是 IM 枝晶（由连续或不连续 γ 相层隔开的不规则形状的 γ' 相区域）的特征。它不同于镍高温合金的结构。与铸态材料相比，这种类型的均质化降低了耐用性，铸态材料在短期高温热处理后保留了最大的微观偏析不均匀性，以减轻铸造应力。