Crystallographic Orientation and Chemical Composition Dependence of Creep and High Temperature Fatigue Strength of Single Crystals of Ni-Base Superalloys.

A.本研究的目的是研究不同化学成分的镍基高温合金单晶体的屈服强度、蠕变强度和疲劳强度的取向依赖性，以显示具有优良性能的合金，供实际使用。本研究的步骤和结果1）材料：三种镍基高温合金，1）Al-Ti-Ta型，2）Al-Ti-V型，3）Al-Si型。2）拉伸试验：三种合金的单晶在室温至1000 ℃下进行拉伸试验。研究了屈服应力和CRSS的取向依赖性。在700 ℃附近，[001]取向的合金具有最高的强度。在900 ° C和1000 ° C下，合金2和3在[001]方向上具有最高强度，而合金1在[115]和[014]方向上表现出最高强度。3）蠕变强度：对合金1和2进行蠕变测试。典型的5个低指数方向是： 关于我们 被选为初始拉伸取向。测试温度为700 ℃和9000 ℃。在7000 ℃时，与合金1和2中的其他取向相比，[001]表现出最长的断裂时间。然而，在9000 ℃时，[113]或[111]的断裂时间比[001]长。如果在相同的测试条件下进行比较，则合金1与合金2相比具有更长的断裂时间。4）高温疲劳：使用具有[001]、[011]和[111]取向的合金1在7000 ° C下进行高周疲劳测试。施加的应力形式为完全反对称的三角形拉伸形式，频率为5 Hz。三个方向的S-N曲线彼此相似。因此，发现疲劳强度的取向依赖性小。结论：根据以往的研究，[001]取向是最强的取向。然而，在本研究中，得到了不同的结果，即屈服强度的取向依赖性，蠕变强度的取向依赖性和疲劳强度的取向依赖性彼此不同。在屈服强度和蠕变强度方面，在相同的测试条件下，合金1与合金2相比表现出更高的强度。少

A. The purpose of the present studyThe purpose of the present study is to examine the orientation dependence of yield, creep and fatigue strengths of single crystals of Ni-base superalloys with different chemical compositions, and to show the alloy with excellent properties for practical use.B. Procedures and results of the present study1) Materials: Three kinds of Ni-base superalloys, 1) Al-Ti-Ta type, 2) Al-Ti-V type, 3) Al-Si type.2) Tensile tests: Single crystals of the three kinds of alloys were subjected to tensile tests at room temperature up to 1000ﾟC. Orientation dependences of proof stress and CRSS were examined. Around 700ﾟC, the [001] orientation had the highest strength in three kinds of alloys. At 900ﾟC and 1000ﾟC, the alloys 2 and 3 had the highest strength in the [001], while the alloy 1 exhibited the highest strength in the [115] and [014] orientations.3) Creep strength: The alloys 1 and 2 were subjected to creep tests. Typical five orientations with low indices were s … More elected as the initial tensile orientations. Testing temperatures were 700ﾟC and 9000ﾟC. At 7000ﾟC, the [001] exhibited the longest rupture times compared with those of the other orientations in both the alloys 1 and 2. At 9000ﾟC, however, the [113] or [111] showed longer rupture times than the [001]. The alloy 1 had longer rupture times compared with the alloy 2, if compared in the same testing conditions.4) High temperature fatigue: The high cycle fatigue tests were performed at 7000ﾟC using the alloy 1 with the orientations of [001], [011] and [111]. The form of applied stress was a perfectly antisymmetric triangular form in tension.The frequency was 5Hz. The S-N curves of the three orientations were resembled each other. Thus, it was found that the orientation dependence of fatigue strength is small.C. Conclusions: According to the previous studies, it has been reported that the [001] orientation is the strongest orientation. In the present study, however, the different results have been obtained, i.e. the orientation dependence of yield strength, that of creep strength and that of fatigue strength were different each other. In both the yield strength and creep strength, the alloy 1 exhibited higher strengths compared with the alloy 2 in the same testing condition. Less