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

本研究的目的是研究不同化学成分的镍基高温合金单晶的屈服、蠕变和疲劳强度与取向的关系，以显示该合金具有良好的实用性能。2.本研究的过程和结果1)材料：三种镍基高温合金，1)Al-Ti-Ta型，2)Al-Ti-V型，3)Al-Si型拉伸试验2)拉伸试验：将三种合金的单晶在室温至1000ﾟC的温度下进行拉伸试验，考察了应力和应变应变的取向关系。在70 0ﾟC附近，[0 0 1]取向在三种合金中强度最高。在900ﾟC和1000ﾟC下，合金2和3在[001]晶面上的强度最高，而合金1在[115]和[014]晶面上的强度最高。3)蠕变强度：对合金1和2进行蠕变试验。典型的五个方向的低指数是S…更多的被选为初始拉伸取向。试验温度分别为700ﾟC和9000ﾟC，在7000ﾟC时，合金[001]的断裂时间最长，而在9000ﾟC时，[113]或[111]的断裂时间比[001]长。在相同的试验条件下，合金1的断裂时间比合金2长。4)高温疲劳：采用[001]、[011]和[111]取向的合金1在7000ﾟC进行高周疲劳试验。施加的应力形式为完全反对称的张拉三角形，频率为5赫兹。三个方位的S-N曲线相似。因此，疲劳强度的取向依赖性很小。结论：根据以往的研究，已有报道[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、蠕变强度和疲劳强度的取向依赖关系是不同的。在相同的试验条件下，合金1的屈服强度和蠕变强度均高于合金2。较少

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