排序方式: 共有57条查询结果,搜索用时 15 毫秒
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采用螺旋选晶法制备Ni3Al基单晶合金IC6SX试棒, 研究了不同拉晶速率对凝固组织和高温持久性能的影响. 结果表明, Ni3Al基单晶合金IC6SX凝固组织为树枝状, 随着拉晶速率从1.5 mm/min增加到6 mm/min, 一次枝晶间距逐渐减小. 与普通镍基高温合金不同, 位于枝晶干处的次生γ'相尺寸比枝晶间处的大. 随着拉晶速率的增加, 枝晶干和枝晶间处的γ'相尺寸都逐渐减小, 由不规则形状逐渐立方化, 枝晶间处的初生γ'相的数量逐渐增多. 一次枝晶间距和γ'相尺寸对高温持久性能影响显著, 随着拉晶速率的增加, 组织细化, 铸态IC6SX单晶合金的高温持久寿命增加. 相似文献
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Nb-16Si-24Ti-6Cr-6A1-2Hf-xCe (x =0, 0.05, 0.1,02.5, 0.5, 1 (%, atom fraction)) in situ composites were prepared by arc melting The microstmcture and the effect of rare earth element cerium on 1250℃ oxidation resistance of the composites were investigated with scanning electron microscopy (SEM) and X-ray energy disperse spectrum (EDS), as well as X-ray diffraction (XRD). The experimental results showed that the high temperature oxidation resistance of the alloy was improved by adding a proper amount of cerium (Ce). The effect of Ce was considered as the concurrent of the following three factors: first, the oxide of Ce formed in the interface reduced the internal oxidation rate; second, the lath shaped oxide containing Ce increased the cracking resistance and reduced the expansion of the oxide scale; and third, the decrease of the sificide volume fraction on account of Ce addition reduces the power of the sample resisting oxygen penetration. 相似文献
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采用多电子束物理气相沉积技术(EB-PVD)制备了总厚度为0.3mm的NiAl/Al2O3微叠层复合材料,并对该复合材料的组织结构和性能进行了研究。组织结构研究表明该复合材料具有多层的结构特征,其组织由纳米级NiAl微晶层和Al2O3层交替叠加而成。NiAl/Al2O3层界面平直清晰,NiAl颗粒和Al2O3颗粒在层界面处没有明显的混合现象。性能测试表明该材料的室温硬度值达到800HV,明显高于同制备态下的NiAl沉积薄膜,同时该材料具有良好的高温抗氧化性,其经1050℃,100h静态氧化后,氧化增重约为1.9mg/cm2,介于等原子比NiAl铸态合金的氧化增重和含有活性元素的NiAl铸态合金的氧化增重之间。组织稳定性研究表明当温度高于900℃时,该复合材料的晶粒急剧长大,多层的结构特征消失。 相似文献
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采用热模拟实验研究了Ni50Ti46-xAl4Hfx(x=0~6,at%)合金的微观组织特点和高温变形行为。合金由基体相NiTi和第二相Ti2Ni组成。Hf全部溶解在基体相和第二相中,并且促进了第二相的析出,显著提高了合金的高温强度。Ni-Ti-Al-Hf合金在700~800℃下变形行为的研究表明:合金具有良好的高温压缩性能,流变应力随着应变速率的减小或变形温度的增加而降低,其高温变形行为符合温度补偿幂规律描述。Hf的添加使合金的应力指数(n)和变形激活能(Q)上升,这主要是由于Hf的固溶强化、促进Ti2Ni相析出强化和高温稳定性造成的。 相似文献
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研究3种Ni3Al-Mo基合金在1150℃时的静态氧化行为。采用XRD、SEM和EPMA对氧化后试样的表面、截面形貌以及元素在氧化膜的分布进行研究。结果表明:氧化膜主要分为3层,最外层为NiO层,中间层由NiO、NiAl2O4及少量NiMoO4组成,最内层主要由富Al的NiAl2O4、Al2O3组成。Re元素主要分布在中间层,在氧化过程中起到"扩散障"作用,降低Al、Mo元素向外扩散的速率,促使在内层形成富铝氧化膜层以降低氧化速率,提高合金的抗氧化能力。 相似文献
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Mechanical behaviors of NiAl-Cr(Mo)-based near eutectic alloy with Ti, Hf, Nb and W additions 总被引:1,自引:1,他引:0
Effects of Ti, Hf, Nb and W alloying elements addition on the microstructure and the mechanical behaviors of NiAl-Cr(Mo) intermetallic alloy were investigated by means of XRD, SEM, EDX and compression tests. The results show that Ni-31Al-30Cr-4Mo-2(Ti, Hf, Nb, W) alloy consists of four phases: NiAl, α-Cr solid solution, Cr2Nb and Ni2Al(Ti, Hf). The mechanical properties are improved significantly compared with the base alloy. The compression yield strength at 1 373 K is 467 MPa and the room temperature compression ductility is 17.87% under the strain rate of 5.56×10-3 s-1, due to the existence of Cr2Nb and Ni2Al(Ti, Hf) phases for strengthening and Ti solid solution in NiAl matrix and coarse Cr(Mo, W) solid solution phase at cellular boundaries for ductility. The elevated temperature compression deformation behavior of the alloy can be properly described by power-law equation: ε =0.898 σ8.47exp[-615/(RT)]. 相似文献
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电磁搅拌Al—24%Si合金的显微组织 总被引:32,自引:2,他引:30
在常规凝固条件下,Al-24%Si过共晶合金中的初生Si为粗大的板片状,经过激烈的电磁搅拌,初生Si得到明显细化,分布均匀,绝大部分初生Si呈球团状或块状;搅拌功率越大,初生Si越细小和圆整,P变质可以强化电磁搅拌效果,在电磁搅拌条件下,Al-24%Si过共晶合金中的初生Si得以细化和球团化的主要原因是:电磁搅拌引起合金熔体对初生Si的机械破碎,摩擦作用,抑制初生Si择优生长作用,促进初生Si熟化和变质细化作用。 相似文献