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Al2O3sf/ZL109复合材料的热疲劳短裂纹的扩展行为 总被引:9,自引:0,他引:9
在室温至280℃间热循环条件下,研究了体积百分含量18%的氧化铝短纤维增强ZL109铝-硅合金复合材料和基体ZL109铝-硅合金的热军短裂纹扩展行为,并且探讨和复皮劳裂纹的形成机制和扩展过程。研究结果显示,短裂纹扩展阶段,热疲劳裂纹与增强体纤维有明显的交互作用,但复合材料的皮劳短裂纹扩展速率比基体合金的大,加强基体与纤维的界面结合,提高纤维质量,可望提高复合材料的热疲劳裂纹扩展抗力。 相似文献
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DZ40M合金的热疲劳性能 总被引:2,自引:0,他引:2
采用扫描电子显微镜研究DZ40M定向凝固钴基高温合金的热疲劳性能。结果表明,随着上限温度的升高,裂纹扩展速率增加,热疲劳抗力降低。在上限温度相同时,随着保温时间的延长,热疲劳性能提高,在合金表面形成均匀致密的氧化物保护膜有利于热疲劳性能的提高。由于碳化物与基体的热膨胀系数不同,合金在受温度交替变化时,易在基体和碳化物界面处产生裂纹孔洞,从而萌生裂纹。热疲劳裂纹通过裂纹孔洞的相互连接向前扩展 相似文献
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DZ951合金的热疲劳性能 总被引:1,自引:0,他引:1
研究了不同上限温度对DZ951合金热疲劳性能的影响.结果表明:随着上限温度的升高,热疲劳裂纹扩展速率增加,合金的热疲劳抗力降低.DZ951合金经热处理后,热疲劳性能提高.合金主要通过氧化产生孔洞,孔洞相互连接使热疲劳裂纹萌生和扩展.合金热疲劳裂纹扩展具有一定的晶体学取向,沿{111}面〈110〉方向即与枝晶生长方向呈45°角扩展. 相似文献
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用自约束试验方法研究了Cr18W2合金白口铸铁的热疲劳性能,用扫描电镜观察了热疲劳断口。结果表明:合金白口铸铁的热疲劳抗力主要与热处理硬度有关,随硬度升高,热疲劳裂纹扩展速度增大,热疲劳抗力降低。热疲劳抗力对基体的显微组织不敏感。 相似文献
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《热加工工艺》2017,(24)
研究了温度幅分别为25~300℃、25~350℃和25~400℃时,铸态A356合金、细化变质A356合金、微合金化A356合金和T6态微合金化A356合金的热疲劳行为;分析了热裂纹萌生和生长的机理。结果表明,在相同温度幅下,热疲劳裂纹萌生寿命从大至小的顺序为:T6态微合金化A356合金、微合金化A356合金、细化变质A356合金、铸态A356合金;在热疲劳裂纹形成后,裂纹扩展早期阶段的裂纹生长速度要高于扩展后期;铸态A356合金和细化变质A356合金的热疲劳裂纹呈弯曲状且主要以沿晶方式扩展;微合金化A356合金和T6态微合金化A356合金的热疲劳裂纹更加平直和细小,且以穿晶-沿晶的混合方式扩展;T6态微合金化A356合金具有最佳的抗热疲劳性能。 相似文献
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研究了WC-Co系硬质合金的热冲击疲劳行为。结果表明,热冲击疲劳裂纹的萌生有一定的孕育期。它的热冲击行为与热循环温度、粘结相含量和冷却速度有关。热循环温度越高,冷却速度越快,则裂纹萌生孕育期越短,裂纹扩展速率越快,吉相含量越高,理解纹萌生孕育期变短,热冲击疲劳断口有明显的疲劳条纹特征。 相似文献
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J. Sobczak N. Sobczak P. Darlak Z. Slawinski R. Asthana P. Rohatgi 《Journal of Materials Engineering and Performance》2002,11(6):595-602
The thermal fatigue resistance of AlSi alloys and discontinuously reinforced Al-matrix composites containing graphite, silicon
carbide, and fly ash particulates, and short alumina (Saffil) fibers was characterized by measuring the total length of microcracks
on gravity-cast and squeeze-cast test specimens as a function of number of thermal cycles (1000–5000 cycles, 270 K amplitude).
In each thermal cycle, the test specimens were heated and stabilized in air at 375 °C, water quenched, and air stabilized.
In all specimens, the total crack length on a specified region increased with increasing number of thermal cycles. Whereas
among monolithic alloys, squeeze-cast Al-12SiCuNiMg alloy exhibited better resistance to thermal cracking than Al-25Si and
Al-20SiNi alloys, among the composites, squeeze-cast Al-alumina and Al-fly ash composites exhibited the best thermal fatigue
resistance. The theoretical estimates of the thermal fatigue resistance of these composites are consistent with the experimental
observations. 相似文献
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以Al-6Mg-0.8Zn-0.5Mn-0.2Zr-0.2Er合金为基础,对该材料的冷轧态,温轧态,完全退火态进行拉伸测试和疲劳裂纹扩展速率测试。运用电子背散射衍射(EBSD),透射电镜(TEM),扫描电镜(SEM)对合金的原始组织、疲劳断口、裂纹扩展路径进行观察,研究微观组织对材料拉伸性能及疲劳裂纹扩展速率的影响。结果表明:温轧态屈服强度高,裂纹扩展抗力大,实现了高强高耐损伤性能的匹配。这主要是由于温轧态轧制过程中发生动态回复,位错缠结规整化,具有较多的亚晶界,该种组织模式对材料的屈服强度和疲劳裂纹扩展抗力均有提高。 相似文献
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Fatigue behavior has been studied on gas-nitrided smooth specimens of commercial pure titanium, an alpha/beta Ti-6Al-4V alloy,
and a beta Ti-15Mo-5Zr-3Al alloy under rotating bending, and the obtained results were compared with the fatigue behavior
of annealed or untreated specimens. It was found that the role of the nitrided layer on fatigue behavior depended on the strength
of the materials. Fatigue strength was increased by nitriding in pure titanium, while it was decreased in the Ti-6Al-4V and
Ti-15Mo-5Zr-3Al alloys. Based on detailed observations of fatigue crack initiation, growth, and fracture surfaces, the improvement
and the reduction in fatigue strength by nitriding in pure titanium and both alloys were primarily attributed to enhanced
crack initiation resistance and to premature crack initiation of the nitrided layer, respectively. 相似文献
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微量元素对AlCu4.5合金力学性能的影响 总被引:4,自引:0,他引:4
高强度铸造Al-Cu合金具有良好的室温和高温国强度,但它的热裂倾向性一直是制约其发展的瓶颈,通过对合金的收缩应变和热裂抗力及准固态力学行为进行测试,研究了微量合金元素(Ni,Si,Ce,La,Ti,Zr,Mn)对AlCu4.5合金准固态力学性能的影响。结果表明,Si,Ce,La,Ti,Zr合金元素能使AlCu4.5的热裂倾向性降低,加入质量分数为2%的Si会使合金的再辉现象非常严重,导致合金不可能有很高的强度而很快断裂,与其他AlCu4.5Si合金相比,AlCu4.5Si3合金具有很强的补缩能力,断裂应力值最高;La的加入能缩小二次枝晶间距,明显提高合金的抗热裂性能。 相似文献
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合金元素对铸造Al-4.5Cu合金准固态力学行为的影响 总被引:3,自引:0,他引:3
研究了铸造Al-4.5Cu合金的准固态力学行为及几种合金元素对其凝固行为的影响。结果表明:Si,Ce,La,Ti及Zr元素可有效减小Al-4.5Cu合金的结晶范围,从而使其热裂倾向性降低;La元素的加入可提高Al-4.5Cu合金的热裂抗力:并研制了一种新型Al-4.5Cu合金,该合金具有良好的室温与高温综合性能。 相似文献
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热应力作用下碳化钨基钢结硬质合金梯形裂纹的形成机理 总被引:2,自引:0,他引:2
在自约束型热疲劳试验机上对碳化钨含量不同的钢结硬质合金进行了热疲劳试验,用金相显微镜和扫描电镜对热疲劳裂纹扩展行为进行了研究。结果表明:在热应力作用下,不仅在合金的表面,在合金的内部都形成了“梯形”裂纹。这种形态的裂纹是由试样缺口处的热疲劳裂纹扩展而引起的,合金中的钢基体相阻碍裂纹扩展,而WC硬质相诱导裂纹扩展,这两种因素的综合作用促使热疲劳裂纹成“梯形”扩展。分析认为:使WC粒子在钢基体中均匀分布,提高钢基体的热疲劳抗力,从而来阻止梯形裂纹的形成,是提高碳化钨钢锆硬质合金抗热疲劳性能的有效途径。 相似文献
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Marco A. García-Bernal D. Hernandez-Silva V. M. Sauce-Rangel 《Journal of Materials Engineering and Performance》2012,21(7):1500-1503
In this study, the effect of Cu content on the superplastic-like behavior of Al-Mg alloys in coarse grain size condition has been studied. Five hot-rolled Al-Mg alloys with different Cu concentrations (0.5, 1.0, 1.5, and 2.0?wt.%) and without Cu were prepared. Tensile test specimens were machined parallel to the rolling direction. High-temperature elongation to failure tests were performed under a constant cross-head speed condition at different strain rates and temperatures. Grain size refinement is observed as Cu addition increases. Maximum tensile elongation of 373% could be achieved in the Al-4.5%Mg-1.5%Cu alloy with an average grain size of 28???m at 500?°C and 1?×?10?2?s?1. Grain size refinement after superplastic deformation was also observed. 相似文献
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E. V. Avtokratova O. Sh. Sitdikov R. O. Kaibyshev Y. Watanabe 《The Physics of Metals and Metallography》2009,107(3):291-297
A study of the resistance to fatigue-crack growth in a submicrocrystalline alloy Al-6% Mg-0.3% Sc-0.4% Mn in combination with a precision analysis of the fracture surface of the samples has been performed. A comparison of crack resistance between coarse-grained and submicrocrystalline states of this alloy showed that only at the stage of near-threshold crack growth the velocity of fatigue-crack propagation in the submicrocrystalline state proves to be higher than that in the coarse-grained state. At the stage of linear crack growth, the fatigue-crack propagation becomes insensitive to the grain size. Upon transition to the stage of accelerated crack growth, the velocity of crack propagation in the submicrocrystalline alloy is retarded. A fractographic analysis of the fracture surface of the samples indicates that the retardation of the fatigue-crack growth in the submicrocrystalline alloy is connected with a gradual transition from the intercrystalline to the transcrystalline mechanism of fatigue fracture of the material. 相似文献
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The influencing mechanisms of elements Ti and Ce and their interactions on fracture behaviors of casting alloys Al-4.5Cu-0.6Mn were studied by observing tensile fracture behavior in quasi-solid zone under SEM and EDX instruments.The results indicate that the resistance stress against hot cracking can be improved obviously by addition of Ti, because of its grain refining function. It is also found that, when Ce is added into the alloys, besides its effect in refining crystalline, the mechanical behavior of lower melting point eutectic phase in quasi-solid zone can be improved efficiently by some compounds with Ce formed and deposited between dendrites. Therefore, a coiligating effect of Ti and Ce on improving resistance stress against hot cracking is more efficient than that only single alloy element is applied. When hot cracking occurs, grains yield at first, and then crack spreads. Both inter-grain and trans-grain fractures are observed, but the major fracture manner is brittleness. 相似文献