【摘要】：塊體非晶合金變形是通過高度局域化的剪切帶形成及擴(kuò)展來實(shí)現(xiàn),其特征是塑性變形集中于剪切帶內(nèi)部,合金的脆性與這種不均勻變形行為密切相關(guān),因此非晶合金的塑性與形變過程剪切帶的空間增殖密切相關(guān)。本文使用循環(huán)加載模式,通過控制加載載荷及頻率,對Zr52.5Cu179Ni1i4.6Al10Ti5(Vit.105)塊體非晶合金試樣進(jìn)行彈性預(yù)加載處理。通過研究經(jīng)預(yù)加載處理試樣的微觀結(jié)構(gòu)演化規(guī)律,分析了不同預(yù)加載模式對Vit.105塊體非晶合金力學(xué)性能的影響規(guī)律,探討了合金鋸齒流變現(xiàn)象及其與合金剪切帶空間增殖能力的關(guān)聯(lián),主要研究結(jié)果如下:預(yù)加載處理并不導(dǎo)致Zr52.5Cu179Ni146Al10Ti5塊體非晶合金發(fā)生晶化,但使其原子結(jié)構(gòu)的空間構(gòu)型發(fā)生變化,發(fā)生體積擴(kuò)張,導(dǎo)致合金自由體積含量增加,如頻率的增加引起合金結(jié)構(gòu)弛豫焓變AHr增大,頻率增至30Hz時,處理后合金的△Hr增加到-11.3J/g。高載荷預(yù)處理導(dǎo)致合金顯微硬度下降,如7KN及8KN處理后合金硬度值低于鑄態(tài)合金,處理后合金的塑性應(yīng)變值均較鑄態(tài)合金顯著增加,表明循環(huán)載荷加載處理提高了合金的塑性性能,6KN、20Hz時合金具有最佳的塑性變形能力。合金斷口及側(cè)面形貌表明,頻率越高、載荷越大合金內(nèi)部溫升越高;同時側(cè)面剪切帶數(shù)量有所增加,互相交錯阻礙了剪切帶擴(kuò)展。分析預(yù)處理試樣壓縮應(yīng)力-應(yīng)變曲線上的鋸齒流變行為,發(fā)現(xiàn)合金塑性的提高是由于處理后合金內(nèi)增加的自由體積使剪切帶更易形核,同時溫升幅度較小的合金內(nèi)部粘度及溫度的回復(fù)更快,兩者協(xié)同進(jìn)行提高了合金的塑性。
[Abstract]:The deformation of the bulk amorphous alloy is realized by the formation and expansion of the highly localized shear band, which is characterized by the plastic deformation concentrated in the shear zone. The brittleness of the alloy is closely related to this nonuniform deformation behavior. Therefore, the plasticity of the amorphous alloy is closely related to the space proliferation of the shear zone. Zr52.5Cu179Ni1i4.6Al10Ti5 (Vit.105) bulk amorphous alloy specimens were preloaded by elastic preloading by controlling loading load and frequency. The influence of different preloading modes on the mechanical properties of Vit.105 bulk amorphous alloys was analyzed by studying the microstructure evolution of preloaded samples, and the alloy saw tooth was discussed. The main results are as follows: the preloading treatment does not lead to the crystallization of Zr52.5Cu179Ni146Al10Ti5 bulk amorphous alloy, but the spatial configuration of the atomic structure changes and the volume expansion occurs, resulting in the increase of the free volume content of the alloy, such as the increase of frequency. When the alloy structure relaxation enthalpy AHr increases and the frequency increases to 30Hz, the alloy's Delta Hr increases to the -11.3J/g. high load preconditioning leads to the decrease of the alloy microhardness. For example, the hardness of the alloy after 7KN and 8KN treatment is lower than the cast alloy. The plastic strain value of the alloy after treatment is significantly higher than that of the cast alloy, indicating that the cyclic loading treatment is improved. The alloy has the best plastic deformability at 6KN and 20Hz. The alloy fracture and profile show that the higher the frequency and the larger the load, the higher the internal temperature of the alloy, and the increase in the number of the lateral shear bands, which obstruct the expansion of the shear band. It is found that the increase of the plasticity of the alloy is due to the increase of the free volume in the alloy after treatment, which makes the shear band more easy to nucleate, and the internal viscosity and temperature of the alloy with less temperature rise are faster, and the two synergies improve the plasticity of the alloy.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG139.8

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本文編號：2137531