【摘要】：塊體非晶合金具有高硬度,高強度及高的彈性模量等優(yōu)異的力學(xué)性能,因此是一種應(yīng)用前景廣闊的新型材料。然而,塊體非晶合金在室溫時沒有明顯的塑性變形,這制約了非晶合金作為工程結(jié)構(gòu)材料的應(yīng)用。非晶合金的塑性變形是通過剪切帶的方式進行的,因此參與形變的剪切帶數(shù)量與非晶合金的塑性變形能力密切相關(guān)。剪切帶數(shù)量的提高有賴于形變過程中剪切帶的空間增殖,因此本文主要研究溫度及應(yīng)力作用下塊體非晶合金的微觀結(jié)構(gòu)演化及剪切帶空間增殖的關(guān)聯(lián)性,從而進一步來探究溫度及應(yīng)力對其塑性變形的影響。以Zr52.5Cu17.9Ni14.6Al10Ti5(Vit.105)和Mg58Cu30Y10塊體非晶合金為研究對象,通過納米壓痕技術(shù),研究了合金在微納米尺度的室溫蠕變行為。結(jié)果表明,在微納米尺度,兩種合金的室溫蠕變行為均與加載環(huán)境有關(guān)(如載荷及加載速率),且呈現(xiàn)明顯的成分依賴性。如,載荷越大、加載速率越快,蠕變現(xiàn)象越明顯,在同等條件下,Mg基非晶合金的蠕變位移比Vit.105合金更大。以Vit.105塊體非晶合金為研究對象,研究了溫度對非晶合金微觀結(jié)構(gòu)演化規(guī)律及塑性變形的影響。結(jié)果表明,非晶合金應(yīng)力誘發(fā)的結(jié)構(gòu)演化與測試的環(huán)境溫度密切相關(guān)。當(dāng)試樣經(jīng)40oC預(yù)壓縮處理時,其自由體積增量最大。較大的自由體積增量為非晶試樣形變過程剪切帶的空間增殖提供了大量的形核空間,促進了剪切帶的增殖,提高了非晶合金的塑性變形能力。當(dāng)溫度繼續(xù)增加時,自由體積增量減少,剪切帶的空間增殖能力減弱,且熔滴及液狀脊背的出現(xiàn)使得剪切帶在擴展過程中所受阻礙減小,降低了塊體非晶合金的塑性變形能力。
[Abstract]:Bulk amorphous alloy has excellent mechanical properties, such as high hardness, high strength and high elastic modulus, so it is a new type of material with broad application prospect. However, there is no obvious plastic deformation of bulk amorphous alloys at room temperature, which restricts the application of amorphous alloys as engineering structural materials. The plastic deformation of amorphous alloys is carried out by shear band, so the number of shear bands involved in deformation is closely related to the plastic deformation ability of amorphous alloys. The increase of the number of shear bands depends on the spatial proliferation of shear bands during deformation. Therefore, this paper mainly studies the relationship between the microstructure evolution of bulk amorphous alloys under the action of temperature and stress and the spatial proliferation of shear bands. In order to further explore the effects of temperature and stress on its plastic deformation. The creep behavior of Zr52.5Cu17.9Ni14.6Al10Ti5 (Vit.105) and Mg58Cu30Y10 bulk amorphous alloys at room temperature was studied by nano-indentation technique. The results show that the creep behavior of the two alloys at room temperature is related to the loading environment (such as loading and loading rate) at micro and nano scale, and shows obvious composition dependence. For example, the higher the load, the faster the loading rate, the more obvious the creep phenomenon. Under the same conditions, the creep displacement of Mg based amorphous alloy is larger than that of Vit.105 alloy. Taking Vit.105 bulk amorphous alloy as the research object, the effect of temperature on the microstructure evolution and plastic deformation of amorphous alloy was studied. The results show that the stress-induced structural evolution of amorphous alloys is closely related to the measured ambient temperature. When the sample is precompressed by 40oC, the free volume increment is the largest. The large free volume increment provides a large amount of nucleation space for the spatial proliferation of shear band during amorphous specimen deformation, promotes the proliferation of shear band and improves the plastic deformation ability of amorphous alloy. When the temperature continues to increase, the free volume increment decreases, the spatial proliferation ability of the shear band weakens, and the appearance of droplets and liquid ridges reduces the hindrance of the shear band in the process of expansion, which reduces the plastic deformation ability of the bulk amorphous alloy.
【學(xué)位授予單位】：長安大學(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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