發(fā)布時(shí)間：2018-06-05 04:12

  本文選題：非晶合金 + 預(yù)壓縮處理��； 參考：《蘭州理工大學(xué)》2017年碩士論文

【摘要】：由于非晶體金屬材料具有特殊的組織結(jié)構(gòu),其原子在三維空間中呈現(xiàn)出短程有序而長程無序的混亂排列,因此具備一些優(yōu)于晶體金屬材料的物理及化學(xué)性能,如高強(qiáng)度、低彈性模量及良好的耐腐蝕性能等,憑借這些優(yōu)點(diǎn),此類材料受到國內(nèi)外研究學(xué)者的廣泛關(guān)注。但也正是這種特殊的原子排列方式,使得非晶體金屬材料具有較差的室溫塑性,脆性斷裂的破壞方式限制了其在工程上的應(yīng)用。微小的形變加工及元素?fù)诫s能夠在一定程度上使非晶合金的室溫塑性得到提升。因此,本文基于Zr基非晶合金的研究現(xiàn)狀,選取了非晶形成能力好,但室溫塑性差的Cu_(36)Zr_(48)Al_8Ag_8為研究對(duì)象,對(duì)其進(jìn)行微小彈性預(yù)壓處理及添加合金化元素Ni和Nb,探究這兩種方式對(duì)Cu_(36)Zr_(48)Al_8Ag_8非晶合金室溫塑性的影響。其中微小彈性預(yù)壓處理的具體過程為:對(duì)非晶合金試樣施加低于其屈服載荷的壓應(yīng)力,使試樣僅發(fā)生線彈性或滯彈性變形,卸載后無宏觀永久變形。在此基礎(chǔ)上研究不同方式的預(yù)壓工藝參數(shù)(不同壓力、保壓時(shí)間及循環(huán)次數(shù))的影響權(quán)重,確定最佳工藝,并采用此種工藝參數(shù)為實(shí)驗(yàn)手段,通過差示掃描量熱分析(DSC)非晶合金增塑的具體微觀機(jī)理;元素?fù)诫s的具體過程為:采用銅模吸鑄技術(shù)制備出一系列直徑為3 mm的(Cu_(0.36)Zr_(0.48)Al_(0.08)Ag_(0.08))100-x Nix(x=0、2、4、6)及(Cu_(0.36)Zr_(0.48)Al_(0.08)Ag_(0.08))100-x Nbx(x=0、1、2、4)棒狀試樣,使用X射線衍射儀(XRD)、透射電子顯微鏡(TEM)及掃描電子顯微鏡(SEM)對(duì)元素?fù)诫s后的試樣進(jìn)行微觀組織結(jié)構(gòu)分析,確定元素?fù)诫s對(duì)非晶合金室溫塑性影響的原因。兩者實(shí)驗(yàn)方法的力學(xué)性能均通過萬能力學(xué)試驗(yàn)機(jī)進(jìn)行測(cè)定。研究結(jié)果表明:(1)Cu_(36)Zr_(48)Al_8Ag_8非晶合金試樣在經(jīng)過預(yù)壓縮處理后,室溫塑性均產(chǎn)生了相應(yīng)的變化,確定了最佳的工藝參數(shù),并得出循環(huán)次數(shù)對(duì)試樣室溫塑性的變化影響最大,保壓時(shí)間次之,而壓力對(duì)試樣室溫塑性的變化影響較小;(2)Cu_(36)Zr_(48)Al_8Ag_8非晶合金試樣內(nèi)自由體積的含量隨保壓時(shí)間的變化而變化且剪切帶的擴(kuò)展及增殖方式也與自由體積的含量成正比例關(guān)系;(3)適量Ni元素的添加促進(jìn)了試樣的相分離程度,產(chǎn)生小尺寸晶體相,改善試樣的室溫塑性;(4)適量Nb元素的添加能夠促進(jìn)B2-Cu Zr增韌相的析出,并抑制其發(fā)生共析分解,改善試樣的室溫塑性。
[Abstract]:Because of the special structure of amorphous metal materials, the atoms of amorphous metal materials exhibit short range ordered and long range disordered arrangement in three dimensional space, so they have some better physical and chemical properties than crystal metal materials, such as high strength. With the advantages of low modulus of elasticity and good corrosion resistance, this kind of material has been widely concerned by researchers at home and abroad. However, it is precisely this special arrangement of atoms that makes amorphous metal materials have poor room temperature plasticity, and the failure mode of brittle fracture restricts their application in engineering. The room temperature ductility of amorphous alloys can be improved to a certain extent by micro deformation processing and element doping. Therefore, based on the current research situation of Zr-based amorphous alloys, Cu_(36)Zr_(48)Al_8Ag_8 with good amorphous forming ability but poor room temperature plasticity is selected as the research object. Micro elastic preloading and adding alloying elements Ni and NB were carried out to investigate the effect of these two methods on the room temperature plasticity of Cu_(36)Zr_(48)Al_8Ag_8 amorphous alloys. The specific process of micro-elastic preloading is that the specimen is subjected to compressive stress lower than its yield load, so that only linear elastic or anelastic deformation occurs, and no macroscopic permanent deformation occurs after unloading. On this basis, the influence weight of different preloading process parameters (different pressure, pressure holding time and cycle times) was studied, and the optimum process was determined, and the process parameters were used as experimental means. By differential scanning calorimetry (DSC), the specific microcosmic mechanism of plasticization of amorphous alloys was analyzed. The specific process of element doping was as follows: a series of copper mould suction casting technique was used to prepare a series of corrugated samples with a diameter of 3 mm. A series of Cupperton 0.36Nixx02446) rod specimens were prepared. X-ray diffractometer (XRD), transmission electron microscopy (TEM) and scanning electron microscope (SEM) were used to analyze the microstructure of the doped samples, and to determine the reasons for the effect of doping on the ductility of amorphous alloys at room temperature. The mechanical properties of both methods were measured by universal mechanical testing machine. The results show that after precompression treatment, the plastic properties of the amorphous alloy samples have changed at room temperature, and the optimum technological parameters have been determined. The results show that the cyclic times have the greatest influence on the room temperature plasticity of the samples, and the holding time is the second. The effect of pressure on the plasticity at room temperature is relatively small, and the free volume content in the sample varies with the holding time, and the expansion and propagation mode of the shear band is proportional to the free volume content. The addition of appropriate amount of Ni promoted the phase separation of the sample. The addition of appropriate NB element can promote the precipitation of B2-Cu Zr toughened phase, restrain the eutectoid decomposition, and improve the room temperature plasticity of the sample.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG139.8;TG306

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本文編號(hào)：1980443