TiNi基金属玻璃复合材料的组织和力学性能研究

发布时间：2018-06-19 23:45

本文选题：非晶复合材料 + 形状记忆晶相　；参考：《兰州理工大学》2016年硕士论文

【摘要】：本文选择具有形状记忆效应和较强非晶形成能力的(Ti_(0.5)Ni_(0.5))100-xCux系合金,研究了铜含量变化(x=0,10,15,20,25,30,35,40)对(Ti_(0.5)Ni_(0.5))100-xCux合金系组织和力学性能的影响,优化出综合力学性能优异的(Ti_(0.5)Ni_(0.5))80 Cu20合金,其断裂强度为2246MPa,压缩塑性达到12.2%,组织中仅为非晶基体和过冷奥氏体相B2-Ti(Ni,Cu)和热致马氏体相B19’-Ti(Ni,Cu),而无其他金属间化合物相,应力加载形变过程中通过形状记忆晶相TRIP效应对非晶基体增韧,并表现出强烈加工硬化行为。在此基础上,研究了(Ti50Ni50-y My)_(80)Cu_(20)合金体系,M=Zr或Co,其中,Zr为提高马氏体相变温度元素,促进凝固组织中马氏体的相转变,但能够明显提高非晶形成能力;Co为降低马氏体相变温度元素,稳定凝固组织中奥氏体相析出。当M=Co,y=0.02时,非晶复合材料的压缩断裂强度为2582MPa,塑性应变为15%。在前述成分优化的基础上,分别设计了半固态处理工艺和预变形退火工艺,进一步优化组织结构并提高力学性能,本文得出结论如下:(1)随着铜含量的增大,(Ti_(0.5)Ni_(0.5))100-x Cux合金的非晶形成能力呈现一个从上升、降低再到上升的波形变化,但总体呈现降低趋势。优化出具有综合力学性能最优的成分点,即在x=20时,合金有最高的断裂强度2246MPa,且其产生了12.2%塑性应变。(2)随着Zr的不断添加,此系列非晶合金非晶形成能力先提高后降低,凝固过程的温度梯度决定了复合材料的组织梯度,由表及里,主要为非晶相、马氏体相和奥氏体树枝晶相。随着非晶形成能力提高,非晶相体积分数增加。而整个研究成分体系中,随着Zr的添加,奥氏体含量不断下降,相变诱发塑性减弱,从而塑性逐级递减,强度先升高后降低。(Ti0.5Ni0.48Zr0.02)_(80)Cu_(20)的断裂强度达到2345MPa,塑性应变达10.1%;随着钴的不断添加,奥氏体含量不断升高,相变诱发塑性增强,从而塑性逐渐上升致奥氏体达到饱和时下降,强度先升高后下降,(Ti0.5Ni0.48Co0.02)80 Cu20的综合性能最佳,断裂强度达到2582MPa,塑性应变达15%。加载时形变诱导相变对非晶基体同时增强增韧,复合材料的综合力学性能优异,以连续屈服和强烈的加工硬化为主要特征。(3)(Ti_(0.5)Ni_(0.5))_(80)Cu_(20)和(Ti0.5Ni0.48Co0.02)80 Cu20试样的组织为晶相和非晶相的复合结构,晶相为过冷奥氏体和热致马氏体结构,应力加载诱发奥氏体相转变为马氏体并择优取向,使复合材料强度和塑性同时提高并出现加工硬化行为。铸态试样的心部组织为较粗大的树枝晶,且生长不均匀,经半固态处理后,复合材料组织得到有效优化,获得奥氏体相晶粒细小、圆整度高、组织致密;随着预变形程度的增加,(Ti_(0.5)Ni_(0.5))80 Cu20合金中马氏体相和奥氏体相均增加,而马氏体相增加的更快,复合材料的屈服强度提高,塑性减小,塑形阶段预变形能够实现屈服强度可控。
[Abstract]:In this paper, we have studied the effect of the change of copper content on the microstructure and mechanical properties of TiTiG 0.5Nix 100-xCux alloy system with shape memory effect and strong amorphous formation ability. The effect of copper content change on the microstructure and mechanical properties of TiTiG 0.5NiU 0.5NiCX alloy system has been studied, and the excellent comprehensive mechanical properties have been optimized. The fracture strength is 2246MPa, the compressive plasticity reaches 12.2mm, the microstructure is composed of amorphous matrix and undercooled austenite phase B2-TiTiNiNiCuCu) and thermally induced martensite phase B19-TiNiNiNiCU, but there are no other intermetallic compound phases. During stress loading and deformation, the amorphous matrix is toughened by shape memory crystal phase trip effect and shows strong work hardening behavior. On the basis of this, the alloy system of Ti50Ni50-y Myai _ (80) / C ~ (+) / C _ (20) is studied, in which Zr is used to increase the martensite transformation temperature element and to promote the martensite phase transformation in solidified microstructure, but the amorphous formation ability and Co is the decreasing martensite transformation temperature element. Austenitic phase precipitates in stable solidified microstructure. The compressive fracture strength of the amorphous composite is 2582 MPA and the plastic strain is 15%. On the basis of the composition optimization mentioned above, the semi-solid treatment process and pre-deformation annealing process were designed respectively to further optimize the microstructure and improve the mechanical properties. The conclusion is as follows: (1) with the increase of copper content, the amorphous forming ability of titips 0.5 / Nix / x Cux alloy shows a waveform change from rising, decreasing to rising, but the overall trend is decreasing. The optimum composition point with comprehensive mechanical properties is optimized, that is, at x = 20:00, the alloy has the highest fracture strength of 2246MPa, and it produces a plastic strain of 12.2wt%.) with the addition of Zr, the amorphous forming ability of this series of amorphous alloys increases first and then decreases. The temperature gradient of the solidification process determines the microstructure gradient of the composite, which is mainly amorphous phase, martensite phase and austenitic dendritic phase from surface to interior. The volume fraction of amorphous phase increases with the increase of amorphous forming ability. In the whole composition system, with the addition of Zr, the content of austenite decreases and the ductility induced by transformation weakens, and the plasticity decreases gradually. The fracture strength of Ti0.5Ni0.48Zr0.02C _ (+) and the plastic strain reaches 2345MPa, and the plastic strain reaches 10.1.The austenite content increases continuously with the addition of cobalt, and the ductility is enhanced by transformation, so the plasticity increases gradually, and the austenite decreases when the austenite reaches saturation, and the ductility increases gradually, and the ductility decreases when the austenite reaches saturation, with the addition of cobalt, the austenite content increases continuously, and the ductility increases. The comprehensive properties of Ti0.5Ni0.48Co0.02Cu20 are the best, the fracture strength is 2582MPa, and the plastic strain is 15%. Under loading, deformation induced phase transformation strengthens and toughens the amorphous matrix at the same time. The composite material has excellent comprehensive mechanical properties. The main characteristics of the composites are continuous yield and strong work hardening. The main features of the composites are continuous yield and strong work hardening. The microstructure of the Ti0.5Ni0.48Co0.02O80Cu20 and Ti0.5Ni0.48Co0.02O80Cu20 specimens are the composite structures of the crystalline phase and the amorphous phase. The crystal phase is supercooled austenite and thermo-induced martensite structure. The austenite phase is transformed into martensite and preferred orientation by stress loading. The strength and plasticity of the composites increase and work hardening behavior occurs. The core structure of the as-cast sample is a coarse dendrite with uneven growth. After semi-solid treatment, the microstructure of the composite is optimized effectively, and the austenitic phase is obtained with fine grain size, high roundness and dense microstructure. With the increase of predeformation degree, both martensite phase and austenitic phase increase, but martensite phase increases more rapidly, the yield strength increases and the plasticity decreases. The yield strength can be controlled by pre-deformation in the plastic stage.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB33

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