具有应变硬化非晶复合材料的制备及变形行为研究

发布时间：2018-03-31 22:37

本文选题：非晶合金复合材料　切入点：加工硬化　出处：《深圳大学》2017年硕士论文

【摘要】：非晶合金是指固态合金中原子的三维空间结构呈现无序排列的合金。由于非晶合金不存在空位、位错等结构缺陷,使其具有很多独特和优异的力学、物理和化学性能,例如高强度、高断裂韧性、高硬度、大弹性极限、低弹性模量等。但非晶合金却存在一个致命的缺陷-应变软化,这极大的限制了其作为结构材料的应用。因此非晶合金的复合化是目前解决非晶合金应变软化的主要突破方向。本论文我们设计并制备了新的Ti_(38.5)Ni_(38.5)Nb_(20.5)Zr_(2.5)和Cu_(47.2)Zr_(47.2)Nb_(5.6)两种非晶复合材料,使其分别具有NiTi相和CuZr相。并通过控制制备工艺使获得的样品具有形变诱导相变的效应即TRIP(Transformation-Induced Plasticity)效应,发现两种非晶合金样品都具有优异的室温塑性变形能力并伴随明显的应变硬化现象。全新设计高Nb含量的Ti_(38.5)Ni_(38.5)Nb_(20.5)Zr_(2.5)合金含有约15%(vol)B2相,具有22.1%的工程塑性应变和高达2400MPa的抗压强度。合金的微观组织为Ni-Nb-β枝晶、B2-Ni-Ti形状记忆相和非晶基体。变形时晶态相内部产生的位错和严重的晶格畸变,导致合金具有应变硬化行为。晶内变形及对多重剪切带的诱导作用,抑制了单一剪切带的失稳扩展,从而使合金具有大的塑性应变。通过控制样品尺寸,成功制备了直径为1.0mm,1.5mm,2.0mm,2.5mm的棒状Cu_(47.2)Zr_(47.2)Nb_(5.6)非晶复合材料。复合材料由非晶基体和直径约为200nm的B2-CuZr马氏体相组成,样品具有良好的塑性变形能力和优异的应变硬化效果。复合材料的塑性变形能力随B2相的增多呈现先增多后减小的趋势,当样品直径达到1.5mm时样品含有约15%(vol)B2相,具有最高的抗压强度和11.3%的最大塑性变形,并伴随明显的应变硬化。研究表明,相变吸收弹性应变能,塑性晶体相内部的高密度位错和挛晶变形,以及非晶/晶相界面的应力集中,是引起非晶复合材料优异力学变形行为的本质原因。本研究通过合金成分设计成功制备出两个全新的非晶复合材料成分,通过第二相的增韧获得了大的塑性变形能力及明显的加工硬化,仍保持非晶基体的高强度。这为非晶合金的增韧和进一步工程化应用奠定了基础。
[Abstract]:Amorphous alloy is a kind of alloy in which the three-dimensional space structure of atoms in solid alloy is disordered. The amorphous alloy has many unique and excellent mechanical, physical and chemical properties due to the absence of vacancies, dislocations and other structural defects. For example, high strength, high fracture toughness, high hardness, large elastic limit, low modulus of elasticity, etc. Therefore, the composite of amorphous alloys is the main breakthrough direction to solve strain softening of amorphous alloys. In this paper, we have designed and prepared two kinds of new amorphous composites, Ti-Li (38.5) Nb-SJ (20.5) and Cu-Li (47.2Zr-47.2N) (5.6). By controlling the preparation process, the obtained samples have the effect of deformation-induced phase transition, that is, the effect of TRIP(Transformation-Induced plasticity. It is found that both amorphous alloy samples have excellent plastic deformation at room temperature and are accompanied by obvious strain hardening. The microstructure of the alloy is Ni-Nb- 尾 dendrite B2-Ni-Ti shape memory phase and amorphous matrix. The strain hardening behavior of the alloy is caused by the deformation within the grain and the induction of the multiple shear band, which inhibits the instability propagation of the single shear band and makes the alloy have a large plastic strain. By controlling the size of the sample, A rod-like Cutix (1.0mm / 1.5mm / 2.0mm / 2.5mm) rod-like composite material was successfully prepared. The composite consists of amorphous matrix and B2-CuZr martensite phase with diameter of about 200nm, and the amorphous composite is composed of amorphous matrix and B2-CuZr martensite with diameter of about 200nm. With the increase of B2 phase, the plastic deformation ability of the composites increased first and then decreased. When the sample diameter reached 1.5mm, the sample contained about 15%(vol)B2 phase. It has the highest compressive strength and 11.3% maximum plastic deformation, accompanied by obvious strain hardening. The results show that the phase transformation absorbs elastic strain energy, high density dislocation and clonic deformation in the plastic crystal phase. The stress concentration at the interface of amorphous / crystalline phase is the essential reason for the excellent mechanical deformation behavior of amorphous composites. In this study, two new amorphous composites were successfully fabricated by alloy composition design. Through the toughening of the second phase, the large plastic deformation ability and the obvious work hardening are obtained, and the high strength of the amorphous matrix is maintained, which lays a foundation for the toughening and further engineering application of the amorphous alloy.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8

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