激光喷丸对块体非晶合金微观结构及性能的影响

发布时间：2018-05-31 01:19

本文选题：激光喷丸 + vit1块体非晶合金　；参考：《山东大学》2016年博士论文

【摘要】：非晶合金由于具有高耐磨、耐蚀性、高弹性极限、高强度以及优良的磁性能等优点,因而在多种领域均具有十分广阔的应用前景。然而,非晶合金由于其独特的短程有序、长程无序结构,致使其在室温下的宏观塑性近乎为零,成为制约其成形制造以及的工程应用关键瓶颈。因此,如何改善非晶合金的室温塑性已经成为材料研究领域迫切需要解决的问题。本文实验采用Zr41.2Ti13.8Cu12.5Ni10Be22.5(vit1)块体非晶合金,开展了激光喷丸热效应、激光喷丸冲击力效应,以及激光喷丸热/力效应对非晶合金表面形貌、微观组织结构以及力学性能和耐腐蚀性的影响等研究工作。主要结论如下：(1)首先研究了热效应为主的单点激光喷丸对非晶合金表面形貌的影响,探讨了激光与非晶合金相互作用的过程和机理,通过表面张力波理论、Kelvin.Helmholtz不稳定性机制以及Saffman-Taylor不稳定性理论对喷丸边缘区域形成的的周期性波纹以及指化现象进行了理论解释；其次研究了圆环结构直径和波纹间距随激光能量、脉冲次数的演变情况。研究结果表明,圆环结构的直径随着激光能量和脉冲次数的增加近似呈线性增大,但脉冲次数大于10后圆环结构的直径增长趋势放缓。波纹间距不随激光能量的大小而改变,但随着脉冲次数的增加逐渐增大。当能量为600 mJ,脉冲次数为200时,在喷丸区域还形成大量无规则分布的微裂纹。(2)系统研究了冲击力效应为主的单点激光喷丸对非晶合金表面完整性的影响。首先研究了激光喷丸对非晶合金表面微观组织结构、光学形貌和粗糙度的影响,并对其影响机制进行了分析；其次研究了激光喷丸对非晶合金硬度的影响,分析了硬度变化的原因；最后对激光喷丸后非晶合金的表面微裂纹/剪切带及其形成机制进行了分析。研究结果表明,非晶合金在激光喷丸处理后仍然保持了非晶态结构,但喷丸区域形成一个圆形微凹坑,且表面粗糙度增大,原因在于激光喷丸时形成的冲击波压力远高于材料弹性极限,并且激光能量不均和吸收层表面的不平整,造成冲击波压力不均匀。随着喷丸过程中激光能量的增加,非晶合金表面微凹坑的直径和深度也呈现出逐渐增大的趋势,同时表面粗糙度也越高。激光喷丸区域硬度降低,且喷丸中心区域硬度减小幅度最大,约为13%,分析表明激光喷丸塑性变形区域内形成的大量剪切,由于应变软化导致非晶合金硬度降低。在激光喷丸诱导的高压冲击波作用下,非晶合金试样表面的剪切带／微裂纹是通过孔洞的连接来实现的。(3)系统研究了多点激光喷丸对非晶合金微观组织结构和力学性能的影响规律。首先分析了等腰直角搭界方式下不同横向搭接率对非晶合金表面粗糙度的影响；其次,采用优化的工艺参数对非晶合金进行激光喷丸处理,研究了激光喷丸前后非晶合金微观组织结构的变化；最后通过三点弯曲实验、单向压缩实验系统研究了激光喷丸对非晶合金室温塑性的影响。研究结果表明,当横向搭接率为29.3%时,激光喷丸后试样表面粗糙度最小。多点激光喷丸后,非晶合金仍然保持非晶态结构,但在非晶合金内产生了大量的自由体积。激光喷丸处理后非晶合金在三点弯曲过程中塑性变形挠度增大了1.83倍,分析表明塑性的增强得益于激光喷丸后非晶合金自由体积的增大,在后续变形中更易生成多重剪切带。单向压缩实验表明激光喷丸非晶试样具有明显的尺寸效应,小尺寸块体非晶合金试样具有更高的压缩强度和更优异的塑性。(4)系统研究了多点激光喷丸热/力效应对非晶合金微观组织结构和性能的影响。首先通过无吸收层激光喷丸(Laser shock peening without coating, LSPwC)工艺对非晶合金试样表面进行喷丸处理,并对LSPwC处理后非晶合金表面的微观组织结构进行了分析；其次研究了LSPwC处理后非晶合金的室温塑性；分析了激光喷丸热/力效应对非晶合金塑性影响的机制；最后研究了LSPwC处理后非晶合金的纳米硬度和耐蚀性。研究结果表明,LSPwC处理后非晶合金表面仍保持非晶特质,但在非晶合金熔融表层120μm以下检测到分布均匀的晶化相。LSPwC处理后非晶合金塑性挠度增加了23%,分析表明在弯曲变形过程由LSPwC引起的非晶合金自由体积的增大、晶化相的产生以及表层复杂分布的残余应力使得非晶合金的塑性增大,由LSPwC处理后产生的烧蚀坑导致非晶合金的塑性降低,但其对LSPwC处理后非晶合金塑性的影响并不占据主导地位。LSPwC处理后非晶合金纳米硬度减小,但耐蚀性增强,并且采用吸收层的激光喷丸处理后的非晶合金耐蚀性更好。
[Abstract]:Because of its advantages of high abrasion resistance, corrosion resistance, high elasticity limit, high strength and excellent magnetic properties, amorphous alloys have a very broad application prospect in many fields. However, because of their unique short range order and long range disordered structure, the macroscopic plasticity at room temperature is almost zero, which restricts its formation. It is a key bottleneck in the engineering application of shape manufacturing and engineering. Therefore, how to improve the room temperature plasticity of amorphous alloys has become an urgent problem to be solved in the field of material research. In this paper, Zr41.2Ti13.8Cu12.5Ni10Be22.5 (vit1) bulk amorphous alloy was used to carry out the thermal effect of laser shot peening, the impact force effect of laser shot peening, and the laser shot peening heat. The main conclusions are as follows: (1) first, the effect of the single point laser shot peening on the surface morphology of amorphous alloy was first studied, and the process and mechanism of the interaction between laser and amorphous alloy were discussed. The Zhang Libo theory, the Kelvin.Helmholtz instability mechanism and the Saffman-Taylor instability theory explain the periodic ripples and the denying phenomena in the edge region of the shot peening. Secondly, the evolution of the ring structure diameter and the ripple spacing with the laser energy and the pulse number are studied. The diameter of the structure increases linearly with the increase of the laser energy and the number of pulses, but the growth trend of the ring structure is slowed down after the number of pulses is greater than 10. The wave spacing does not change with the size of the laser energy, but increases with the increase of the number of pulses. When the energy is 600 mJ and the number of pulses is 200, it is also formed in the shot peening area. A large number of irregular microcracks. (2) the effect of single point laser shot peening on the surface integrity of amorphous alloy was studied systematically. First, the effect of laser shot peening on the microstructure, optical morphology and roughness of amorphous alloy surface was studied, and the mechanism of its effect was analyzed. Secondly, the laser spray was studied. The influence of the pill on the hardness of amorphous alloy was analyzed, and the reasons for the change of hardness were analyzed. Finally, the surface micro crack / shear band and the formation mechanism of the amorphous alloy after the laser shot peening were analyzed. The results showed that the amorphous alloy still retained the amorphous structure after the laser shot peening, but the shot peening area formed a circular micropits. The surface roughness increases because the shock wave pressure formed by the laser shot peening is much higher than the elastic limit of the material, and the uneven laser energy and the surface of the absorption layer make the shock wave pressure uneven. With the increase of the laser energy in the shot peening, the diameter and depth of the surface micro pits of the amorphous alloy surface also increase gradually. At the same time the surface roughness is also higher. The hardness of the laser shot peening area decreases and the hardness of the shot peening center is reduced to about 13%. The analysis shows that a large amount of shear formed in the plastic deformation region of the laser shot peening is caused by the strain softening. The shear band / micro crack on the surface of the alloy sample is realized through the connection of holes. (3) the influence of multi point laser shot peening on the microstructure and mechanical properties of amorphous alloy is systematically studied. First, the influence of different transverse lap ratio on the surface roughness of amorphous alloy under the isosceles right angle lap mode is analyzed. Secondly, the application of the method is to analyze the influence of the different transverse lap ratio on the surface roughness of the amorphous alloy. The optimized process parameters of the amorphous alloy were treated by laser shot peening, and the microstructure of the amorphous alloy before and after the laser shot peening was studied. Finally, the effect of laser shot peening on the room temperature plasticity of amorphous alloy was studied by three point bending experiment and unidirectional compression experimental system. The results showed that when the transverse lap rate was 29.3%, laser After shot peening, the surface roughness of the sample is minimal. After the shot peening, the amorphous alloy remains amorphous, but a large amount of free volume is produced in the amorphous alloy. The deformation deflection of the amorphous alloy after the laser shot peening is 1.83 times higher than that of the three point bending process. The analysis shows that the plasticity is enhanced by the laser shot peening. The increase of the free volume of the crystalline alloy makes it easier to produce multiple shear bands in the subsequent deformation. The unidirectional compression test shows that the amorphous samples of the laser shot peening have obvious size effect, and the small size bulk amorphous alloy samples have higher compressive strength and more excellent plasticity. (4) the thermal / force effect of multi point laser shot peening on the amorphous alloy has been studied systematically. The influence of microstructure and properties of the amorphous alloy was first shot by Laser shock peening without coating (LSPwC) technology, and the microstructure of the amorphous alloy surface after LSPwC treatment was analyzed. Secondly, the room temperature plasticity of the amorphous alloy after LSPwC treatment was studied. The mechanism of the effect of laser shot peening heat / force on the plasticity of amorphous alloy was analyzed. The nano hardness and corrosion resistance of the amorphous alloy after LSPwC treatment were studied. The results showed that the amorphous alloy remained amorphous on the surface of the amorphous alloy after LSPwC treatment, but the homogeneous crystalline phase.LS was detected below 120 u m in the melt surface of the amorphous alloy. The plastic deflection of amorphous alloy after PwC treatment increased by 23%. The analysis showed that the free volume of amorphous alloy increased by LSPwC, the production of crystalline phase and the residual stress in the complex surface of the surface made the plasticity of amorphous alloy increase, and the ablative pit produced by the LSPwC treatment resulted in the reduction of the plasticity of amorphous alloy, but it also resulted in the reduction of the plasticity of amorphous alloy. The effect of LSPwC treatment on the plastic properties of amorphous alloys does not occupy the dominant position of.LSPwC treatment, the hardness of amorphous alloy decreases, but the corrosion resistance is enhanced, and the corrosion resistance of amorphous alloy after the laser shot peening treatment is better.
【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG139.8;TG668

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