热轧TC4合金电脉冲热处理工艺研究

发布时间：2018-04-04 12:05

本文选题：钛合金　切入点：电脉冲热处理　出处：《北京理工大学》2015年硕士论文

【摘要】：钛合金具有密度小、比强度、抗腐蚀性能好等诸多优异性能，是较为理想的轻质装甲金属材料。有研究表明，在防护性能相同的情况下，钛合金装甲的重量比装甲钢轻25%。然而，钛合金是一种高绝热剪切敏感性的材料，在高速变形过程中极易以绝热剪切的形式失效，严重限制了它在装甲防护领域的应用。针对以上问题，本文以热轧Ti-6Al-4V合金（简称为TC4合金）为研究对象，以降低其绝热剪切敏感性为研究目标，采用特殊电脉冲热处理的方法，对热轧TC4合金的微观组织细节特征进行调控，系统地研究了电脉冲热处理对热轧双态TC4合金和热轧等轴TC4合金微观组织和力学性能的影响规律及机理。得出如下主要结论：电脉冲热处理可以使热轧TC4合金的组织在数分钟内转变成魏氏组织，且热处理温度越高，转变成魏氏组织所需要的保温时间越短；组织转变成魏氏特征之前，原始热轧组织仅发生再结晶；转变成魏氏组织之后，β晶粒和片层宽度随着热处理温度的上升和保温时间的延长而增大。热轧双态组织TC4合金经电脉冲热处理后，，仅发生再结晶而未发生魏氏转变的组织其准静态压缩塑性显著提高，且破坏强度也随之提高；而一旦组织转变成魏氏组织，其临界失效应变显著降低，最终的破坏强度也呈现降低的趋势。热轧等轴组织TC4合金经电脉冲热处理后，准静态压缩塑性显著提高，但强度略有降低；刚刚完成组织转变、具有较细晶粒的魏氏组织合金具有最大的准静态临界失效应变。电脉冲热处理可以显著提高热轧TC4合金的动态临界破坏应变值和发生剪切破坏前的单位体积吸收功，即可以显著提高材料的抗绝热剪切破坏能力，但对动态强度未产生明显影响。热轧双态组织TC4合金经800℃/20min电脉冲处理后临界剪切破坏应变值比原始热轧钛合金提高了76.6%，绝热剪切破坏前的材料单位体积吸收功提高了75.8%。热轧等轴组织TC4合金经1000℃/5min电脉冲处理后临界剪切破坏应变值相比原始热轧TC4合金提高了133%，单位体积吸收功提高了192%。在动态加载条件下，绝热剪切带在电脉冲热处理后转变成的魏氏组织中扩展时出现分叉现象，扩展路径变得更加曲折；且在主剪切带周围组织中发现均匀变形区，消耗了大量的冲击功，推迟了裂纹的萌生和扩展，因此电脉冲热处理后发生魏氏组织转变的合金动态塑性显著增强，绝热剪切敏感性显著降低。
[Abstract]:Titanium alloy has small density, specific strength, good corrosion resistance and other excellent properties, is an ideal light armored metal materials. Studies have shown that the protection performance under the same weight of titanium alloy armor than light armor steel 25%. however, titanium alloy is a kind of high adiabatic shear sensitivity of materials. Easy to form adiabatic shear failure in the deformation process of high speed, seriously limit its application in armor protection field. To solve the above problems, based on the hot rolled Ti-6Al-4V alloy (TC4 alloy) as the research object, in order to reduce the adiabatic shear sensitivity as the research object, using the method of special electric pulse heat treatment, microstructure detailed microstructure characteristics of the hot rolled TC4 alloy to control, systematically studied the electric pulse heat treatment on the microstructure and mechanical hot rolled dual phase TC4 alloy hot rolling shaft and properties of TC4 alloy and the influence law of the mechanism. The main conclusions are as follows:
Electric pulse heat treatment can improve the microstructure of the TC4 alloy hot rolled into widmanstatten structure in a few minutes, and the higher the temperature, into the widmanstatten structure required shorter holding time; before the organization into widmanstatten characteristics, original microstructure occurs only after recrystallization; into widmanstatten structure, grain and film layer width increases with the increase of heat treatment temperature and holding time.
Hot rolled duplex microstructure of TC4 alloy by electric pulse after heat treatment, only the recrystallization and not change the Widmanstaten quasi-static compressive plasticity increased significantly, and the failure strength was increased; and once the organization turned into widmanstatten structure, the critical failure strain decreased significantly, the ultimate failure strength also decreased hot rolled equiaxed microstructure of TC4 alloy by electric pulse after heat treatment, the quasi-static compression plastic significantly improved, but the strength decreased slightly; just completed the transformation, has a fine grain widmanstatten alloy has the largest quasi static critical failure strain. The electric pulse heat treatment can significantly improve the dynamic critical failure strain of hot rolled TC4 alloy and the shear failure occurred before the unit volume of absorbing received power, which can obviously improve the anti adiabatic shear damage ability, but did not have a significant effect on the dynamic strength of hot rolled dual state. The microstructure of TC4 alloy by 800 DEG /20min after electric pulse treatment of critical shear strain value than the original hot rolled titanium alloy is increased by 76.6%, the adiabatic shear failure before the unit volume of material absorption power is increased by 75.8%. hot equiaxed microstructure of TC4 alloy by 1000 DEG /5min after electric pulse treatment of critical shear strain values compared to the original hot rolling TC4 alloy increased 133%, the unit volume power absorption increased by 192%.
Under dynamic loading, the adiabatic shear band bifurcation phenomena in electric pulse expansion after heat treatment into the widmanstatten structure when the propagation path becomes more tortuous; and in the main shear zone found uniform deformation zone in the surrounding tissue, consumes a large amount of impact energy, delayed the initiation and propagation of crack, dynamic alloy so the electric pulse heat treatment after widmanstatten microstructure plastic significantly enhanced adiabatic shear sensitivity significantly reduced.

【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG337.6

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