Investigation on Microstructure and Microhardness of Adiabatic Shear Band of Saw-tooth Chip in Machining TC4 Alloy

Abstract

Abstract:

Microstructure of ASB of saw-tooth chip produced in different cutting speeds was observed and analyzed by optical microscope and TEM in machining of TC4 alloy. The microhardness of ASB was also measured. Experimental results show that ASB formed at low cutting speed is deformed band, at higher cutting speed, ASB becomes transformed band composed of fine equiaxed grains and martensitic phase that comes from phase transformation β→α″. With the further increase of cutting speed, amorphization that had not been observed before occurence inside ASB. The microhardness of ASB always increases with the increasing of cutting speed whatever the ASB is deformed or transfromed band. According to the law of microstructure evolution and the increase of microhardness of ASB, the microhardness increase can be divided into three stages: strain-hardening, grain refining and martensitic phase transformation hardening, amorphization hardening.
saw-tooth chip; adiabatic shear band(ASB); titanium alloy; martensitic phase transformation; transmission electron microscope(TEM) analysis

摘要：

使用金相显微镜、透射电子显微镜观察了TC4钛合金在不同切削速度下形成的锯齿形切屑的绝热剪切带的微观组织形貌,测量了绝热剪切带的显微硬度。结果表明,在较低切削速度下,绝热剪切带为形变带;在较高切削速度下,绝热剪切带为由细小等轴晶粒和局部发生了β相转变为α″相的马氏体相组成的转变带;随着切削速度的进一步提高,在绝热剪切带中观察到了非晶化这一新现象。无论绝热剪切带是形变带还是转变带,其显微硬度都随切削速度的增大而增大。根据绝热剪切带微观组织和显微硬度的变化规律,绝热剪切带显微硬度的强化可分为三个阶段：形变强化、细晶和马氏体相变强化、非晶强化。

关键词: 锯齿形切屑, 绝热剪切带, 钛合金, 马氏体相变, 透射电子显微分析

CLC Number:

TG506.2

WANG Sheng-Beng. Investigation on Microstructure and Microhardness of Adiabatic Shear Band of Saw-tooth Chip in Machining TC4 Alloy[J]. China Mechanical Engineering, 2012, 23(9): 1117-1121.

王升平. TC4钛合金锯齿形切屑绝热剪切带的微观组织和显微硬度变化[J]. 中国机械工程, 2012, 23(9): 1117-1121.

References

[1]杨扬[1],程信林[1],李正华[2],莫文剑[1],高文柱[2],裴大荣[2].冶金因素影响绝热剪切带形成的金相观察[J].稀有金属材料与工程,2003,32(4):261-263.
[2]段春争[1],王敏杰[1],庞俊忠[1,2],李国和[1].高强度钢正交切削过程中剪切变形局部化研究[J].大连理工大学学报,2006,46(3):355-360.
[3]杨勇[1],柯映林[1],董辉跃[1].钛合金切削绝热剪切带形成过程的有限元分析[J].浙江大学学报：工学版,2008,42(3):534-538.
[4]汪冰峰[1],杨扬[1].钛合金TC16中绝热剪切带的微观结构演化[J].中国有色金属学报,2007,17(11):1767-1772.
[5]王敏杰[1],段春争[1],刘洪波[1].正交切削切屑形成中绝热剪切行为的实验研究[J].中国机械工程,2004,15(18):1603-1606.
[6]John Barry Gerald Byrne . The Mechanisms of Chip Formation in Machining Hardened Steels [J]. 2002,3(3) .
[7]Yang Yang Wang B F . Dynamic Recrystallization in Adiabatic Shear Band in a-titanium [J]. 2006,60(17/18) .
[8]YANG Yang XIONG Jun YANG Xu-yue . Microstructure evolution mechanism in adiabatic shear band in TA2 [J]. 2004,4(4) .
[9]Yang Y Li J F . Study on Mechanism of Chip For-mation During High-speed Milling of Alloy Cast Iron [J]. 2010,46(1/4) .
[10]杨扬 [1],熊俊 [1],杨续跃 [2].Microstructure evolution mechanism in adiabatic shear band in TA2[J].中国有色金属学会会刊：英文版,2004,14(4):670-674.
[11]Cotterell M Byrne G . Dynamics of Chip Formation During Orthogonal Cutting of Titanium Alloy Ti-6AI-4V [J]. 2008,57(01) .
[12]S. Sun M. Brandt M. S. Dargusch . Characteristics of cutting forces and chip formation in machining of titanium alloys [J]. 2009,7/8(7/8) .
[13]Gente A Hoffmeiste H W . Chip Formation in Ma- chining Ti6A14V at Extremely High Cutting Speeds [J]. 2001,50(01) .
[14]Velasquez J D P Bolle B Chevrier P . Metal-lurgical Study on Chips Obtained by High Speed Machining ofaTi-6 wt.%A1-4 wt.%VAlloy [J]. 2007,452/453 .
[15]Bayoumi AE. Xie JQ. . SOME METALLURGICAL ASPECTS OF CHIP FORMATION IN CUTTING TI-6WT-PERCENT-AL-4WT-PERCENT-V ALLOY [J]. 1995,1/2(1/2) .
[16]C.Z. Duan M.J. Wang . Characteristics of adiabatic shear bands in the orthogonal, cutting of 30CrNi_3Mo V steel [J]. 2005,1(1) .