摘要
将30MnB5热成形钢采用淬火+回火处理,利用电子背散射衍射(EBSD)技术研究了淬火态和不同温度回火后马氏体变体与母相的取向关系及其取向差变化,采用单个原奥氏体晶粒区域做出的马氏体{100}极图,并结合等密度线极图的方法对马氏体变体与母相的取向关系进行了判定.结果表明,30MnB5热成形钢淬火后得到的马氏体变体与母相的取向关系更接近N-W关系,实际极点分布在理论极点周围,并且经不同温度回火后,马氏体变体与母相的取向关系没有明显改变,但变体数目有减少的趋势.淬火态和不同温度回火后马氏体变体的取向差都主要分布在5°以下和50°以上,随着回火温度的升高,小于5°的小角度晶界略微减少,但仍占较高的比例,而大于50°的大角度晶界则呈上升趋势.这些小于5°的小角度晶界主要存在于马氏体变体内部,源自马氏体板条间的取向差,是导致不同马氏体变体间的角度离散分布在理论值周围的主要原因.
Currently, the senior-level hot stamping steels, such as 30MnB5, could not be used widely in automotive body like 22MnB5 hot stamping steel due to its low plasticity and high hydrogen induced cracking sensitivity after hot stamping. However, its good mechanical properties after tempering processes made it suitable for automotive structural parts. In this paper, the 30MnB5 hot stamping steel was quenched and tempered at 200-600 E for 2 rain. The orientation relationship （OR） with parent phase and misorientation evolution of martensite variants were characterized by EBSD. The OR between martensite variants and parent phase was determined by using {100} pole figure of martensite variants inside a single prior austenite grain and the method of pole figure contouring. The results showed that, the OR between martensite variants and parent phase in 30MnB5 hot stamping steel after quenching was closer to N-W OR than K-S OR, and the actual pole points were distributed around the theoretical pole points. The OR between martensite and parent phase variants did not change in the samples tempered at different temperatures for 2 min, but the number of martensite variants inside a single prior austenite grain tended to decrease. The misorientation of martensite variants after quenched and tempered at different temperatures were both mainly distributed in the angle range of less than 5° and more than 50°. As tempering temperature increased, the low angle grain boundaries below 5° were decreased slightly while the high angle grain boundaries above 50° reflected an upward trend, but the former still accounted for a large percentage. These low angle grain boundaries below 5°, mainly existing inside martensite variants andderived fl＇om the misorientation between martensite laths, were the main retzson tlmt led to discrete distribution of angles between different martensite variants around theoretica.1 values.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第2期137-145,共9页
Acta Metallurgica Sinica
基金
高等学校博士学科点专项科研基金资助项目20110006110007~~
