摘要
通过在Gleeble 1500热模拟试验机上进行的单轴热压缩实验并结合SEM和EBSD分析技术,研究了共析钢在A_1—A_(r1)和A_1—A_(c1)温度范围内的两阶段变形对缓冷组织的影响。结果表明:共析钢在A_1—A_(r1)温度范围内进行过冷奥氏体形变后,在A_1—A_(c1)温度范围内再变形时,可以利用应变量控制再奥氏体化进程,在一定应变量下获得奥氏体与未溶渗碳体粒子的混合组织,在随后的缓冷过程中发生离异共析转变,获得超细化(α+θ)复相组织,其中α-Fe平均晶粒尺寸小于3μm,θ-Fe_3C粒子平均尺寸小于0.5μm。
For high carbon steels, the （a＋0） microduplex structure consisting of ultrafine ferrite matrix and dispersed cementite particles demonstrates a good balance between strength and ductility as compared with a normal microstructure, i.e., lamellar pearlite in eutectoid steel or lamellar pearlite plus pro-eutectoid cementite in hypereutectoid steel. The divorced eutectoid transformation （DET） has been confirmed to be very effective in ultrahigh carbon steels for the production of the （α＋θ） microduplex structure. In ultrahigh carbon steels, DET takes place during slow cooling of a mixing microstructure of austenite plus dispersed undissolved cementite particles formed by the intercritical annealing within the （α＋θ） two phase range. Due to the absence of the （α＋θ） two phase range, DET is difficult to take place in eutectoid steel. In the present work, DET was realized in eutectoid steel by a special thermal mechanical treatment, which involved two-stage hot deformation in the temperature ranges of Al to Arl and Al to At1 and subsequent slow cooling. The microstructure evolution during such treatment was studied by hot uniaxial compression tests using a Gleeble 1500 hot simulation test machine in combination with SEM and EBSD. The results indicate that during hot deformation in the temperature range of Al to Acl after hot deformation of undercooled austenite in the temperature range of Al to Ar1, the re-austenization could be controlled by the applied strain, leading to the formation of the mixing microstructure of austenite plus undissolved cementite particles at certain conditions. During subsequent slow cooling, DET took place, resulting in the formation of an ultrafine （α＋θ） microduplex structure with α-Fe grains less than 3μm and θ- Fe3C particles less than 0.5 #m.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第6期704-710,共7页
Acta Metallurgica Sinica
基金
新金属材料国家重点实验室资助项目
关键词
共析钢
离异共析转变
组织细化
奥氏体
应变量
eutectoid steel, divorced eutectoid transformation, microstructure refinement, austenite, strain
