石墨化碳钢室温压缩变形过程的试验研究

Experimental Research on Compressive Deformation Process of Graphitized Carbon Steel at Room Temperature

利用Gleeble-3500热模拟试验机对以铁素体+石墨为组织特征的石墨化碳钢进行了室温压缩变形试验。采用金相显微镜研究了应变速率(0.01、0.1、1s^-1)对钢的变形行为及组织演变特征的影响。结果表明:试验范围内应变速率对试验钢的压缩变形行为影响不大,即表现为在位移小于6.5mm(对应压下量54.2%)的压缩过程中,不同应变速率下的压缩载荷均随着位移的增加而稳定增大,压缩试样的鼓度在6.5mm位移处达到最大值;而在位移大于6.5mm的压缩过程中,压缩载荷急剧增大,压缩试样的鼓度逐渐减小,研究认为这是此阶段压缩试样端面径向伸长率的急剧增大引起的。另外,在不同应变速率下的压缩变形过程中,试样的3个不均匀变形区(大变形区、自由变形区和难变形区)中的石墨粒子的变形量总大于铁素体基体的变形量,这是由简单六方晶体结构的石墨层与层之间易滑动所致。

Compression deformation of graphitized carbon steel with microstructure consisting of ferrite and graphite was carried out by a Gleeble-3500 thermal simulation tester at room temperature.The effect of strain rate(0.01,0.1,1 s^-1)on deformation behavior and microstructure evolution of the steel was studied by metallographic microscope.The test results showed that the strain rate in the test range had a little effect on the compressive deformation behavior of the test steel,i.e.,in the compression process with displacement less than 6.5 mm(corresponding to the reduction of 54.2%),the compression load at different strain rates increased steadily with the increase of displacement,and the crowning value of the compressed sample reacheded the maxmim at a displacement of 6.5 mm;in the compression process with displacement greater than 6.5 mm,the compression load increased rapidly and the crowning value decreased gradually,which was believed that this is caused by the sharp increase in the radial elongation of the end face of the compressed sample at this stage.In addition,during the compression deformation process at different strain rates,the micro-deformation degree of graphite particles was always greater than that of ferritic matrix in the three inhomogeneous deformation zones(large deformation zones,free deformation zones and difficultly deformed zones),which stemmed from easy slipping between graphite layers with a simple hesagonal crystal structure.