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利用Gleeble3500试验机研究汽车用C-Mn-Al系TRIP钢的高温力学性能,测定了零塑性温度和零强度温度,应用差示扫描量热法测定其相变区间,采用扫描电镜和光学显微镜分析了不同拉伸温度对应的断口宏观形貌及断口附近组织组成.该钢种零塑性温度和零强度温度分别为1425℃和1430℃,第Ⅰ脆性区间为1400℃~熔点,第Ⅲ脆性区间为800~925℃.第Ⅲ脆性区脆化的原因是α铁素体从γ晶界析出,试样从975℃冷却至700℃过程中,随着α铁素体析出比例的增大,断面收缩率先减小后增大.基体α铁素体比例为8.1%时(850℃),断面收缩率降至28.9%;而拉伸温度在800℃以下时,基体α铁素体比例超过16.7%,断面收缩率回升至38.5%以上.该钢种在1275.6℃时开始析出少量粗大的Al N颗粒,但对钢的热塑性没有影响.
The mechanical properties of C-Mn-Al TRIP steels for automotive applications were investigated by Gleeble 3500 testing machine. The zero-plastid temperature and the zero-intensity temperature were measured. The phase transitions were determined by differential scanning calorimetry. Scanning electron microscopy and optical microscopy The macroscopic morphology of the fractures and the microstructure of the fractures near the fractures were observed under different stretching temperatures.The zero-plasticity temperature and zero-intensity temperature of the steel were 1425 ℃ and 1430 ℃ respectively, the first fragile zone was 1400 ℃ ~ the melting point, the third fragile zone was 800 to 925 ° C. The reason for the embrittlement of the third brittle zone is that the α ferrite is precipitated from the γ grain boundary. When the sample is cooled from 975 ° C. to 700 ° C., the cross-section shrinks as the proportion of α ferrite precipitates increases After the first α-ferrite ratio is 8.1% (850 ℃), the cross-sectional shrinkage decreases to 28.9%. When the tensile temperature is below 800 ℃, the ratio of matrix α ferrite is over 16.7% The shrinkage rate of the section rose to more than 38.5% .The steel began to precipitate a small amount of coarse Al N particles at 1275.6 ℃, but had no effect on the thermoplasticity of the steel.