2材料科学基础英文版课件_（四）.pptVIP

Effects of grain boundary segregation on the properties of materials Mechanical, corrosion, electrical, and magnetic properties * Results and discussion (3) R-square = 0.997 * Results and discussion (4) Temperature-time embrittlement diagram * Summary There is a linear relationship between DBTT and phosphorus boundary concentration. A temperature-time embrittlement diagram was established. From the diagram, the DBTT of the material aged for any time at any temperature can be predicted. * * Outline (1) Equilibrium grain boundary segregation Segregation of phosphorus and molybdenum Introduction, experiment, results and discussion, summary Relationship between phosphorus boundary concentration and ductile-to-brittle transition temperature (DBTT) Introduction, experiment, results and discussion, summary Effect of phosphorus grain boundary segregation on intergranular fracture Introduction, experiment, results and discussion, summary * Introduction (1) * Introduction (2) Does low temperature facilitate intergranular fracture? Christien’s results in 17-4 PH martensitic stainless steel: The specimen experienced ductile fracture, intergranular fracture, cleavage fracture when impact-fractured from 300oC to -196oC. (Christien, 2003) * Experiment Pretreated samples Experimental procedure Aging at different temperatures for different times and quenching Boundary concentration Fraction of Intergranular fracture SEM Impact test Machining DBTT Hardness test Metallographic analysis Hardness Microstructure, Grain size AES * Results and discussion (1) 480oC×1200h 650oC×2h Intergranular fracture is not observed at all test temperatures * Results and discussion (2) Stress Temperature O Intergranular fracture stress Cleavage fracture stress Yield strength Tc Ta Tb * Summary Phosphorus grain boundary segregation facilitates intergranular fracture. The specimen experienced ductile fracture, intergranular fracture, and cleavage fracture when impact-fractured from high to