材料期刊网

The retained strength and hardness of Ti3AlC2 bars quenched from 200 to 1300 degrees C in air, water and silicon oil were investigated to probe the thermal shock resistance of Ti3AlC2 in various media. The measured retained strength displayed different trends for the samples quenched in various media. For the samples quenched in air, the retained strength showed somewhat enhancement with increase of the temperature difference. For the samples quenched in water, the retained strength exhibited a complex evolution and could be divided into four zones, i.e., (i) no damage zone (20-300 degrees C), (ii) strength degradation zone (300-500 degrees C), (iii) stable strength zone (500-1000 degrees C), and (iv) strength enhancement zone (1000-1300 degrees C). Therefore, the minimum retained strength in the third zone, which is higher than 60% of the initial strength, provided a prediction that the strength loss by thermal shock for Ti3AlC2 should be less than 40%. SEM analysis revealed that an oxide scale of alpha-Al2O3 was formed at high temperature for which the residual stress was calculated. The strength degradation in the second temperature zone was imputed to the weakening of grain boundaries caused by water infiltration, whereas the strength enhancements for the air-quenched samples in the fourth zone was attributed to the formation of oxide scale and the residual compressive stresses in the oxide layer. The damage caused by quenching in oil for this ceramic was demonstrated between that of air and water quenching. Finite element method (FEM) was used to simulate the failure in bending, and the results indicated that the strength of the sample with an oxide scale was about 5-10% higher than that of homogeneous sample. (c) 2004 Elsevier Ltd. All rights reserved.