Papers by Author: Yan Ping Miao

Abstract: Magnesium alloy is one of the most useful structural materials in the future. But the research report about surface strengthening of magnesium alloy is little in home and abroad. Ultrasonic impact strengthening treatment was carried out on AZ91D magnesium alloy, the change characteristics of surface microstructure was studied using SEM. The scratch hardness and wear-resistance were tested for both ultrasonic impact treatment and un-treated specimen using HRA-150 type Rockwell hardness tester and M-2000 model wear tester. The experimental results indicate that after ultrasonic impact, the grain boundary on the surfaces of AZ91D is obviously refined. When the ultrasonic impact time are 20 min, 30 min and 50 min, the scratch hardness on the surface of AZ91D increases 7.2%, 16.96% and 28.90%, respectively. For ultrasonic impact time of 50 min, the wear-resistance of treated specimen could be increased to 39.63% and 37.56% respectively for the wear time for 2 and 5 min. With increasing the ultrasonic impact time, the wear scar on the surface is become narrow. It is an effective method to increase the scratch hardness and wear-resistance of AZ91D magnesium alloy by using ultrasonic impact strengthening treatment.

Abstract: Porous TiC-Ni3Al performs were fabricated by using Ni, Al, Ti and graphite powder with self-propagating high-temperature combustion synthesis (SHS) method. Then, the porous perform were infiltrated with melt Ni3Al via the conventional pressureless infiltration process to prepare TiC/Ni3Al composites. Effects of the infiltration temperature and time on the microstructure, hardness and wear resistance of the composites were studied. XRD, SEM and EDS were used to analyze the phase identification and the solubility of Ni3Al and TiC in each other. The results show that pressureless melt infiltration is an effective method to fabricate dense TiC/Ni3Al composites. The infiltration time can greatly decrease when the infiltration temperature suitably increases. No obvious effect of the infiltration temperature and time on the hardness and the wear resistance of the composites were found. Ni3Al and TiC were well bonded, and they are the only two phases in the composites after infiltration. The wear resistance of TiC/Ni3Al composites including 70% and 80% TiC were promoted 3.25 and 4.33 times compared with pure Ni3Al, respectively.