Papers by Author: Mohammad Hossein Enayati

Abstract: An ultrafine grained 304L stainless steel with average grain size of 650±100 nm was produced by a combination of cold rolling and annealing. Wear behavior of the steel was examined by dry sliding wear tests under different loads. Different microstructural characterizations were conducted on the ultrafine grained structure after thermomechanical processing and wear tests. The results demonstrated that the steel had yield strength of 720 MPa and total elongation of 47%, which is almost twice higher than typical coarse grained strength. Also, wear tests results showed a good linear relation between the cumulative wear loss and distance in each normal load. Wear rate was about 0.024, 0.043 and 0.093 mg/m for normal loads of 10, 20 and 30N, respectively. Wear mechanism was also recognized as delamination (in the early stage) and mixture of delamination and abrasion in higher distances.

Abstract: In this research, the formation mechanisms of a (NiCr)Al-Al2O3 nanocomposite were investigated. The structural changes of powder particles during mechanical alloying were studied by X-ray difractometry (XRD) and the morphology and cross sectional microstructure of powder particles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The methodology involved mechanical alloying of NiO, Cr, and Al with molar ratios of 3:3:8. During mechanical alloying, NiO was first quickly reduced by aluminum atoms to produce NiAl nanocrystalline and Al2O3. Subsequently, and when a longer milling time was applied, chromium atoms diffused into the NiAl lattice. The heat treatment of this structure led to the formation of the (NiCr)Al intermetallic compound as well as Al2O3 with crystalline sizes of 23 nm and 58 nm, respectively.