Shouxin Li

A SIMPLE-MODEL FOR THE REFINEMENT OF NANOCRYSTALLINE GRAIN-SIZE DURING BALL MILLING

acad sinica,inst met res,state key lab rapid solidifcat nonequilibrium alloys,shenyang 110015,peoples r china.;li, sx (reprint author), acad sinica,inst met res,state rey lab fatigue & fracture mat,shenyang 110015,peoples r china

A model of Hall-Petch relationship in nanocrystalline materials

In this paper, a new model of Hall-Petch (HP) relationship in nanocrystalline materials is proposed. The normal HP relationship is well described by a grain boundary dislocation source model. The transition from normal to abnormal HP relationship occurs at the point where grain size is smaller than the average spacing between the grain boundary sources. The abnormal HP relationship can be expressed as Hv−Hm = β 1−3δeffd where Hv, Hm are the hardness of the nanocrystalline and amorphous state of the material, respectively. δeff is the effective grain boundary thickness: d is the grain size of teh nanocrystalline material and β is a constant. The distribution of grain sizes plays an essential role in the transition region.

The Paris law in metals and ceramics

In this letter, an ideal model about Paris law is proposed. This model may play some role in analysing the experimental data and exploring their related mechanisms.

Thermal residual stress relaxation at surface of SiC/Al composite

Thermal residual stresses in the bulk and near the surface of a SiC/Al composite are calculated through the two-dimensional finite-element method (FEM). With regards to material constitutive relations, a thermal elastic-plastic isotropic material and isotropic thermal-elastic models are selected for Al and SiC, respectively. A close correlation in the thermal residual stress between FEM calculations and X-ray diffraction measurements is indicated, and the effect of thermal residual stress relaxation near the surface on bulk residual stresses in the composite is discussed. 9 refs.

Preparation of nanocrystalline CuTi by quenching the melt under high pressure

Abstract A new method of preparing a bulk nanocrystalline alloy by means of quenching a melt under high pressure has been developed. Using this method, a bulk CuTi alloy with 10–20 nm crystallites was synthesized. The structures and grain sizes of the alloy were examined by means of X-ray diffraction and TEM. We know of no precedent for using this method to directly prepare nanocrystalline alloys. The interfaces within the bulk alloys are very clean, and there is no porosity. The mechanism for nanometer-sized crystallite formation by this method is discussed.

A GEOMETRIC MODEL FOR FATIGUE CRACK CLOSURE INDUCED BY FRACTURE SURFACE-ROUGHNESS UNDER MODE-I DISPLACEMENTS

A geometric model dealing with the roughness-induced fatigue crack closure under mode I displacements is proposed. It is shown that roughness-induced crack closure can also be acquired without mode II and III displacements at the crack tip. In this mechanism, the severe contact region is near the crack tip. The average crack closure ratio is the result of discrete asperities which come into contact.

Stress carrying capability and interface fracture toughness in SiC/6061 Al model materials

Abstracts are not published in this journal

STRESS-DISTRIBUTION IN SIC(P)-AL COMPOSITE WITH INTERPHASE

ACAD SINICA,INST COMP TECHNOL,CAD CAM TECHNOL ADV MFG LAB,SHENYANG 110003,PEOPLES R CHINA.;LI, SX (reprint author), ACAD SINICA,INST MET RES,STATE KEY LAB FATIGUE & FRACTURE MAT,SHENYANG 110015,PEOPLES R CHINA

Preparation of CuSi bulk nanometre alloy under high pressure

Abstract A CuSi bulk nanocrystalline material was prepared by quenching of the melted Cu70Si30 alloy at a cooling rate of 200 K s−1 under 6 GPa. It was found that the nanocrystalline consists of γ-Cu5Si and an unknown phase. The study on the crystal structure and thermal stability of the unknown phase was carried out. The formation mechanism of bulk nanocrystalline material under high pressure was discussed.

Heating of metal/ceramic foils in an electron microscope

acad sinica,inst comp technol,cad cam technol adv mfg lab,shenyang 110003,peoples r china.;li, sx (reprint author), acad sinica,inst met res,state key lab fatigue & fracture mat,shenyang 110015,peoples r china