Songsong Xu

Influence of Austenitizing Temperature and Time on Microstructure and Mechanical Properties of an YP460 Grade Crack Arrest Steel

The influence of austenitizing temperature and austenitizing holding time on the microstructure and mechanical properties of a YP460 grade crack arrest steel was investigated. The first group specimens were austenitized at several temperatures ranging from 900 to 950 °C followed by water cooling. The second group specimens were austenitized at 900 °C with austenitizing holding time from 0.25 to 5 h followed by water cooling. Microstructure was characterized through optical microscopy. Tensile properties, hardness and plane strain fracture toughness of all these materials were determined and correlated with the microstructure. The results indicated that the austenitizing temperature influences the volume fraction of bainite and ferrite and then the mechanical properties. The volume fraction of bainite and ferrite and grain size are also affected by austenitizing time.

Effects of Matrix Microstructure on the Nanoscale Precipitation and Precipitation Strengthening in an Ultra-high Strength Steel

Matrix microstructure and nanoscale clusters are the two main factors influencing the mechanical properties of nanocluster strengthened steels. Here, an ultra-high strength steel with a tensile strength of ~1.64 GPa and an elongation of ~14% has been developed through a combination of fine matrix microstructure and precipitation strengthening. Matrix microstructure was primarily controlled by annealing treatment. After annealing treatment at 750 °C for 1 h, the hot-rolled microstructure changes to the layered sorbite-like structure. The precipitation strengthening contributes a similar yield strength of ~494 MPa in both hot-rolled and annealed steels. The results indicate that there is no effect of matrix microstructure on the subsequent precipitation of nanoscale clusters and precipitation strengthening. The matrix microstructure and the precipitation of nanoscale clusters are independent and can be controlled separately.

Effects of Ce Addition on the Microstructure and Mechanical Properties of Accident-Tolerance Fe-Cr-Al Fuel Cladding Materials

Fe-Cr-Al alloys are promising materials for accident-tolerance fuel cladding applications due to their excellent performance of oxidation and corrosion resistance under elevated temperature. In this study, effects of the addition of a small neutron absorption cross section rare-earth element Cerium (Ce) on the microstructure and mechanical properties of Fe-Cr-Al alloys with 0–0.1 wt% Ce have been investigated. As Ce content increased, the grains became size-refining obviously and number of precipitates increased. The results of EDS showed that the precipitates were mainly consisted of intermetallic compounds. Notably, the ultimate tensile strength and elongation reached the optimized values when the content of Ce was 0.02 wt%. However, the tensile properties decreased when Ce content was above 0.05 wt%, which may be due to the excess of intermetallic compounds.

Influence of Hot Rolling on Mechanical Behavior and Strengthening Mechanism in Boron Carbide Reinforced Aluminum Matrix Composites

Boron carbide reinforced aluminum matrix composites are widely used as neutron absorption materials. Here we report that mechanical alloying has been successfully employed to synthesize metal matrix composite powders with Al as the matrix and B4C, Al4Gd and Al4Sm as the reinforcement. The effects of hot rolling on the morphology, mechanical properties as well as the strengthening mechanisms are investigated. Hot rolling results in improving particle distribution and less agglomeration, improving the bonding between particles and matrix and decreasing voids. Thermomechanical processing can increase the density and remove the defects. As increasing rolling deformation to 50%, both YS and UTS of composites are enhanced significantly, showing 25.8 and 27.0% improvement in comparison with composites after sintered, but the elongation changes little. The increase in the yield strength after hot rolling can be attributed to two primary strengthening mechanisms in this work: The coefficient of thermal expansion (CTE) mismatch between B4C, Al4Gd and Al4Sm reinforced particles and Al matrix and the existence of load transfer from Al matrix to the hard reinforced particles.

Effects of Aging Treatment on the Microstructure and Mechanical Properties of a Nanoprecipitates-Strengthened Ferritic Steel

Aging treatment is the primary method to control the strength of nanoprecipitates-strengthened ferritic steels and excellent mechanical properties could be obtained by optimal combination of the size and the density of nanoclusters. In this study, the aging treatments with different time and temperatures are used to control the microstructure, size and density of nanophases. In addition, the distribution of the nanophases and dislocation pattern are observed. It is found that the strength shows an obvious transformation with the aging time and temperatures. However, the microstructures and ductility have not significantly changed with altering aging process. Furthermore, the relationship between the nature of nanophase and mechanical properties is discussed.

Effects of Solid Solution Treatments on the Microstructure and Mechanical Properties of a Nanoscale Precipitate-Strengthened Ferritic Steel

Solid solution treatment (SST) and age hardening are the two main treatments used to produce nanoscale precipitation-strengthened steels. In this work, solution treatment and aging are employed to develop a nanoscale precipitation-strengthened steel displaying high degrees of strength, ductility, and toughness. The effects of SST on the microstructure and mechanical properties of the produced steel are investigated. The results show that the solution temperature strongly influences the matrix microstructure. Partial austenitization between

Effects of Solid Solution Treatment on the Microstructure and Mechanical Properties in the Ultra-High Strength Steel Strengthened by Nanoscale Particles

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Addition of Holmium and Erbium and Hot-Rolling Effects on the Microstructure and Mechanical Properties of Mg–Li Based Alloys

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