The β-Si3N4 whiskers (β-Si3N4w) reinforced A1 matrix com posites were first fabricated by hot pressing, then treated through hot extrusion. The microstructure characterization dem onstrated the preferred orientation...The β-Si3N4 whiskers (β-Si3N4w) reinforced A1 matrix com posites were first fabricated by hot pressing, then treated through hot extrusion. The microstructure characterization dem onstrated the preferred orientations of both β-Si3N4w and A1 grains in the as-extruded composites. It indicated th at β-Si3N4w were aligned along the extrusion direction and A1 grains exhibited a distinct <111>ai texture. The interface betw een β-Si3N4w and A1 was in a good bonding status without voids and reaction products. Effects of extrusion process on the mechanical properties of com posites were also investigated. The results indicated the extrusion process had a prom inent strengthening effect on the mechanical properties of composites. The maxim umyield strength and ultim ate tensile strength of com posites reached up to 170 and 289 MPa, respectively, accompanied by a 12.3% elongation at fracture w hen the w hisker fraction was 15 vol.%. This im provem ent was collectively attributed to the densification of composites, the strong interface, and the preferred orientation inside composites. The yield strength of the composites reinforced with 5 vol.%β-Si3N4w corresponded well w ith the theoretical value from different strengthening mechanisms.展开更多
Cu matrix composites reinforced by TiB_(2)/TiN ceramic reinforcements(Cu/TBN composites)were prepared by hot pressing method.Prior to the hot pressing,Cu/TiB_(2)/TiN composite powders(CTBN powders),which were used as ...Cu matrix composites reinforced by TiB_(2)/TiN ceramic reinforcements(Cu/TBN composites)were prepared by hot pressing method.Prior to the hot pressing,Cu/TiB_(2)/TiN composite powders(CTBN powders),which were used as the starting materials of Cu/TBN composites,were fabricated by self-propagating high-temperature synthesis method.The CTBN particles were found to be in a special core–shell structure with a Cu–Ti alloy core and a TiB_(2)/TiN ceramic shell.The test results presented obvious improvements in mechanical properties.The highest ultimate tensile strength reached up to 297 MPa,77 MPa higher than that of Cu.And the highest hardness reached up to 70.7 HRF,15.7 HRF higher than that of Cu.A comparative study indicated that the core–shell structured particles could bring about more obvious strengthening eff ect than the traditional irregularly shaped particles,which was due to the improved Cu/ceramics interfacial bonding,the linkage strengthening effect of both TiB_(2) and TiN,and higher load bearing ability of the core–shell structured reinforcements.展开更多
基金supported by National Key R&D Program of China (Nos. 2017YFB0406200, 2017YFB0703200, and 2017YFB0310400)the National Natural Science Foundation of China (No. 51501215), Shanghai Sailing Program (No. 16YF1412900)+1 种基金Science Foundation for Youth Scholar of State Key Laboratory of High Performance Ceramics and Superfine Microstructures (No. SKL201701)State Key Laboratory of New Ceramic and Fine Processing Tsinghua University (No. KF201806)
文摘The β-Si3N4 whiskers (β-Si3N4w) reinforced A1 matrix com posites were first fabricated by hot pressing, then treated through hot extrusion. The microstructure characterization dem onstrated the preferred orientations of both β-Si3N4w and A1 grains in the as-extruded composites. It indicated th at β-Si3N4w were aligned along the extrusion direction and A1 grains exhibited a distinct <111>ai texture. The interface betw een β-Si3N4w and A1 was in a good bonding status without voids and reaction products. Effects of extrusion process on the mechanical properties of com posites were also investigated. The results indicated the extrusion process had a prom inent strengthening effect on the mechanical properties of composites. The maxim umyield strength and ultim ate tensile strength of com posites reached up to 170 and 289 MPa, respectively, accompanied by a 12.3% elongation at fracture w hen the w hisker fraction was 15 vol.%. This im provem ent was collectively attributed to the densification of composites, the strong interface, and the preferred orientation inside composites. The yield strength of the composites reinforced with 5 vol.%β-Si3N4w corresponded well w ith the theoretical value from different strengthening mechanisms.
基金financially supported by the National Key R&D Program of China(No.2018YFF01013605)the National Natural Science Foundation of China(No.51501215)+2 种基金the Youth Innovation Promotion Association CAS(No.2019254)the Science Foundation for Youth Scholar of State Key Laboratory of High Performance Ceramics and Superfine Microstructures(No.SKL201701)the State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KF201806)。
文摘Cu matrix composites reinforced by TiB_(2)/TiN ceramic reinforcements(Cu/TBN composites)were prepared by hot pressing method.Prior to the hot pressing,Cu/TiB_(2)/TiN composite powders(CTBN powders),which were used as the starting materials of Cu/TBN composites,were fabricated by self-propagating high-temperature synthesis method.The CTBN particles were found to be in a special core–shell structure with a Cu–Ti alloy core and a TiB_(2)/TiN ceramic shell.The test results presented obvious improvements in mechanical properties.The highest ultimate tensile strength reached up to 297 MPa,77 MPa higher than that of Cu.And the highest hardness reached up to 70.7 HRF,15.7 HRF higher than that of Cu.A comparative study indicated that the core–shell structured particles could bring about more obvious strengthening eff ect than the traditional irregularly shaped particles,which was due to the improved Cu/ceramics interfacial bonding,the linkage strengthening effect of both TiB_(2) and TiN,and higher load bearing ability of the core–shell structured reinforcements.
