The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titani...The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titanium matrix composites(TMCs),two-scale network microstructure was constructed including the first-scale network(<150μm)with micro-TiB whisker(TiBw)reinforcement and the second-scale network(<30μm)with nano-Ti5Si3 reinforcement by powder metallurgy and in-situ synthesis.The results showed that the creep rate of the composite was remarkably reduced by an order of magnitude compared with the Ti6Al4V alloy at 550℃,600℃,650℃ under the stresses between 100 MPa and 350 MPa.Moreover,the rupture time of the composite was increased by 20 times,compared with that of the Ti6Al4 Valloy at 550℃/300 MPa.The superior creep resistance could be attributed to the hierarchical microstructure.The micro-TiBw reinforcement in the first-scale network boundary contributed to creep resistance primarily by blocking grain boundary sliding,while the nano-Ti5Si3 particle in the second-scale network boundary mainly by hindering phase boundary sliding.In addition,the nano-Ti5Si3 particle was dissolved,and precipitated with smaller size than the primary Ti5Si3.This phenomenon was attributed to Si element diffusion under high temperature and external stress,which could further continuously enhance the creep resistance.Finally,the creep rate during steady-state stage was significantly decreased,which manifested superior creep resistance of the composite.展开更多
The homogenized Mg-8.2 Gd-3.8 Y-1.0 Zn-0.4 Zr(wt.%)alloy full of plate-shaped long period stacking ordered(LPSO)phases was hot extruded in the atmosphere and cooled by the forced-air,then the effect of forced-air cool...The homogenized Mg-8.2 Gd-3.8 Y-1.0 Zn-0.4 Zr(wt.%)alloy full of plate-shaped long period stacking ordered(LPSO)phases was hot extruded in the atmosphere and cooled by the forced-air,then the effect of forced-air cooling on the microstructure and age-hardening response of the alloy was investigated in this work.The results show that in comparison with the extruded sample cooling in the atmosphere,the forced-air cooling restricts dynamic recrystallization(DRX)and brings about finer dynamic recrystallized(DRXed)grain size,stronger basal texture and higher dislocation density.Furthermore,the forced-air cooling promotes the dynamic precipitation in the DRXed regions and facilitates formation of plate-shaped LPSO phases andγ’phases with smaller interspacing in the unrecrystallized(un DRXed)regions,then slightly restricts the precipitation ofβphases during aging.After peak-ageing treatment,the extruded sample with forced-air cooling shows superior tensile properties with a tensile yield strength of 439 MPa,an ultimate tensile strength of 493 MPa,and elongation to failure of 18.6%.展开更多
The origin of unique parallel alignment of(0001) poles to transverse direction(TD) was investigated using Mg-3Al-0.4Mn(mass%)alloy sheets rolled with different process conditions. When rolling was performed with inter...The origin of unique parallel alignment of(0001) poles to transverse direction(TD) was investigated using Mg-3Al-0.4Mn(mass%)alloy sheets rolled with different process conditions. When rolling was performed with intermediate reheating, the alloy showed a sluggish static recrystallization(SRX) behavior during post-annealing, facilitating the nucleation and growth of statically recrystallized grains from extension twins. This resulted in the apparent texture component with the parallel alignment of the(0001) poles to the TD, and the sheet exhibited good ductility for both the rolling direction(RD) and TD. In contrast, continuous rolling without intermediate reheating led to the formation of severely deformed regions near double twins. SRX was promoted at such regions, forming a typical basal textural feature with weak RD-split of the(0001) poles. Although extension twins were formed after the continuous rolling, SRX was facilitated at the severely deformed regions with double twins, and the formation of the unique alignment of the(0001) poles to the TD was suppressed. The RD-split texture led to the large elongation to failure along the RD, while it along the TD decreased owing to the narrow distribution of the(0001)poles toward the TD, resulting in the in-plane anisotropy in ductility.展开更多
基金financially supported by the National Key R&D Program of China (No. 2017YFB0703100)the National Natural Science Foundation of China (NSFC) under Grant Nos. 51822103, 51671068 and 51731009the Fundamental Research Funds for the Central Universities (No. HIT.BRETIV.201902)
文摘The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titanium matrix composites(TMCs),two-scale network microstructure was constructed including the first-scale network(<150μm)with micro-TiB whisker(TiBw)reinforcement and the second-scale network(<30μm)with nano-Ti5Si3 reinforcement by powder metallurgy and in-situ synthesis.The results showed that the creep rate of the composite was remarkably reduced by an order of magnitude compared with the Ti6Al4V alloy at 550℃,600℃,650℃ under the stresses between 100 MPa and 350 MPa.Moreover,the rupture time of the composite was increased by 20 times,compared with that of the Ti6Al4 Valloy at 550℃/300 MPa.The superior creep resistance could be attributed to the hierarchical microstructure.The micro-TiBw reinforcement in the first-scale network boundary contributed to creep resistance primarily by blocking grain boundary sliding,while the nano-Ti5Si3 particle in the second-scale network boundary mainly by hindering phase boundary sliding.In addition,the nano-Ti5Si3 particle was dissolved,and precipitated with smaller size than the primary Ti5Si3.This phenomenon was attributed to Si element diffusion under high temperature and external stress,which could further continuously enhance the creep resistance.Finally,the creep rate during steady-state stage was significantly decreased,which manifested superior creep resistance of the composite.
基金financially supported by the National Natural Science Foundation for Young Scientists of China(Nos.51801042 and 51704088)the National Natural Science Foundation(Nos.51971075 and 51775150)+2 种基金the Fundamental Research Funds for the Central Universitiesthe JST Advanced Low Carbon Technology Researchthe Development Program(ALCA)(No.12102886)。
文摘The homogenized Mg-8.2 Gd-3.8 Y-1.0 Zn-0.4 Zr(wt.%)alloy full of plate-shaped long period stacking ordered(LPSO)phases was hot extruded in the atmosphere and cooled by the forced-air,then the effect of forced-air cooling on the microstructure and age-hardening response of the alloy was investigated in this work.The results show that in comparison with the extruded sample cooling in the atmosphere,the forced-air cooling restricts dynamic recrystallization(DRX)and brings about finer dynamic recrystallized(DRXed)grain size,stronger basal texture and higher dislocation density.Furthermore,the forced-air cooling promotes the dynamic precipitation in the DRXed regions and facilitates formation of plate-shaped LPSO phases andγ’phases with smaller interspacing in the unrecrystallized(un DRXed)regions,then slightly restricts the precipitation ofβphases during aging.After peak-ageing treatment,the extruded sample with forced-air cooling shows superior tensile properties with a tensile yield strength of 439 MPa,an ultimate tensile strength of 493 MPa,and elongation to failure of 18.6%.
基金supported by JSPS KAKENHI Grant Numbers JP22H00259,JP22K18900,JP21H01669The Light Metal Educational Foundation,Inc.,Japan+1 种基金National Natural Science Foundation of China (51971075,52220105003)National Key Research & Development Program of China (2021YFB3703300,2022YFE0110600)。
文摘The origin of unique parallel alignment of(0001) poles to transverse direction(TD) was investigated using Mg-3Al-0.4Mn(mass%)alloy sheets rolled with different process conditions. When rolling was performed with intermediate reheating, the alloy showed a sluggish static recrystallization(SRX) behavior during post-annealing, facilitating the nucleation and growth of statically recrystallized grains from extension twins. This resulted in the apparent texture component with the parallel alignment of the(0001) poles to the TD, and the sheet exhibited good ductility for both the rolling direction(RD) and TD. In contrast, continuous rolling without intermediate reheating led to the formation of severely deformed regions near double twins. SRX was promoted at such regions, forming a typical basal textural feature with weak RD-split of the(0001) poles. Although extension twins were formed after the continuous rolling, SRX was facilitated at the severely deformed regions with double twins, and the formation of the unique alignment of the(0001) poles to the TD was suppressed. The RD-split texture led to the large elongation to failure along the RD, while it along the TD decreased owing to the narrow distribution of the(0001)poles toward the TD, resulting in the in-plane anisotropy in ductility.
