The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,a...The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,and high-cycle fatigue properties,were studied.The results showed that the LSP induced residual compressive stresses on the surface and near surface of the material.The maximum surface residual compressive stress was−661 MPa,and the compressive-stress-affected depth was greater than 1000μm.The roughness and Vickers micro-hardness increased with the number of shocks,and the maximum hardness-affected depth was about 700μm after three LSP treatments.LSP enhanced the fraction of low-angle grain boundaries,changed the grain preferred orientations,and notably increased the pole density ofαphase on the near surface from 2.41 to 3.46.The surface hardness values of the LSP samples increased with the increase of the number of shocks due to work hardening,while the LSP had a limited effect on the tensile properties.The high-cycle fatigue life of the LSP-treated sample was significantly enhanced by more than 20%compared with that of the untreated sample,which was caused by the suppression of the initiation and propagation of fatigue cracks.展开更多
Semi-solid processing of A380 aluminum alloy was performed by gas induced semi-solid(GISS)process.The effects of argon inert gas flow rate,starting temperature and duration of gas purging as key GISS parameters and al...Semi-solid processing of A380 aluminum alloy was performed by gas induced semi-solid(GISS)process.The effects of argon inert gas flow rate,starting temperature and duration of gas purging as key GISS parameters and also modification with Sr on the structural refinements,hardness and impact strength of GISS alloys were investigated.Microstructural evolution shows that there is an important effect of the pouring temperature and Sr addition on the morphology and size of primaryα(A1)in the alloy to change from coarse dendritic to fine globular structure.The best sample which has fine grains of 51.18μm in average size and a high level of globularity of 0.89 is achieved from a GISS processing of Sr modified alloy in which the gas purging started at 610℃.The impact strength of the GISS optimized samples((4.67±0.18)J/cm^(2))shows an increase of about 40%with respect to the as-cast sample due to the globular structure and fibrous Si morphology.Moreover,the hardness of the optimized GISS sample((89.34±2.85)HB)increases to(93.84±3.14)HB by modification with the Sr and GISS process.The fracture surface of Sr modified alloy is also dominated by complex topography showing typical ductile fracture features.展开更多
基金the National Natural Science Foundation of China(No.52205240).
文摘The effects of laser shock peening(LSP)on the microstructural evolution and mechanical properties of the Ti6242 alloy,including the residual stress,surface roughness,Vickers microhardness,tensile mechanical response,and high-cycle fatigue properties,were studied.The results showed that the LSP induced residual compressive stresses on the surface and near surface of the material.The maximum surface residual compressive stress was−661 MPa,and the compressive-stress-affected depth was greater than 1000μm.The roughness and Vickers micro-hardness increased with the number of shocks,and the maximum hardness-affected depth was about 700μm after three LSP treatments.LSP enhanced the fraction of low-angle grain boundaries,changed the grain preferred orientations,and notably increased the pole density ofαphase on the near surface from 2.41 to 3.46.The surface hardness values of the LSP samples increased with the increase of the number of shocks due to work hardening,while the LSP had a limited effect on the tensile properties.The high-cycle fatigue life of the LSP-treated sample was significantly enhanced by more than 20%compared with that of the untreated sample,which was caused by the suppression of the initiation and propagation of fatigue cracks.
文摘Semi-solid processing of A380 aluminum alloy was performed by gas induced semi-solid(GISS)process.The effects of argon inert gas flow rate,starting temperature and duration of gas purging as key GISS parameters and also modification with Sr on the structural refinements,hardness and impact strength of GISS alloys were investigated.Microstructural evolution shows that there is an important effect of the pouring temperature and Sr addition on the morphology and size of primaryα(A1)in the alloy to change from coarse dendritic to fine globular structure.The best sample which has fine grains of 51.18μm in average size and a high level of globularity of 0.89 is achieved from a GISS processing of Sr modified alloy in which the gas purging started at 610℃.The impact strength of the GISS optimized samples((4.67±0.18)J/cm^(2))shows an increase of about 40%with respect to the as-cast sample due to the globular structure and fibrous Si morphology.Moreover,the hardness of the optimized GISS sample((89.34±2.85)HB)increases to(93.84±3.14)HB by modification with the Sr and GISS process.The fracture surface of Sr modified alloy is also dominated by complex topography showing typical ductile fracture features.
