The effect of stress-relief annealing at different stages of thermal fatigue tests on crack growth was investigated using a self-built thermal cycle setup.The results showed that annealing could limit crack expansion ...The effect of stress-relief annealing at different stages of thermal fatigue tests on crack growth was investigated using a self-built thermal cycle setup.The results showed that annealing could limit crack expansion effectively.It reduced dislocation density and released the accumulation of residual stress.In addition,the strain accumulation in carbides was reduced by this process.It was also found that double annealing was even more effective at inhibiting crack expansion compared to single stress-relief annealing.After 1000 cycles,the maximum crack length was reduced by 31.1%and 45.2%for the samples after using the optimal single and double annealing processes,respectively.For single stress-relief annealing,earlier annealing provides more benefit in delaying crack expansion.However,effective double stress-relief annealing requires a suitable time interval between the annealing steps.Besides,after 800 cycles,surface hardness decreased significantly accompanied by an increase in the size and number of carbides,and cracks expanded predominantly along grain boundaries.展开更多
为探究低温解除后苜蓿光合作用恢复过程中的限制位点,以‘新牧4号’和‘甘农5号’2个品种紫花苜蓿为材料,测定其低温胁迫及恢复过程中苜蓿叶片光合活性的变化。结果表明,低温胁迫下2个苜蓿品种叶片叶绿素含量、净光合速率以及光系统Ⅱ(p...为探究低温解除后苜蓿光合作用恢复过程中的限制位点,以‘新牧4号’和‘甘农5号’2个品种紫花苜蓿为材料,测定其低温胁迫及恢复过程中苜蓿叶片光合活性的变化。结果表明,低温胁迫下2个苜蓿品种叶片叶绿素含量、净光合速率以及光系统Ⅱ(photosystemⅡ,PSⅡ)活性显著下降,非光化学淬灭系数(nonphotochemical quenching factor,NPQ)显著上升,但对光系统Ⅰ(photosystemⅠ,PSⅠ)的活性无显著影响;其中,‘甘农5号’叶绿素对低温更敏感,含量下降较多。室温恢复72 h后,2个品种苜蓿叶片PSⅡ的活性及净光合速率都有上升但均未恢复至处理前水平;NPQ缓慢下降至处理前水平,‘甘农5号’NPQ较‘新牧4号’更高,表明在恢复过程中仍有过剩光能需通过NPQ消耗。苜蓿叶片的电子传递链在低温下受抑制显著,恢复72 h后PSⅡ受体侧活性基本恢复至处理前,而PSⅡ供体侧活性显著下降。2个品种苜蓿单位反应中心捕获的用于电子传递的能量(energy captured by unit reaction center for electron transfer,ETO/RC)和单位反应中心捕获的用于还原QA的能量(energy captured by the unit reaction center for reducing QA,TRO/RC)在低温处理72 h后显著下降,解除低温后恢复至处理前水平,且2个品种无显著差异;2个苜蓿品种单位反应中心耗散掉的能量(energy dissipated by the unit reaction center,DIO/RC)未恢复至处理前水平,且‘甘农5号’在恢复72 h后DIO/RC显著升高。综上,低温胁迫显著伤害紫花苜蓿叶片光合机构,降低了光合速率,光合速率未恢复到处理前与PSⅡ的活性显著相关,限制光合作用恢复的位点在其供体侧,非光化学淬灭是恢复24 h过剩光能的主要分配途径。展开更多
基金Acknowledgments The program was supported by the National Natural Science Foundation of China （51427804） and the Open Found of State Key Laboratory of Deep Coal Mining ＆ Environment Protection.
基金supported by the Key Research and Development Program of Guangdong Province,China(Grant No.2020B010184002).
文摘The effect of stress-relief annealing at different stages of thermal fatigue tests on crack growth was investigated using a self-built thermal cycle setup.The results showed that annealing could limit crack expansion effectively.It reduced dislocation density and released the accumulation of residual stress.In addition,the strain accumulation in carbides was reduced by this process.It was also found that double annealing was even more effective at inhibiting crack expansion compared to single stress-relief annealing.After 1000 cycles,the maximum crack length was reduced by 31.1%and 45.2%for the samples after using the optimal single and double annealing processes,respectively.For single stress-relief annealing,earlier annealing provides more benefit in delaying crack expansion.However,effective double stress-relief annealing requires a suitable time interval between the annealing steps.Besides,after 800 cycles,surface hardness decreased significantly accompanied by an increase in the size and number of carbides,and cracks expanded predominantly along grain boundaries.
文摘为探究低温解除后苜蓿光合作用恢复过程中的限制位点,以‘新牧4号’和‘甘农5号’2个品种紫花苜蓿为材料,测定其低温胁迫及恢复过程中苜蓿叶片光合活性的变化。结果表明,低温胁迫下2个苜蓿品种叶片叶绿素含量、净光合速率以及光系统Ⅱ(photosystemⅡ,PSⅡ)活性显著下降,非光化学淬灭系数(nonphotochemical quenching factor,NPQ)显著上升,但对光系统Ⅰ(photosystemⅠ,PSⅠ)的活性无显著影响;其中,‘甘农5号’叶绿素对低温更敏感,含量下降较多。室温恢复72 h后,2个品种苜蓿叶片PSⅡ的活性及净光合速率都有上升但均未恢复至处理前水平;NPQ缓慢下降至处理前水平,‘甘农5号’NPQ较‘新牧4号’更高,表明在恢复过程中仍有过剩光能需通过NPQ消耗。苜蓿叶片的电子传递链在低温下受抑制显著,恢复72 h后PSⅡ受体侧活性基本恢复至处理前,而PSⅡ供体侧活性显著下降。2个品种苜蓿单位反应中心捕获的用于电子传递的能量(energy captured by unit reaction center for electron transfer,ETO/RC)和单位反应中心捕获的用于还原QA的能量(energy captured by the unit reaction center for reducing QA,TRO/RC)在低温处理72 h后显著下降,解除低温后恢复至处理前水平,且2个品种无显著差异;2个苜蓿品种单位反应中心耗散掉的能量(energy dissipated by the unit reaction center,DIO/RC)未恢复至处理前水平,且‘甘农5号’在恢复72 h后DIO/RC显著升高。综上,低温胁迫显著伤害紫花苜蓿叶片光合机构,降低了光合速率,光合速率未恢复到处理前与PSⅡ的活性显著相关,限制光合作用恢复的位点在其供体侧,非光化学淬灭是恢复24 h过剩光能的主要分配途径。
