The aging-hardening kinetics of powder metallurgy processed 2014Al alloy and its composite have been studied. The existence of n-SiC particulates leads to the increase of peak hardness. Interestingly, the aginghardeni...The aging-hardening kinetics of powder metallurgy processed 2014Al alloy and its composite have been studied. The existence of n-SiC particulates leads to the increase of peak hardness. Interestingly, the aginghardening peak of the composite takes place at earlier time than that of the unreinforced alloy. Transmission electron microscopy（TEM） studies indicated that the major precipitation phases are Al_5Cu_2Mn_3 and θ′（Al_2Cu）. Besides, Ω phase appeared in both specimens at peak hardening condition, which has been rarely observed previously in aluminum metal matrix composites without Ag. Accelerated aging kinetics and increased peak hardness may be attributed to the higher dislocation density resulted from the mismatch of coefficients of thermal expansion between n-SiC and 2014Al matrix. The results are beneficial to fabricating high performance composites for the application in automobile field such as pistons, driveshaft tubes, brake rotors, bicycle frames, railroad brakes.展开更多
In order to improve the mechanical properties of powder metallurgy （P/M） ferrite-pearlite steel, a dual phase （DP） ferrite-martensite steel was produced through intercritical annealing of sintered P/M preforms. Mi...In order to improve the mechanical properties of powder metallurgy （P/M） ferrite-pearlite steel, a dual phase （DP） ferrite-martensite steel was produced through intercritical annealing of sintered P/M preforms. Mi-crostructures of the sintered and DP steels were examined with optical, scanning and transmission electron microscopes. Mechanical properties were evaluated through hardness measurements and compression tests. Microstructural studies revealed that sintered steel contained polygonal ferrite-pearlite while the DP steel contained polygonal, lath and acicular ferrite along with lath-type martensite as microstructural constituents. In DP steels, with increasing mean preform density, the microstructure contained fine and continuous network of martensite colonies with minimum porosity. The work hardening rate vs plastic strain plots （Jaoul-Crussard analysis） of both the steels revealed typical three stage deformation behaviour for low and high mean preform densities. Compression tests revealed that, DP P/M steel displayed higher strength-plasticity combination than the sintered steel.展开更多
基金Financial support by the National Basic Research Program of China(“973”Program,No.2012CB619600)the National Natural Science Foundation of China(No.51474111)+2 种基金the Science and Technology Development Project of Jilin Province(No.20160519002JH)support came from the Fundamental Research Funds for the Central Universities(JCKY-QKJC02)the Chang Bai Mountain Scholars Program(2013014)
文摘The aging-hardening kinetics of powder metallurgy processed 2014Al alloy and its composite have been studied. The existence of n-SiC particulates leads to the increase of peak hardness. Interestingly, the aginghardening peak of the composite takes place at earlier time than that of the unreinforced alloy. Transmission electron microscopy（TEM） studies indicated that the major precipitation phases are Al_5Cu_2Mn_3 and θ′（Al_2Cu）. Besides, Ω phase appeared in both specimens at peak hardening condition, which has been rarely observed previously in aluminum metal matrix composites without Ag. Accelerated aging kinetics and increased peak hardness may be attributed to the higher dislocation density resulted from the mismatch of coefficients of thermal expansion between n-SiC and 2014Al matrix. The results are beneficial to fabricating high performance composites for the application in automobile field such as pistons, driveshaft tubes, brake rotors, bicycle frames, railroad brakes.
文摘In order to improve the mechanical properties of powder metallurgy （P/M） ferrite-pearlite steel, a dual phase （DP） ferrite-martensite steel was produced through intercritical annealing of sintered P/M preforms. Mi-crostructures of the sintered and DP steels were examined with optical, scanning and transmission electron microscopes. Mechanical properties were evaluated through hardness measurements and compression tests. Microstructural studies revealed that sintered steel contained polygonal ferrite-pearlite while the DP steel contained polygonal, lath and acicular ferrite along with lath-type martensite as microstructural constituents. In DP steels, with increasing mean preform density, the microstructure contained fine and continuous network of martensite colonies with minimum porosity. The work hardening rate vs plastic strain plots （Jaoul-Crussard analysis） of both the steels revealed typical three stage deformation behaviour for low and high mean preform densities. Compression tests revealed that, DP P/M steel displayed higher strength-plasticity combination than the sintered steel.
