Effect of cryogenic treatment on microstructure and mechanical properties of 7A62 Al alloy
The effects of T6 treatment,cryogenic DCT5h-T6 treatment before aging and cryogenic T6-DCT5h treatment after aging on the microstructure and mechanical properties of 7A62 Al alloy were systematically compared by means of XRD,SEM,TEM,hardness test and tensile test.The results show that the precipitated phase size of DCT5h-T6 alloy decreases,while the number density and dislocation density increase after cryogenic treatment,which result in the improvement of strength and elongation of compared with T6 treatment.Compared with the DCT5h-T6 treatment,the cryogenic treatment after aging further promotes the nucleation of the precipitated phase,the numerical density of the precipitated phase increases by 5%,besides,the precipitates have been refined and the distribution is more uniform,so that the T6-DCT5h alloy obtains the higher comprehensive mechanical properties,and its yield strength,tensile strength and elongation reach to 584 MPa,637 MPa and 10.7%,respectively,which are higher than conventional T6 treatment by 28 MPa,10 MPa and 37%,respectively.
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