1National Engineering Research of Net-Sharp Forming for Metallic Material，South China University of
Technology，Guangzhou 510640，China；2Guangzhou Zoltrix HIP Material Co.，Ltd.，Guangzhou 511458，
China；3Foshan Suizhibo New Materials Technology Co.，Ltd.，Foshan 528247，China
Abstract：In order to improve mechanical properties，the effect of tempered treatment at different holding temperature
ranges from 450 to 700 ℃ on the microstructure and mechanical properties of H13 steel fabricated by selective
laser melting（SLM）were investigated. The microstructural study of the H13 steel by SLM shows both martensite
and austenite phases are existing. With the increasing of tempered temperature，retained austenite and martensite
in the matrix are completely transformed to tempered martensite. The tiny alloy carbide has been gradually
precipitated and grew from matrix. Hardness and tensile tests demonstrate that the hardness and ultimate tensile
strength（UTS）values first increase and then decrease steadily when the holding temperature increases from 450
to 700 ℃. The distinct fracture surface of tensile specimens is changed from tear ridges to dimples. Compared with asbuilt
sample，the microhardness of tempered treatment sample at 550 ℃ is improved from 579.8HV0.5 to 714HV0.5；the
UTS of tempered treatment sample at 600 ℃ reaches 1 958 MPa from 1 479 MPa；the elongation of tempered
treatment sample at 700 ℃ is increased from 4.5% to 11.2%.
2020, Vol. 30 
