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Effect of Heat Treatment on Microstructure and Impact Toughness of Ti-6Al-4V Manufactured by Selective Laser Melting Process

Lee K.-A., Kim Y.-K., Yu J.-H., Park S.-H., Kim M.-C.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 2B

1341--1346

This study manufactured Ti-6Al-4V alloy using one of the powder bed fusion 3D-printing processes, selective laser melting, and investigated the effect of heat treatment (650°C/3hrs) on microstructure and impact toughness of the material. Initial microstructural observation identified prior-β grain along the building direction before and after heat treatment. In addition, the material formed a fully martensite structure before heat treatment, and after heat treatment, α and β phase were formed simultaneously. Charpy impact tests were conducted. The average impact energy measured as 6.0 J before heat treatment, and after heat treatment, the average impact energy increased by approximately 20% to 7.3 J. Fracture surface observation after the impact test showed that both alloys had brittle characteristics on macro levels, but showed ductile fracture characteristics and dimples at micro levels.

Effect Of The Desorption-Recombination Temperature On The Microstructure And Magnetic Properties Of HDDR Processed Nd-Fe-B Powders

Lee J.-G., Cha H.-R., Liu S., Yu J.-H., Baek Y.-K., Kwon H.-W.

Archives of Metallurgy and Materials

2015

Vol. 60, iss. 2B

1499--1501

The effect of the desorption-recombination temperature on the microstructure and magnetic properties of hydrogenation-disproportionation-desorption-recombination (HDDR) processed Nd-Fe-B powders was studied. The NdxB6.4Ga0.3Nb20.2Febal (x=12.5-13.5, at.%) casting alloys were pulverized after homogenizing annealing, and then subjected to HDDR treatment. During the HDDR process, desorption-recombination (DR) reaction was induced at two different temperature, 810°C and 820°C. The higher Nd content resulted in enhanced coercivity of the HDDR powder, and which was attributed to the thicker and more uniform Nd-rich phase along grain boundaries. But this uniform Nd-rich phase induced faster grain growth. The remanence of the powder DR-treated at 820°C is higher than that DR-treated at 810°C. In addition, it was also confirmed that higher DR temperature is much more effective to improve squareness.