Effect of post-weld heat treatment on microstructure, hardness and low-temperature impact toughness of electron beam welds of NIFS-HEAT-2 and CEA-J57 heats of V–4Ti–4Cr alloy

Bead-on-plate electron beam welding in high vacuum atmosphere was applied to the plates of NIFS- HEAT-2 and CEA-J57 heats of V–4Ti–4Cr alloy. Effect of post-weld heat treatment (PWHT) in the temper- ature range 673–1273 K on the hardness, impact toughness at 77 K and microstructure of weld metal was investigated. After PWHT at 773 K, hardness of weld metal slightly decreases from 180 HV 100 (as-welded state) to ∼170 HV 100 while absorbed energy increases up to ∼10 J showing ductile fracture mode. PWHT at 973 K results in re-hardening of weld metal up to ∼180 HV 100 caused by re-precipitation of Ti–C,O,N precipitates and corresponding decreasing absorbed energy to ∼2 J with brittle fracture mode. PWHT in- between 1073–1273 K results in gradual recovery of hardness towards values comparable with those of base metal. Impact toughness (77 K) of weld metal after PWHT at 1073K is not recovered nether to the value in as-welded state nor to that one of base metal

Impact properties of electron beam welds of V-4Ti-4Cr alloys NIFS-HEAT-2 and CEA-J57

International audienc

Novel Quaternary TlGaSn2Se6 Single Crystal as Promising Material for Laser Operated Infrared Nonlinear Optical Modulators

The studies of the laser operated third order nonlinear optical features of novel TlGaSn2Se6 crystal were done. The main efforts were devoted to a search of a possibility to apply these crystals as laser operated optoelectronic material. For this reason, the third harmonic generation of the Nd:YAG pulse laser 1064 nm as the fundamental beam with varied energy density of up to 200 J/m2 was studied. As a source of laser operated light, we have used the cw laser (532 nm), exciting the material above the energy gap. Additionally, the influence of middle-energy Ar+ ions on the XPS spectra of the TlInSn2Se6 surface has been explored. We have shown that the main contribution of the Se4p states is manifested in the upper part of the valence band of TlInSn2Se6 We have established that for the TlGaSn2Se6 crystal there exists a possibility of variation of the third harmonic generation efficiency using illumination by external continuous wave laser beam. The discovered effect makes it possible to utilize TlGaSn2Se6 crystal in advanced optoelectronic laser operated devices