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The hydrogen-induced stress corrosion cracking (HISCC) behavior of SUS301L-MT stainless steel laser-arc hybrid welding (LAHW) joints was investigated using slow strain rate tensile (SSRT) method in 3.5 wt.% NaCl solution under different cathodic potentials. With the negative shift of applied potentials from open circle potential (OCP) to −1400 mV SCE , the HISCC susceptibility index ( I SSRT ) decreased from 0.15 (OCP) to 0.06 (−400 mV SCE ), then increased to 0.28 (−1400 mV SCE ). The specimens tested in air and under OCP to −800 mV ruptured in weld metal zone with ductile features of dimples. While with the potential turned more negative, the specimens ruptured in base metal zone with brittle features of transgranular cleave in martensite, intergranular failure and secondary cracks [Chen et al., Int. J. Adv. Manuf. Technol.73, 1695 (2014)]. [ABSTRACT FROM AUTHOR]

The stress corrosion cracking (SCC) behaviors at slow strain rate tensile (SSRT) test of AISI301L stainless steel laser-MIG welded joints in 3.5 wt.% NaCl solution at 20C, 40C and 60C were investigated. The results showed that the weld metal composed of as-cast with -Fe and austenite. The base metal (BM) and heat affected zone (HAZ) contained strain-induced M phase. The stress and strain decreased with the increasing temperature. The SCC cracks are initiated by anodic dissolution at 20C. Besides the anodic dissolution mechanism, hydrogen-induced SCC mechanism had appeared in 3.5 wt.% NaCl solution at 40C and 60C. [ABSTRACT FROM AUTHOR]

The Al-Zn-Mg aluminum alloy A7N01S-T5 used in high speed trains was designed by orthogonal method. The effect of elemental composition on the tensile properties and fracture toughness has been investigated. The alloys with different compositions were tested by tensile and three point bending tests: the range analysis results showed that the compositions of Zn and Mg were the main factors that affect the strength and plasticity of the alloys. The tensile testing results showed that the #1 alloy Al-4.34Zn-1.43 Mg-0.27Mn-0.13Cr-0.12Zr-0.07Ti had the best combination of tensile strength, yield strength and elongation, which were 415 MPa, 378 MPa and 13.5%, respectively. Furthermore, this alloy showed the excellent ability to hinder the crack propagation with a value of J0.2BL(12) = 23.37 kJ·m-2. The microstructure, grain size, compositions and fracture characteristics of the alloy were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), backscattered electron diffraction (EBSD) and transmission electron microscopy (TEM). The results indicated that the strength is mainly determined by the volume fraction, size and distribution of precipitated n(MgZn2) phase. The discontinuous distribution of n(MgZn2) phase, narrow precipitated-free zones (PFZs) and fine grain size played important roles to obtain high fracture toughness. [ABSTRACT FROM AUTHOR]

Nanostructured and ultrafine WC–17Co coatings have been prepared by means of the high velocity oxyfuel (HVOF) technique. The structures of the two feedstock powders were analysed. The wear resistances at the elevated temperature (600°C) of the two coatings were compared using GCr15 steel as a counterpart in sliding wear tests. The results show that the WC particles are of nanosize, ranging from 50 to 500 nm. Finer subparticles of 2–5 nm are also found, composed of the nanosized WC particles. These subparticles can act as crystallising nuclei and make the grains much finer during the HVOF spraying process, which is beneficial to the formation of nanostructure in the coating. The wear resistance and fracture toughness of the nanostructured coatings at elevated temperatures are better than that of ultrafine coatings. [ABSTRACT FROM AUTHOR]