Heat-affected zone

About: Heat-affected zone is a research topic. Over the lifetime, 18787 publications have been published within this topic receiving 231744 citations.

Role of evolving microstructure on the mechanical properties of electron beam welded ferritic-martensitic steel in the as-welded and post weld heat-treated states

Abstract: The microstructure and mechanical properties of electron beam welded joints of reduced activation ferritic-martensitic steel in the as-welded and post-weld heat treatment (PWHT) states have been explored. The as-received base metal (BM) was in normalised and tempered condition. The PWHTs employed include post-weld direct tempering (PWDT) at 760 °C/90 min/air cooling and (ii) re-austenitizing at 980 °C/30 min/air cooling+ tempering at 760 °C/90 min/air cooling (PWNT). The BM microstructure was composed of fully tempered lath martensite with prior austenite grain and martensite lath boundaries decorated with M 23 C 6 type carbides whereas intra-lath regions majorly displayed MX type carbides. In the as-welded state, the fusion zone (FZ) contained martensite in coarse grains and small amount of δ-ferrite with no evidence for precipitation of M 23 C 6 and MX either in intra- or inter-granular regions. The heat affected zone (HAZ) was made up of martensite in fine grains without any δ-ferrite and with subtle variations in microstructure across the HAZ. The as-welded joints exhibited high hardness in the FZ and HAZ due to the occurrence of martensite during the weld thermal cycle. The impact toughness of the as-welded joint was inferior compared to that of the BM due to the combined influence of the martensite, coarse grains and presence of δ-ferrite in the weld zone. Tensile strength of as-welded joint was higher than that of BM. PWHTs were beneficial in decreasing the hardness in the FZ and HAZ. PWDT could not fully eliminate the pronounced variation of hardness observed in the transverse section of welded joint. Though the impact toughness of the weld joint was improved marginally compared to as-welded state after PWDT, it was much lower than that recorded in the case of BM. PWNT treatment minimised the variation in hardness across the transverse section of weld joint and the impact toughness surpassed than that achieved in BM. The tensile properties of BM, welded joints in as-welded and in PWHT conditions were determined at room temperature and correlated with the prevailing microstructures.

Effect of heat treatment on tensile properties of friction stir welded joints of 2219-T6 aluminium alloy

Abstract: The effect of post-weld heat treatment (PWHT) on the tensile properties of friction stir welded (FSW) joints of 2219-T6 aluminium alloy was investigated. The PWHT was carried out at aging temperature of 165uC for 18 h. The mechanical properties of the joints were evaluated using tensile tests. The experimental results indicate that the PWHT significantly influences the tensile properties of the FSW joints. After the heat treatment, the tensile strength of the joints increases and the elongation at fracture of the joints decreases. The maximum tensile strength of the joints is equivalent to 89% of that of the base material. The fracture location characteristics of the heat treated joints are similar to those of the as welded joints. The defect free joints fracture in the heat affected zone on the retreating side and the joints with a void defect fracture in the weld zone on the advancing side. All of the experimental results can be explained by the hardness profiles and welding defects in the joints.

Characterization of the multi-pass weld metal and the impact of retained austenite obtained through intercritical heat treatment on low temperature toughness

Abstract: In this study, we explore the relationship between the microstructure and low temperature toughness of weld metal obtained from a real multi-pass weld joint (up to 55 mm) by submerged arc welding, which was developed for high strength (yield strength over 550 MPa) and heavy wall pipe fitting applications with composition of 0.1 wt% C, 2.0 wt% Mn and other micro-alloys. The study indicated that the necklace-type coarse martensite–austenite (M–A) constituent formed in the interlayer heat affected zone (IHAZ) of weld metal was responsible for low impact energy of 39 J at −40 °C. To enhance the toughness, conventional tempering and new intercritical heat treatment were designed. The results suggested that there was insignificant effect on toughness through conventional tempering, but obvious improvement through combination of quenching plus intercritical annealing and tempering. The impact energy was increased to ~98 J. The microstructure that benefit toughness primarily comprised of intercritical lath-like ferrite or acicular-type ferrite, bainite/martensite, and fine acicular retained austenite, with average size of ~0.3 μm. Retained austenite with volume fraction of ~6% was formed by the enrichment of Mn and Ni in reversed austenite during intercritical tempering process.