Investigation on the microstructure and mechanical behaviour of post-weld heat treated AA6351 aluminium weldments

The present study focuses on the metallurgical and corrosion characterization of post weld heat treated duplex stainless steel joints. After friction welding, it was confirmed that there is an increase in ferrite content at weld interface due to dynamic recrystallization. This caused the weldments prone to pitting corrosion attack. Hence the post weld heat treatments were performed at three temperatures 1080[Formula: see text]C, 1150[Formula: see text]C and 1200[Formula: see text]C with 15[Formula: see text]min of aging time. This was followed by water and oil quenching. The volume fraction of ferrite to austenite ratio was balanced and highest pit nucleation resistance were achieved after PWHT at 1080[Formula: see text]C followed by water quench and at 1150[Formula: see text]C followed by oil quench. This had happened exactly at parameter set containing heating pressure (HP):40 heating time (HT):4 upsetting pressure (UP):80 upsetting time (UP):2 (experiment no. 5). Dual phase presence and absence of precipitates were conformed through TEM which follow Kurdjumov–Sachs relationship. PREN of ferrite was decreasing with increase in temperature and that of austenite increased. The equilibrium temperature for water quenching was around 1100[Formula: see text]C and that for oil quenching was around 1140[Formula: see text]C. The pit depths were found to be in the range of 100[Formula: see text]nm and width of 1.5–2[Formula: see text][Formula: see text]m.

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Structure–property relationships of PCGTA welds of Inconel X750 in as-welded and post-weld heat treated conditions—A comparative study

Journal of Manufacturing Processes ◽

10.1016/j.jmapro.2015.10.003 ◽

2015 ◽

Vol 20 ◽

pp. 1-14 ◽

Cited By ~ 10

Author(s):

K. Devendranath Ramkumar ◽

S. Rahul Krishnan ◽

R. Ramanand ◽

S. Logesh ◽

Tushar Satyandas ◽

...

Keyword(s):

Comparative Study ◽

Structure Property ◽

Structure Property Relationships ◽

Heat Treated ◽

Inconel X750 ◽

Weld Heat

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An investigation on microstructure and mechanical properties of post-weld heat-treated friction stir welds in aluminum alloy 2024-W

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406212452479 ◽

2012 ◽

Vol 227 (4) ◽

pp. 649-662 ◽

Cited By ~ 3

Author(s):

Hakan Aydın ◽

Ali Bayram ◽

İsmail Durgun

Keyword(s):

Room Temperature ◽

Welded Joint ◽

Solution Treatment ◽

Heat Treatments ◽

Maximum Hardness ◽

Friction Stir ◽

Base Materials ◽

Heat Treated ◽

Aluminum Alloy 2024 ◽

Weld Heat

The present work describes the results obtained from microstructural and mechanical evaluation of post-weld heat treated friction stir welds of 2024 aluminum alloys in the W temper state. Post-weld heat treatments have been carried out at 510 °C for 2.5 h followed by ageing at room temperature for 6 months, at 100 °C and 190 °C for 10 h, and by cooling in static air (O-temper). The solution treatment caused abnormal coarsening of the grains in the stir zone, which resulted in a drop in microhardness. The strength of the as-welded joint was significantly incrased by post weld heat treatments. The maximum hardness and strength values were obtained in T6 (190 °C, 10 h) treated joint. However, the T6 (190 °C, 10 h) treated joint had the lowest ductility. On the other hand, the tensile properties of the post-weld heat treated joints were far lower than those of the unwelded base materials in the same temper states. In addition, the post-weld heat treatments did not significantly change the fracture locations of the friction stir welds.

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Analysis of Strain Hardening Behaviour of Cast Aluminium Alloy 354 Subjected to Artificial Ageing at Various Temperatures

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.856.231 ◽

2013 ◽

Vol 856 ◽

pp. 231-235 ◽

Cited By ~ 1

Author(s):

Aditya Eswar ◽

Arnav Gupta ◽

G. Dinesh Babu ◽

M. Nageswara Rao

Keyword(s):

Heat Treatment ◽

Aluminium Alloy ◽

Strain Hardening ◽

Automotive Industry ◽

Mechanical Behaviour ◽

Artificial Ageing ◽

Cast Aluminium ◽

Heat Treated ◽

Lower Strain ◽

Wide Scale

Automotive industry makes wide scale use of cast aluminium alloy 354 in the production of crucial components, such as compressor wheels for turbochargers. The compressor wheels undergo T61 heat treatment, involving artificial ageing at 188°C. This study focuses on the possible improvement of the mechanical behaviour of the components by subjecting them to modified heat treatments involving usage of lower artificial ageing temperatures (160, 171 and 177°C). A comparative analysis of tensile properties and strain hardening behaviour has been carried out with different artificial ageing temperatures. Results showed that the heat treatment routinely employed by the industry (aged at 188°C) leads to overageing, thereby resulting in relatively inferior mechanical properties and lower strain hardening rates as compared to the samples heat treated at lower artificial ageing temperatures. It is concluded that lowering of the artificial ageing temperature can lead to a superior state of components with respect to mechanical behaviour.

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Effect of post-weld heat treatment on thermal diffusivity in UNS S32304 duplex stainless steel welds

Archives of Materials Science and Engineering ◽

10.5604/01.3001.0010.8039 ◽

2017 ◽

Vol 2 (88) ◽

pp. 49-58

Author(s):

E.G. Betini ◽

C.S. Mucsi ◽

T.S. Luz ◽

M.T.D. Orlando ◽

M-N. Avettand-Fènoël ◽

...

Keyword(s):

Heat Treatment ◽

Stainless Steel ◽

Thermal Diffusivity ◽

Duplex Stainless Steel ◽

Welding Process ◽

Austenite Phase ◽

Shielding Gas ◽

Heat Treated ◽

Steel Welds ◽

Weld Heat

Purpose: The thermal diffusivity variation of UNS S32304 duplex stainless steel welds was studied after pulsed GTA welding autogenous process without filler addition. This property was measured in the transverse section of thin plates after welding process and post-heat treated at 750°C for 8 h followed by air-cooling. Design/methodology/approach: The present work reports measurements of thermal diffusivity using the laser-flash method. The thermal cycles of welding were acquired during welding by means of k-type thermocouples in regions near the weld joint. The used shielding gas was pure argon and 98% argon plus 2% of nitrogen. The temperature profiles were obtained using a digital data acquisition system. Findings: It was found an increase of thermal diffusivity after welding process and a decrease of these values after the heat treatment regarding the solidified weld pool zone, irrespective of the welding protection atmosphere. The microstructure was characterized and an increase of austenite phase in the solidified and heat-affected zones was observed for post-weld heat-treated samples. Research limitations/implications: It suggests more investigation and new measurements about the influence of the shielding gas variation on thermal diffusivity in the heat-affected zone. Practical implications: The nuclear industry, especially, requests alloys with high thermal stability in pipes for power generation systems and safe transportation equipment’s for radioactive material. Thus, the duplex stainless steel grades have improved this stability over standard grades and potentially increase the upper service temperature reliability of the equipment. Originality/value: After heat treatment, the welded plate with 98%Ar plus 2%N2 as shielding gas presented a thermal diffusivity closer to the as received sample. By means of 2%-nitrogen addition in shielding gas during GTAW welding of duplex stainless steel may facilitate austenite phase reformation, and then promotes stability on the thermal diffusivity of duplex stainless steels alloys.

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