Solidification rate in laser welding and its influence on AA 2024 weld quality

2005 ◽  
Author(s):  
Bin Hu ◽  
Ian M. Richardson
Keyword(s):  
Laser Welding ◽  
Solidification Rate ◽  
Weld Quality ◽  
Aa 2024

scholarly journals Development of laser welding of high strength aluminium alloy 2024-T4 with controlled thermal cycle

2020 ◽  
Vol 326 ◽  
pp. 08005
Author(s):  
Mete Demirorer ◽  
Wojciech Suder ◽  
Supriyo Ganguly ◽  
Simon Hogg ◽  
Hassam Naeem
Keyword(s):  
Laser Beam ◽  
Laser Welding ◽  
Heat Input ◽  
Thermal Cycle ◽  
Laser Beam Welding ◽  
Base Material ◽  
High Strength ◽  
Cooling Rates ◽  
Aa 2024 ◽  
Welding Processes

An innovative process design, to avoid thermal degradation during autogenous fusion welding of high strength AA 2024-T4 alloy, based on laser beam welding, is being developed. A series of instrumented laser welds in 2 mm thick AA 2024-T4 alloys were made with different processing conditions resulting in different thermal profiles and cooling rates. The welds were examined under SEM, TEM and LOM, and subjected to micro-hardness examination. This allowed us to understand the influence of cooling rate, peak temperature, and thermal cycle on the growth of precipitates, and related degradation in the weld and heat affected area, evident as softening. Although laser beam welding allows significant reduction of heat input, and higher cooling rates, as compared to other high heat input welding processes, this was found insufficient to completely supress coarsening of precipitate in HAZ. To understand the required range of thermal cycles, additional dilatometry tests were carried out using the same base material to understand the time-temperature relationship of precipitate formation. The results were used to design a novel laser welding process with enhanced cooling, such as with copper backing bar and cryogenic cooling.

Visual Evaluation of Cast Dental Alloys Welds Discontinuities in the Field of Fixed Prosthodontics

2011 ◽  
Vol 383-390 ◽  
pp. 4058-4064
Author(s):  
Sorin Porojan ◽  
Liliana Sandu ◽  
Florin Topală
Keyword(s):  
Laser Welding ◽  
Base Metal ◽  
Visual Inspection ◽  
Incomplete Fusion ◽  
Weld Quality ◽  
Dental Alloys ◽  
Visual Evaluation ◽  
Fixed Prosthodontics ◽  
Microplasma Welding

It is essential for a weld to satisfy the requirements of certain standards in the field where it is applied. The aim of the study was to highlight the discontinuities which can appear in the joints achieved by laser and microplasma welding of base metal dental alloys used in fixed prosthodontics. All types of discontinuities which are visible from visual inspection were searched: inclusions, inadequate joint penetration, incomplete fusion, undercuts, overlaps, underfills. Recognizing the defects and discontinuities and their delimitation was essential in determining the weld quality. The obtained results were satisfactory for the purpose both for microplasma and laser welding. Using these methods, welds without defects, which meet minimum acceptable standards for each case, could be obtained.

Laser welding of the AA 2024-T3 aluminum alloy by using two different laser sources (Nd:YAG or CO 2 )

2005 ◽  
Author(s):  
Antonio D. Ludovico ◽  
Giuseppe Daurelio ◽  
L. A. C. De Filippis ◽  
A. Scialpi ◽  
F. Squeo
Keyword(s):  
Aluminum Alloy ◽  
Laser Welding ◽  
Aa 2024 ◽  
Laser Sources

Quality Assessment and Metallurgical Examination of Laser Welded Sheets

2009 ◽  
Vol 83-86 ◽  
pp. 611-615
Author(s):  
Numan Abu-Dheir ◽  
Bekir Sami Yilbas
Keyword(s):  
Laser Welding ◽  
Laser Power ◽  
Laser Scanning ◽  
Scanning Speed ◽  
Careful Examination ◽  
Welding Parameters ◽  
Weld Quality ◽  
Laser Weld ◽  
Power Intensity ◽  
Segregation Profile

Laser welding of steel 316L sheets is considered and the effects of laser welding parameters on the laser weld quality and metallurgical changes in the weld section are presented. The laser weld quality is assessed through careful examination of weld geometrical features, and the resulting weld microstructure. Metallurgical changes in the weld sites are examined using optical, and electron scanning microscope (SEM). Two levels of heat inputs are used-1500W and 2000W; and two scanning speeds of 2cm/s and 4cm/s are used to laser weld 316L sheets. It is found that at the high laser power intensities, evaporation takes place in the irradiated region and as the laser power intensity increases further, a cavity is formed at the top surface of the welding cross section. A similar situation is also observed as the laser scanning speed reduces. The low diffusivity of the alloying elements at high temperatures preserves the segregation profile. The scattered partitioning of the cells and dendrite boundaries are observed due to the presence of Cr and Mo.

Porosity Formation and Prevention in Pulsed Laser Welding

2006 ◽  
Vol 129 (8) ◽  
pp. 1014-1024 ◽  
Author(s):  
Jun Zhou ◽  
Hai-Lung Tsai
Keyword(s):  
Laser Welding ◽  
Molten Metal ◽  
Solidification Rate ◽  
Pulsed Laser ◽  
Deep Penetration ◽  
Pulse Profile ◽  
Porosity Formation ◽  
Pulsed Laser Welding ◽  
Laser Welds ◽  
Solidification Processes

Porosity has been frequently observed in solidified, deep penetration pulsed laser welds. Porosity is detrimental to weld quality. Our previous study shows that porosity formation in laser welding is associated with the weld pool dynamics, keyhole collapse, and solidification processes. The objective of this paper is to use mathematical models to systematically investigate the transport phenomena leading to the formation of porosity and to find possible solutions to reduce or eliminate porosity formation in laser welding. The results indicate that the formation of porosity in pulsed laser welding is caused by two competing factors: one is the solidification rate of the molten metal and the other is the backfilling speed of the molten metal during the keyhole collapse process. Porosity will be formed in the final weld if the solidification rate of the molten metal exceeds the backfilling speed of liquid metal during the keyhole collapse and solidification processes. Porosity formation was found to be strongly related with the depth-to-width aspect ratio of the keyhole. The larger the ratio, the easier porosity will be formed, and the larger the size of the voids. Based on these studies, controlling the laser pulse profile is proposed to prevent/eliminate porosity formation in laser welding. Its effectiveness and limitations are demonstrated in the current studies. The model predictions are qualitatively consistent with reported experimental results.

Effect of water depth on weld quality and welding process in underwater fiber laser welding

2017 ◽  
Vol 115 ◽  
pp. 112-120 ◽  
Author(s):  
Ning Guo ◽  
Xiao Xing ◽  
Hongyun Zhao ◽  
Caiwang Tan ◽  
Jicai Feng ◽  
...  
Keyword(s):  
Laser Welding ◽  
Fiber Laser ◽  
Water Depth ◽  
Welding Process ◽  
Weld Quality ◽  
Fiber Laser Welding ◽  
Effect Of Water
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