scholarly journals Generation and Relaxation of Residual Stresses in Automotive Cylinder Blocks

2020 ◽  
Author(s):  
Serageldin Salem Mohamed ◽  
Agnes M. Samuel ◽  
Herbert W. Doty ◽  
Salvador Valtierra ◽  
Fawzy H. Samuel
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
Solution Heat Treatment ◽  
Cold Water ◽  
Solidification Rate ◽  
Industrial Applications ◽  
Air Cooling ◽  
Dendrite Arm Spacing ◽  
Cylinder Length ◽  
Engine Blocks

There is direct proportionality between ultimate tensile stress (UTS) and residual stresses (RS). Residual stresses gradually decrease with decreasing cooling/quenching rates. Quenching in cold water develops highest, whereas air cooling produces lowest, residual stresses. Significant increase in RS is observed in specimens with low dendrite arm spacing (high solidification rate), while lower residual stresses are measured in specimens with high dendrite arm spacing (low solidification rate). For I-4 and V-6 engine blocks, there is refinement in microstructure due to the increase in solidification rate along the cylinder length. The developed residual stresses are normally tensile in both engine types. Air cooling following solution heat treatment produces higher RS compared to warm water and cold water quenching. Solution heat treatment and freezing lead to maximum RS relaxation where 50% of the stresses are reduced after the solution heat treatment step. Aging time and temperature are directly proportional to the residual stresses relaxation. Relaxation of RS also depends on the geometry and size of the workpiece. It should be mentioned here that the I-4 and V-6 cylinder blocks were provided by Nemak-Canada (Windsor-Ontario-Canada). Residual stress measurements technique and procedure are typical of those used by the automotive industry in order to provide reliable data for industrial applications supported by intensive experiments.

scholarly journals Microstructure and Residual Stresses of AA2519 Friction Stir Welded Joints under Different Heat Treatment Conditions

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 834
Author(s):  
Lucjan Śnieżek ◽  
Robert Kosturek ◽  
Marcin Wachowski ◽  
Bogusz Kania
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
Welded Joints ◽  
Precipitation Hardening ◽  
Cold Water ◽  
Traverse Speed ◽  
Welding Parameters ◽  
X Ray ◽  
Friction Stir ◽  
Treatment Conditions

The aim of this research was to investigate the effect of different heat treatment conditions of AA2519 friction stir welded joints on their microstructure and residual stresses. The following welding parameters have been used: 500 rpm tool rotation speed, 150 mm/min tool traverse speed, tool tilt angle 2°, pressure force 17 kN. The welded material was investigated in three different configurations: HT0, HT1, and HT2. The first type of weld (HT-0) was made using AA2519 alloy in non-precipitation hardened state and examined in such condition. The second type of weld (HT-1) has been performed on AA2519-T62, that corresponds to precipitation hardening condition. The last type of weld (HT2) was performed on annealed AA2519 and the obtained welds were subjected to the post-weld precipitation hardening process. The heat treatment was carried out in two stages: solution heat treatment (530 °C/2 h + cooling in cold water) and aging (165 °C/1 0 h). Residual stresses were measured using X-Ray diffraction patterns obtained from Bruker D8 Discover X-ray diffractometer utilizing the concepts of Euler cradle and polycapillary primary beam optics. The conducted research indicates that the best material properties: homogenous microstructure and uniform distribution of microhardness and compressive state of residual stresses were obtained for the HT-2 series samples subjected to heat treatment after the friction stir welding (FSW) process.

scholarly journals Mitigation of cylinder distortion in aluminum alloy engine blocks via heat treatment process optimization

2021 ◽  
Author(s):  
Anthony Lombardi
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Neutron Diffraction ◽  
Solution Heat Treatment ◽  
Treatment Process ◽  
Tensile Residual Stress ◽  
Engine Block ◽  
Engine Blocks ◽  
In Situ Neutron Diffraction

Lightweighting has become an important factor in the automotive industry due to stringent government regulations on fuel consumption and increased environmental awareness. Aluminum alloys are 65% lighter than cast iron enabling significant weight reduction. However, there are several significant challenges associated to the use of hypoeutectic Al-Si alloys in engine block applications. This dissertation investigated the factors influencing the susceptibility of in-service cylinder distortion as it is deleterious to engine operating efficiency, leading to environmental (increased carbon emissions) and economic (expensive recalls) repercussions. The initial segment of this dissertation sought to quantitatively confirm the cause of cylinder distortion by investigating distorted and undistorted service tested engine blocks. This analysis involved measurement of macro-distortion using a co-ordinate measuring machine, in-depth microstructural analysis, measurement of tensile properties, and residual stress mapping along the length of the cylinder bores (neutron diffraction). Upon determining the cause of distortion, the second phase of this project optimized the solution heat treatment parameters to mitigate future distortion in the engine blocks. This optimization was carried out by varying heat treatment parameters to maximize engine block strength. In addition, a pioneering application of in-situ neutron diffraction, along with a unique engine heating system, was used to develop a time-dependent correlation of residual stress relief during heat treatment, assisting in process optimization. The results indicate that the distorted engine block had high tensile residual stress, specifically at cylinder depths greater than 30 mm, while the undistorted block had mainly compressive stress. The maximum distortion occurred near the center portion of the cylinder (~60 mm), which had a combination of coarse microstructure (lower strength) and high tensile residual stress. As such,distortion can be prevented via maximization of strength and reduction in tensile residual stress. Lab scale castings and in-situ neutron diffraction were used to successfully develop an optimal heat treatment process to increase engine block integrity. These experiments found that solution heat treatment at 500 °C for 2 h increased tensile yield strength by 15-20% over engines produced using the current process. Furthermore, tensile residual stress was completely relieved by this heat treatment, reducing the susceptibility to in-service distortion. Solutionizing at temperatures above 500 °C was deemed unsuitable for engine block production due to incipient melting, which deteriorates strength.

A Novel Experimental Design to Obtain Forming Limit Diagram of Aluminium Alloys for Solution Heat Treatment, Forming and In-Die Quenching Process

2014 ◽  
Vol 622-623 ◽  
pp. 241-248 ◽  
Author(s):  
Zhu Tao Shao ◽  
Qian Bai ◽  
Jian Guo Lin
Keyword(s):  
Heat Treatment ◽  
Solution Heat Treatment ◽  
High Efficiency ◽  
Biaxial Tension ◽  
Forming Limit ◽  
Air Cooling ◽  
Connecting Rod ◽  
Form Complex ◽  
Die Quenching ◽  
Strain Paths

Solution heat treatment, forming and in-die quenching (HFQ) is a patented process to form complex shape metal components at a high efficiency and a low cost. Conventional experiment approaches to determine forming limit curves (FLCs) at different strain paths are not applicable for the HFQ forming process. A novel biaxial tensile test rig is designed to overcome the difficulties and determine the FLCs at high temperatures based on the commercial Gleeble machine. This test device employs the circle plate and connecting rod mechanism in order to achieve different strain states, such as uniaxial tension, plane strain and biaxial tension. Resistance heating and air cooling are adopted to obtain an isothermal environment and to control cooling rates in Gleeble respectively. The designs of the cruciform specimen for this test are also introduced in this paper.

TEM Investigations of Electron 21 Magnesium Alloy

2007 ◽  
Vol 130 ◽  
pp. 175-180 ◽  
Author(s):  
Andrzej Kiełbus
Keyword(s):  
Heat Treatment ◽  
Magnesium Alloy ◽  
Solution Heat Treatment ◽  
Cast Alloy ◽  
Solution Treatment ◽  
Air Cooling ◽  
Transmission Electron ◽  
The Matrix ◽  
Cast Condition ◽  
Cast Microstructure

The paper presents results of TEM investigations of Elektron 21 magnesium alloy in as cast condition and after heat treatment. The compositions of the Elektron 21 alloy used in the present study was Mg-2,7%wtNd-1,2%wtGd-0,47%wtZr. Solution heat treatment was performed at 520°C/8 h/water. Ageing treatments were performed at 200°C/4÷96h and 300°C/48h with cooling in air. The as-cast microstructure and microstructural evolution during heat treatment were examined by transmission electron microscopy. Samples were prepared using Gatan PIPS ion mill. Examinations were performed in a JEM 2010 ARP microscope. The microstructure of the cast alloy consists of a-Mg phase matrix with precipitates of Mg12(Ndx,Gd1-x) phase at grain boundaries. After solution treatment the Mg12(Ndx,Gd1-x) phase dissolved in the matrix. The ageing treatment applied after solution treatment with air-cooling caused precipitation of a β’ and β phases.

scholarly journals Mitigation of cylinder distortion in aluminum alloy engine blocks via heat treatment process optimization

2021 ◽  
Author(s):  
Anthony Lombardi
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Neutron Diffraction ◽  
Solution Heat Treatment ◽  
Treatment Process ◽  
Tensile Residual Stress ◽  
Engine Block ◽  
Engine Blocks ◽  
In Situ Neutron Diffraction

Lightweighting has become an important factor in the automotive industry due to stringent government regulations on fuel consumption and increased environmental awareness. Aluminum alloys are 65% lighter than cast iron enabling significant weight reduction. However, there are several significant challenges associated to the use of hypoeutectic Al-Si alloys in engine block applications. This dissertation investigated the factors influencing the susceptibility of in-service cylinder distortion as it is deleterious to engine operating efficiency, leading to environmental (increased carbon emissions) and economic (expensive recalls) repercussions. The initial segment of this dissertation sought to quantitatively confirm the cause of cylinder distortion by investigating distorted and undistorted service tested engine blocks. This analysis involved measurement of macro-distortion using a co-ordinate measuring machine, in-depth microstructural analysis, measurement of tensile properties, and residual stress mapping along the length of the cylinder bores (neutron diffraction). Upon determining the cause of distortion, the second phase of this project optimized the solution heat treatment parameters to mitigate future distortion in the engine blocks. This optimization was carried out by varying heat treatment parameters to maximize engine block strength. In addition, a pioneering application of in-situ neutron diffraction, along with a unique engine heating system, was used to develop a time-dependent correlation of residual stress relief during heat treatment, assisting in process optimization. The results indicate that the distorted engine block had high tensile residual stress, specifically at cylinder depths greater than 30 mm, while the undistorted block had mainly compressive stress. The maximum distortion occurred near the center portion of the cylinder (~60 mm), which had a combination of coarse microstructure (lower strength) and high tensile residual stress. As such,distortion can be prevented via maximization of strength and reduction in tensile residual stress. Lab scale castings and in-situ neutron diffraction were used to successfully develop an optimal heat treatment process to increase engine block integrity. These experiments found that solution heat treatment at 500 °C for 2 h increased tensile yield strength by 15-20% over engines produced using the current process. Furthermore, tensile residual stress was completely relieved by this heat treatment, reducing the susceptibility to in-service distortion. Solutionizing at temperatures above 500 °C was deemed unsuitable for engine block production due to incipient melting, which deteriorates strength.

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