The Effects of Solidification Cooling Rates on the Mechanical Properties of an Aluminum Inline-6 Engine Block

Evolution of residual stress through the processing stages in manufacturing of bore-chilled sand-cast aluminum engine blocks with pressed-in iron liners

“…2, the strain charts are presented in order of the manufacturing process. The high solidi cation cooling rate of the cylinder bridge material (~5-14°C/s), as reported by Stroh et al [10] and caused by the integration of the thermally-massive bore chills, led to the evolution of compressive strains (i.e., negative strain) for all three orientations of strain (i.e., axial, radial, and hoop) along the entire depth of the cylinder bridge of the TSR + Chills block. C. Dong et al [18] found that increasing the cooling rate from 0.5°C/s to 40°C/s led to an increase of the compressive stress in their alloy from approximately -200 MPa to -400 MPa.…”

“…Garat [22] suggest a slightly lower stress of about 20-30 MPa. Regardless of the exact value, even with the combined contribution of operational and residual stress, the magnitude of tensile stress in the cylinder bridge is still well below the materials as-cast yield strength of ~ 205 MPa [10].…”

“…Fortunately, the radial strain decreases nearly linearly in magnitude with increasing depth along the cylinder bridge. One of the main reasons for the gradual decrease in the magnitude of radial strain from the 6 to 42 mm position is the tapered wall thickness of cylinder bridge (i.e., ~10 mm and 19 mm at the top and bottom, respectively) which is incorporated to facilitate the extraction of the steel chill after the casting process [10]. The larger wall thickness at the bottom of the cylinder bridge permits a greater distribution of the forces at this location, as compared to the top, and therefore results in the observed decrease in strain.…”

“…To combat the issues related to residual stress and insu cient/inconsistent mechanical properties, automotive manufacturers, such as Nemak, have begun introducing new methods for increasing the solidi cation cooling rates, minimizing gas entrapment during casting, and re ning the microstructure of their alloys. For example, in a previous study conducted by the authors, Stroh et al [10] investigated the effects that two process modi cations (i.e., eliminating the cast-in liners from the casting process and integrating cylinder bore chills) has on the solidi cation cooling rates and tensile properties of the cylinder bridge material in an as-cast inline, six-cylinder Al engine block. The study found that the use of bore chills during the production of the I6 engine block led to a more re ned microstructure and homogenized the mechanical properties along the entire depth of the cylinder bridge, as compared to the cylinder bridge of the V6 engine block described by Lombardi [11].…”

Performance Analysis of Metaheuristic Optimization Algorithms in Estimating the Interfacial Heat Transfer Coefficient on Directional Solidification

“…An aluminum-based alloy was the material chosen to be analyzed. This type of alloy has a notorious importance, since, in an effort to improve vehicle fuel efficiency by lower consumption, lightweight aluminum alloys have been replacing other materials for use in automotive integrated systems and components [23] such as engine blocks and cylinder heads [51] and also on aerospace and marine applications [28]. Among aluminum-based alloys, the aluminum-silicon (Al-Si) system has considerable prestige.…”