The Effects of Heat Treatment on the Microstructure and Tensile Properties of an HPDC Marine Transmission Gearcase

Abstract

The drive for continuously improving the performance and increasing the efficiencies of marine transportation has resulted in the development of a new alloy, Mercalloy A362™. This alloy was designed to lighten Mercury Marine’s lower transmission gearcase while also improving the alloy’s recyclability. The new prototype gearcase was subjected to Mercury Marine’s standard service conditions, which resulted in the premature failure of the prototype. A previous study revealed that a large accumulation of unwanted residual stress (~120 MPa) was present in the gearcase following the high pressure die casting process. Fortunately, the T5 heat treatment reduced the magnitude of stress by approximately 50%. However, the effects that the T5 heat treatment had on the microstructure and mechanical properties of the alloy were not discussed. Thus, this research article characterizes the effects that the T5 heat treatment has on the volume fraction and morphology of the intermetallics, as well as the tensile performance of the alloy. It was found that the T5 heat treatment led to only minor increases in the volume fraction of Fe-bearing intermetallics, leading to similar tensile properties in both the as-cast and T5 condition. These results suggest that the T5 heat treatment can alleviate residual stress without significantly altering the mechanical properties of the alloy. The results from the previous stress analysis and the current study were used to optimize the manufacturing process which led to the successful introduction of the gearcase into the competitive marine industry.

Mechanical Properties of a Structural Component Processed in High-Pressure Die Casting (HPDC) with a Non-Heat-Treated Aluminum Alloy

“…The shock towers did not show any defects caused by pre-solidification or shrinkage porosity, which are mainly caused by high temperature differences in solidification; this was a main concern due to the low percentage of silicon and the high temperature set up at the dosing furnace, as shown in Figures 8 and 9. The main defects detected in the mechanical property's samples were small porosities generated due to the process [20][21][22][27][28][29][30][31].…”

“…Aural thermal aluminum alloys have been developed as a solution for heat treatment temperatures around 500 • C, and can be combined with water quenching, and partial solution heat treatment at a slightly lower temperature, followed by rapid air cooling [20,21]. This alloy is designed to achieve greater ductility in F and T5 tempers.…”

Insight into the Properties of Novel Materials—Superalloys, Ferrous and Lightweight Alloys and Metal Matrix Composites

“…Although the prototype initially failed under standard service conditions due to accumulated residual stress, a T5 heat treatment mitigated this issue by reducing stress by approximately 50%. This research [5] investigated the effects of the T5 heat treatment on the alloy's intermetallic volume fraction, morphology, and tensile performance, revealing minor changes in intermetallics, but similar tensile properties in both the as-cast and T5 conditions. The combination of stress analysis and this study's findings optimized the manufacturing process, successfully introducing the gearcase into the competitive marine industry.…”

“…This Special Issue presents a curated collection of five research papers [1][2][3][4][5] focusing on diverse aspects of new material development. These aspects encompass the characterization of material properties, fitness-for-service assessments for various applications, implementation, and production processes.…”

An Acoustic Emission Method for Assessing the Degree of Degradation of Mechanical Properties and Residual Life of Metal Structures under Complex Dynamic Deformation Stresses

“…An analysis of the existing methods and means for determining the degradation of the mechanical properties of materials during the operation of structures in real time showed that they are all intended for the study of one type of deformation: tension [ 37 , 38 , 39 ] or bending [ 40 , 41 , 42 , 43 ], while under real conditions loading forces act on the material, under combined conditions of deformation [ 44 , 45 , 46 , 47 , 48 , 49 , 50 ].…”