Computationally Optimized Homogenization Heat Treatment of Metal Alloys
A computational approach has been developed to improve the homogenization heat treatment of solid substitutional alloys. The method utilizes computational thermodynamics to determine a stepped approach to achieve optimal homogenization of the metal alloy, resulting in improved materials and processing costs. In addition, the approach allows the homogenization process to be ‘tuned’ for the intended use of the alloy. This technology is available for licensing and/or further collaborative research with the U.S. Department of Energy’s National Energy Technology laboratory.Description
Alloys are metallic solid solutions of two or more elements. During the casting or solidification of an alloy, the component elements typically segregate unevenly throughout the alloy. These chemical segregations or nonuniformities negatively impact an alloy’s mechanical properties such as corrosion/oxidation resistance, tensile strength, service temperature and hot workability. Unless used in the cast form, redistribution of the alloying elements is necessary to achieve optimal alloy performance. This requires a thermal process known as homogenization. Homogenization heat treatment results in the diffusion and redistribution of the alloying elements throughout the alloy. Other than altering chemical composition, homogenization is the primary means of ‘tuning’ an alloy for its intended use. The extent of homogenization directly determines the performance properties of the alloy.
Conventional homogenization processes require much experimentation. This usually entails numerous samples, substantial furnace time and associated energy, and additional lab time to physically evaluate the extent of homogenization. This is both a costly and time-consuming process. Thus, there is significant need to optimize the homogenization process for efficiency and cost effectiveness. To address this issue, NETL researchers developed a computationally-based approach to homogenization heat treatment of metal alloys.
The novel method utilizes thermodynamic simulation to determine the specific distribution/arrangement (i.e., the microsegregation) of alloying elements in the cast alloy. This is accomplished using the Scheil module of Thermo-Calc software. The determined microsegregation profiles are read into DICTRA kinetic modeling software to simulate elemental diffusion during homogenization heat treatment. ‘Heating’ takes place at a temperature below that at which the alloy initially begins to melt (i.e., the incipient temperature, Timp). Importantly, as an alloy’s microsegregation profile becomes more uniform, its Timp increases. This allows the homogenization heat treatment to be repeated, taking into account the ever-increasing Timp, until a desired level of homogeneity is achieved. Significantly, such a stepped approach to homogenization saves time. The result is the design of a homogenization strategy that when implemented under real conditions, provides optimal results in hours, not days.Benefits
• Reduction in energy consumption and carbon dioxide output due to shorter, more effective heat treatments
• Substantially lower processing costs
• Ability to optimize the mechanical properties of alloys for improved downstream performance
• Adaptable to the constraints of individual production facilities and the level of homogenization desiredApplications and Industries
• Any solid substitutional alloy utilized in a variety of industries, including, but not limited to aerospace, military, petrochemical, power generation, nuclear, structural, automotive and instrumentationTechnology Status
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