Energy Efficient Heat Treatment for Linerless Hypereutectic Al-Si Engine Blocks Made Using Vacuum HPDC Process

Abstract

Heat treatment standards developed by the aluminum industry over the last several decades are often not well optimized when applied to components cast by high cooling rate processes such as High Pressure Die Casting (HPDC), Low Pressure Permanent Mold (LPPM), Squeeze Casting, etc. The inherently finer as-cast structures should not require long solution times for the effective dissolution of intermetallic phases and the adequate thermal modification of structural constituents. Hence, long and expensive T6 and T7 treatments should not be required. Heat treatment studies involving as-cast laboratory samples with SDAS = 13.6 lm (equivalent to a thick-section HPDC casting) were conducted. Traditional and modified solution and aging treatments were compared. These studies suggest that a reduction of up to 92% in thermal processing time is possible while maintaining and/or improving the cast componentÕs metallurgical characteristics including hardness ( ‡75 HRB), dissolution of secondary phases, and spheroidization of the eutectic Si as well as overall homogeneity. Vacuum HPDC of an actual hypereutectic Al-20%Si motorcycle engine block confirmed the potential for significantly reduced heat treatment times, energy consumption, and overall costs.Keywords Al-Si hypereutectic alloy, heat treatment, non-equilibrium thermal analysis, physical simulations of metallurgical processes, primary Si, secondary dendrite arm spacing, vacuum High Pressure Die Casting (HPDC)

Review of measures for improved energy efficiency in production-related processes in the aluminium industry – From electrolysis to recycling

“…For components cast by processes with high cooling rates, for example high pressure die casting and low pressure permanent mould, the heat treatment standards are often not well optimised [83]. The long and expensive T6 and T7 treatments should not be needed, due to the inherently finer as-cast structures [83]. Modified versions of T4, T5 and T6 treatments can be used instead [83].…”

“…The long and expensive T6 and T7 treatments should not be needed, due to the inherently finer as-cast structures [83]. Modified versions of T4, T5 and T6 treatments can be used instead [83]. These can provide reductions in energy use and overall costs as well as lowering the processing time by 68-92% [83].…”

Fatigue in a heat treatable high silicon containing aluminium alloy

“…Hypereutectic Al-Si alloys are used in applications in which resistance to wear is adamant, due to the presence of primary silicon crystals, nevertheless these crystals pose a machinability problem for engine plants, and may not be able to comply with the rigorous static and dynamic mechanical properties demanded by the use in engine blocks [5][6][7][8][9][10]. The defects that are present in cast aluminium alloys affect their resistance to fatigue; the flaws that exert the higher influence are pores, either due to shrinkage or gas evolution, hard components of eutectic aggregates, intermetallic inclusions and precipitated particles, as cracks nucleate on the defects and grow following paths in which other smaller faults are concentrated [11][12][13][14][15][16][17][18][19][20][21][22].…”

In Situ Study of Microstructure Evolution in Solidification of Hypereutectic Al-Si Alloys with Application of Thermal Analysis and Neutron Diffraction

“…[14] Further optimization of heat treatment processing enabled development of energy efficient tempering routes. [15] Since adequate refinement of the primary Si crystals is of key importance and creates a technological challenge particularly during casting manufacturing, microstructure control methods represent a key research theme. [16] Currently, the scientific focus is on refinement of the primary Si crystals achieved by controlled alloying, addition of master alloys, and rapid solidification.…”