Prevention of macrodefects in squeeze casting of an Al-7 wt pct Si alloy

Abstract

The squeeze casting of an Al-7 wt pct Si alloy was carried out in order to investigate the conditions for the formation and the prevention of macrosegregation. The effects of process parameters such as applied pressure, die temperature, pouring temperature, delay time, degassing, and inoculation on the formation of macrosegregation were investigated, in correlation with the evolution of macrostructure and shrinkage defects. Three critical applied pressures were defined, based on the experimental results for the squeeze-cast Al-7 wt pct Si. The first is the critical applied pressure under which shrinkage defects form (P SC ). The second is the critical applied pressure above which macrosegregates form (P MS ). The third is the critical applied pressure above which and under which minor segregation forms. (P m and P MS , respectively). With the concept of these three critical pressures, an experimental diagram describing the optimum process conditions was proposed for obtaining sound squeeze castings. It was concluded that sound castings without macrosegregation and shrinkage defects can only be obtained when the applied pressure is in the range where P SC Ͻ P Ͻ P m (ϽP MS ). Both degassing and inoculation treatments greatly enhanced the soundness of the castings. It was also found that the pouring temperature and the delay time should not exceed T D-critical and t D-critical , respectively, in order to achieve sound castings.

Modelling in Squeeze Casting Process-Present State and Future Perspectives

“…The experiments performed by various researchers using classical engineering approach to study the effects of squeeze pressure, casting temperature, die temperatures, time delay, inoculants and pressure duration on solidification time, density, secondary dendrite arm spacing, grain size, hardness, tensile and impact strengths of different aluminium based alloys [48][49][50][51][52][53][54][55][56][57][58][59][60]. The following advantages and limitations have been identified from the above discussed literatures,…”

Multi-Objective Optimization of Squeeze Casting Process using Genetic Algorithm and Particle Swarm Optimization

“…In addition to the said approaches, the influence of casting temperature on mechanical properties was studied in [13] for the fixed die temperature, squeeze pressure and pressure durations. In [14], the effects of squeeze pressure, pouring temperature, die temperature, inoculants, degassing and time delay before pressurization on formation of macro defects with evolution of microstructures were investigated via classical engineering experimental approach. The above approach identified only main effect of the process variables and neglected the interaction factor effects completely.…”

Bending Strength and Fracture Investigations of Cu Based Composite Materials Strengthened with δ-Alumina Fibres

“…Recently pressure infiltration as a low cost, efficient and fast method are Brought to you by | MIT Libraries Authenticated Download Date | 5/10/18 1:41 PM frequently used for reinforcing castings in the most loaded regions. Among them squeeze casting as industry method can be easy adopted for production of composite materials characterised with low porosity, fine microstructure and good mechanical properties [5][6][7]. Though to infiltrate porous preform with Cu alloys new process parameters and construction of the mould should be elaborated to overcome problems with high temperature and rapid solidification of metal.…”