Research On Microstructure Evolution And High Temperature Mechanical Properties Of Al-Si-Cu-Mn-Fe Alloy For Diesel Engine

With the rapid development of transportation fields,the traditional diesel engine is developing towards the direction of large thrust weight ratio and low fuel consumption,which requires the higher heat resistance of aluminum alloy cylinders.In addition,in order to adapt to the green development trend of energy conservation and emission reduction,the recovery and utilization of recycled aluminum has been become one of the important directions to develop the aluminum industry.The iron-rich phases in recycled aluminum alloy are beneficial to the improvement of heat resistance mechanical properties.Therefore,the development of high strength,toughness and heat-resistant aluminum alloy based on recycled aluminum alloy is not only to provide the theoretical basis and technical guidance for the development of high-power diesel engine cylinder block materials,but also to promote energy conservation and emission reduction in the field of casting and realize the green manufacturing.In this article,the Al-Si-Cu-Mn-Fe alloys with high iron content as the research object,which combines alloying and changing the forming processes.The effect of Ti,Cu content and different forming processes on the microstructure and mechanical properties of alloys are systematically investigated,by using OM,SEM,TEM,and tensile properties testing etc methods.The conclusions are as followed:The effects of different Ti and Cu contents on the microstructure and mechanical properties of the heat-treated gravity casting Al-Si-Cu-Mn-Fe alloy have been studied.With the increase of Ti and Cu content,the room temperature and high temperature mechanical properties of the heat-treated gravity die cast Al-Si-Cu-Mn-Fe alloys have been gradually improved,and their mechanical properties are better than the other industrial applications of heat-resistant aluminum alloys.This is mainly due to the grain refinement and dispersion strengthening.However,the excessive Ti content does not improve the room temperature and high temperature mechanical properties of the alloy,which is mainly due to the increase in porosities and needle-like?-Fe?Al₇Cu₂Fe?and Ti Al Si phases.The effects of different Ti and Cu contents on the microstructure and mechanical properties of the heat-treated squeeze cast Al-Si-Cu-Mn-Fe alloy have been studied.Compared with gravity casting alloy,the squeeze casting alloy has more excellent tensile mechanical properties at room temperature.When the thermal exposure time is 0.5 h,the high temperature mechanical properties of squeeze casting alloys are significantly higher than those of gravity cast alloys.With the increase of the thermal exposure time,the high temperature mechanical properties of the alloys are similar under the two forming processes.This is mainly due to the grain refinement of squeeze-cast alloys and grain boundary slip at high temperatures.The effects of different Ti and Cu contents on the microstructure and mechanical properties of heat-treated semi-solid thixoforming Al-Si-Cu-Mn-Fe alloys have been studied.The room temperature mechanical properties of semi-solid thixoforming alloys are slightly lower than those of squeeze cast alloys.However,their high temperature mechanical properties are significantly higher than those of the gravity die cast and squeeze cast alloys.This is mainly due to the synergistic strengthening of the precipitation strengthening and grain boundary strengthening of the thermally stable intermetallic compound phases,as well as the appropriate grain size.