The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and...The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.展开更多
The effects of Si content on the microstructure and yield strength of Al-(1.44-12.40)Si-0.7 Mg(wt.%)alloy sheets under the T4 condition were systematically studied via laser scanning confocal microscopy(LSCM),DSC,TEM ...The effects of Si content on the microstructure and yield strength of Al-(1.44-12.40)Si-0.7 Mg(wt.%)alloy sheets under the T4 condition were systematically studied via laser scanning confocal microscopy(LSCM),DSC,TEM and tensile tests.The results show that the recrystallization grain of the alloy sheets becomes more refined with an increase in Si content.When the Si content increases from 1.44 to 12.4 wt.%,the grain size of the alloy sheets decreases from approximately 47 to 10μm.Further,with an increase in Si content,the volume fraction of the GP zones in the matrix increases slightly.Based on the existing model,a yield strength model for alloy sheets was proposed.The predicted results are in good agreement with the actual experimental results and reveal the strengthening mechanisms of the Al-(1.44-12.40)Si-0.7 Mg alloy sheets under the T4 condition and how they are influenced by the Si content.展开更多
Effects of natural aging and test temperature on the tensile behaviors have been studied for a highperformance cast aluminum alloy Al–10Si–1.2Cu–0.7Mn. Based on self-strengthening mechanism and spheroidization micr...Effects of natural aging and test temperature on the tensile behaviors have been studied for a highperformance cast aluminum alloy Al–10Si–1.2Cu–0.7Mn. Based on self-strengthening mechanism and spheroidization microstructures, the alloy tested at room temperature（RT） exhibits higher 0.2% proof stress（YS） of 206 MPa, ultimate tensile strength（UTS） of 331 MPa and elongation of 10%. Increasing aging time improves the YS and UTS and reduces the ductility of the alloy. Further increasing aging time beyond72 h does not signi？cantly increase the tensile strengths. Increasing test temperature significantly decreases the tensile strengths and increases the ductility of the alloy. The UTS of the alloy can be estimated by using the hardness. The Portevin–Le Chatelier effect occurs at RT due to the interactions between solid solution atoms and dislocations. Similar behaviors occurring at 250℃ are attributed to dynamic strain aging mechanism. Increasing aging time leads to decrease in the strain-hardening exponent（n） value and increase in the strain-hardening coeficient（k） value. Increasing test temperature apparently decreases the n and k values. Eutectic phase particles cracking and debonding determine the fracture mechanism of the alloy. Final failure of the alloy mainly depends on the global instability（high temperature, necking） and local instability（RT, shearing）. Different tensile behaviors of the alloy are mainly attributed to different matrix strengths, phase particle strengths and damage rate.展开更多
基金Project(51274245) supported by the National Natural Science Foundation of China
文摘The microstructural evolution and mechanical properties of Al-18 Si-4 Cu-0.5 Mg alloy modified by the addition of La-Ce rare earth elements through OM,SEM,EPMA and tensile tests were investigated.The results of OM and SEM analyses indicated that primary Si particles were significantly refined from coarse block-like and irregular polygonal shapes into fine flaky shapes,while eutectic Si particles were modified from coarse and needle-like into fine and rod-or coral-like shapes with increase of La-Ce addition.The alloy exhibited the minimum primary Si particle size and the best mechanical properties with the addition of 0.3 wt.%La-Ce.The average particle size decreased from 61 to 28 μm,the ultimate tensile strength increased from 222 to 242 MPa and the elongation increased from 3.2% to 6.3%.In addition,modification mechanisms and fracture modes were explored by the means of SEM and EPMA.
基金Project(2016YFB0300801)supported by the National Key Research and Development Program of ChinaProject(51871043)supported by the National Natural Science Foundation of ChinaProject(N180212010)supported by the Fundamental Research Funds for the Central Universities of China。
文摘The effects of Si content on the microstructure and yield strength of Al-(1.44-12.40)Si-0.7 Mg(wt.%)alloy sheets under the T4 condition were systematically studied via laser scanning confocal microscopy(LSCM),DSC,TEM and tensile tests.The results show that the recrystallization grain of the alloy sheets becomes more refined with an increase in Si content.When the Si content increases from 1.44 to 12.4 wt.%,the grain size of the alloy sheets decreases from approximately 47 to 10μm.Further,with an increase in Si content,the volume fraction of the GP zones in the matrix increases slightly.Based on the existing model,a yield strength model for alloy sheets was proposed.The predicted results are in good agreement with the actual experimental results and reveal the strengthening mechanisms of the Al-(1.44-12.40)Si-0.7 Mg alloy sheets under the T4 condition and how they are influenced by the Si content.
基金supported by the Project Funded by China Postdoctoral Science Foundation(No.2015M571562)
文摘Effects of natural aging and test temperature on the tensile behaviors have been studied for a highperformance cast aluminum alloy Al–10Si–1.2Cu–0.7Mn. Based on self-strengthening mechanism and spheroidization microstructures, the alloy tested at room temperature（RT） exhibits higher 0.2% proof stress（YS） of 206 MPa, ultimate tensile strength（UTS） of 331 MPa and elongation of 10%. Increasing aging time improves the YS and UTS and reduces the ductility of the alloy. Further increasing aging time beyond72 h does not signi？cantly increase the tensile strengths. Increasing test temperature significantly decreases the tensile strengths and increases the ductility of the alloy. The UTS of the alloy can be estimated by using the hardness. The Portevin–Le Chatelier effect occurs at RT due to the interactions between solid solution atoms and dislocations. Similar behaviors occurring at 250℃ are attributed to dynamic strain aging mechanism. Increasing aging time leads to decrease in the strain-hardening exponent（n） value and increase in the strain-hardening coeficient（k） value. Increasing test temperature apparently decreases the n and k values. Eutectic phase particles cracking and debonding determine the fracture mechanism of the alloy. Final failure of the alloy mainly depends on the global instability（high temperature, necking） and local instability（RT, shearing）. Different tensile behaviors of the alloy are mainly attributed to different matrix strengths, phase particle strengths and damage rate.
