Font Size: a A A

Sc,Zr Composited Microalloying And Microstructure And Properties Of Al-Si-Mg-Cu Alloy After Isothermal Compression Deformation

Posted on:2019-04-10Degree:MasterType:Thesis
Country:ChinaCandidate:Y ZhangFull Text:PDF
GTID:2381330602456657Subject:Materials engineering
Abstract/Summary:PDF Full Text Request
Al-Si alloys have been widely used in the field of production because of their good casting properties.The deformation ability of general Al-Si alloys is weak,and the deformation strengthening is an important means to strengthen aluminum alloys.In this paper,the use of Sc,Zr composite microalloying,and its isothermal compression treatment and solution treatment,to control the sub-structure of aluminum alloys and aging precipitation phase,which has important research meaning to improve the performance of the alloy.In this paper,a conventional ingot metallurgical method was used to prepare the Al-Si-Mg-Cu alloy of Sc and Zr.The effect of Sc and Zr on the microstructures and mechanical properties of as-cast and T6 state were investigated based on optical microscopy,electron back-scatter,transmission electron microscope,tensile tests and hardness tests.The microstructure and properties of Al-Si-Mg-Cu alloy after Sc,Zr composited micro-alloying and isothermal compression deformation were investigated.The experimental results showed that the addition of Sc and Zr can significantly improve the as-cast microstructure and improve the mechanical properties.The Zr content is 0.20%.When the content of Sc is increased to 0.60%,a large number of dimples appear in the grain and the structure is equiaxed and get the best performance,the hardness,tensile strength and elongation after breaking were 80.9HBS,260.5MPa and 9.6%.The alloy Al-3.0Si-0.45Mg-0.45Cu-0.2Zr-0.4Sc,and isothermally compressed at a maximum temperature of 350℃,a minimum strain of 0.4?10-3S-1,we find that the alloy has obvious dynamic recrystallization.With the decrease of strain rate of the same strain,the number of undistorted recrystallized grains in the alloy increases and grows at a higher temperature,which promotes the dynamic recovery and recrystallization of the alloy.with the increase of temperature,improve the kinematic capacity of the alloy substructure,and promote the dynamic recovery alloy and recrystallization.Tensile strength reaches a maximum value of 325.1 Mpa at a temperature of 250°C and a strain rate of 0.4?10-1S-1,as a result of temperature and strain rates affecting the atomic activity,which in turn affects the migratory ability of substructures such as dislocations.The solid solution treatment of the experimental alloy before the compression deformation is also beneficial to the improvement of the tensile strength of the alloy.After the solution treatment,the second phase particles Al3(Sc,Zr)phase and Mg2Si precipitation limited metastructural movement during the isothermal compression process,especially the finely dispersed Al3(Sc,Zr)phase,strongly pinning dislocations,played the role of precipitation strengthening and inhibition of recrystallization.At T=250℃,ε?=0.4?10-2 S-1,the maximum value of tensile strength was 344.6Mpa,which exceeded the tensile strength of the hot-deformed alloy without solution treatment.
Keywords/Search Tags:Sc,Zr composited microalloying, Isothermal compression, Sub-structure, Second phase particles, Mechanical properties
PDF Full Text Request
Related items