Study On Sc Microalloying And Heat Treatment Of ZL205A Alloy

Using aluminum instead of steel is an important means to realize automobile lightweight,which can greatly reduce the quality of automobile parts,save energy,reduce cost and environmental pollution.ZL205A al oy has high strength,but its plastic index is difficult to meet the requirements of high-performance automobile structural parts.The effect of rare earth scandium on the microstructure and properties of ZL205A al oy was studied.In this paper,rare earth element scandium microalloying was carried out on ZL205A al oy.The effect of rare earth scandium on the microstructure and properties of ZL205A al oy was studied.And two new type of multi-stage solid solution treatment process T46-40?546?+540??and T44-41?544?+541??are developed.The microstructure and properties of ZL205A aloy under the new heat treatment processes of T46-40 and T44-41 were studied.The grain size first decreases,then increases and then decreases with the increase of rare earth scandium content in ZL205A al oy.There are two kinds of rare earth scandium phase in the al oy,which are particle rare earth phase AlCu₂Sc phase and block rare earth phase AlScZrTi phase.The part of the particle phases in the stress concentration can occur as a whole fracture dislocation and relaxation product group when amount AlCu₂Sc particle phases remain around the grain boundary.And the elongation of al oy will be greatly to strengthen,al oy mechanical properties of?_b=460 MPa,?=11%.However,the AlScZrTi cube phases of have obvious splitting effect on the al oy matrix,witch will reduce the mechanical properties of the al oy greatly.Single-stage short-term high temperature solid solution treatment of 544? and 546? can't avoid overheating defects when the solid solution of?phase is complete.Once the overheating defect appears,it is difficult to eliminate.Both multistage solid solution processes of T46-40 and T44-41 can achieve great solid solution effect.The solid solution efficiency of T46-40 is faster and the process requirements of T46-40 are stricter.The stability of T44-41 is better,and the process window of T44-41 is wider.Under the aging process of T5,the al oy performance can be achieved as follows:?_b=480 MPa,?=10%of T46-40 and?_b=450 MPa,?=11.2%of T44-41.