The Effect Of Properties Of Zn-Al Alloy With Adding Multiple Alloys

The ZA27 alloys used in the article are prepared from ZA27 alloy by adding Si and RE with same Ni-Ti.The solidification microstructure,the form and the distribution of the resultant,mechanical properties,friction wear properties of ZA27 alloy after adding Si and RE have been investigated by using Optical Microscope(OM),Scanning Electron Microscope(SEM),Electron Probe Microanalyzer(EPMA) and other modern equipments.The natures and mechanism of these characteristics have been analyzed.The analyse results of ZA27 alloy microstructure after adding Si and RE indicate that the element main exist in ZA27 alloy in the form of rich-Si phase,after adding Si and RE the crystal is fined well,more hard phases with the fine sizes and the apparent passivating shapes on the end were precipitated;The Si phase exist in ZA27 alloy in the form of Si particles,the Si particles are near sphere,and distribute uniformity.RE phase exists in ZA27 alloy the continuity of the separated phases are good.RE particles are fined and distribute more uniformity.RE is distributed between in grains and interdendrite.From its appearance,most of them are massive,grain and few of them is star shape,when the content grows,it is aggregated to stripe and massive shape,some of them is intersected in grains.The analyse of the mechanical performance indicates that,the tensile strength and elongation becomes lower,whereas,the hardness value grows firstly then drops.When adding2.7wt%Si and 0.08wt%RE,tensile strength and elongation are improved to 359MPa and 3.1%.When adding with 3.5wt%Si and 0.14wt%RE,the hardness value is 126HB,which is improved to 8.6%campared with matri alloy.The analyse of the SEM of the tensile fracture surface show that the fracture mechanism is a mix type fracture, the plastic fracture and the brittle fracture are coexistence.Oil sliding wear tests at room temperature show that the wear resistance of the alloy with Si and RE is superior to that of its matrix alloy.When adding 3.5wt%Si and 0.14wt%RE,the wearing stability and the wearing resistance of the alloy is improved campared with the alloys without treatment.With the increase of load,the wear loss weight,friction coefficient are all increased,the stability decreased.The wearing loss weigh reduced,friction coefficient minishen,the stability enhanced.The analyse of the wear surface indicate that in the oil sliding wear,in low loads,the wear mechanism is abrasion wear,with the loads increase,the abrasion wear weakened gradually, adherence increased,in larger load,the wear mechanism is adherence wear and abrasion wear.After solidication and aging,the micostructure and mechanical properties are getting better.With the prolong of aging time,micostructure is changing form featherlike finer laminate structure to coarser laminate structure and granular grain. When aging temperature is 100℃,the wearing loss becomes less,and with the aging time becomes longer,the wearing properties become better.After 6 hours aging time, the alloys of Si:3.5wt%,RE:0.14wt%wearing capacity are lower with aging compared with the alloys without treatment under the loan of 300N,600N,900N,which are to 24%,21%,25%respectively.The hardness value improves to 136HB.The alloys adding Si:2.7wt%,RE:0.08wt%,whose tensile strength and elongation reachs to 397Mpa and 3.4%.