The Preparation Technology And Microstructure Performance Research On Super-high Strength Al Alloys By Spray Forming

There is a great attention since the spray forming technology appearance,which belongs to flash set technology,the cooling velocity is 10³¹0⁴ K/s,the technology possesses the features of fine grains,homogeneous microstructure,small oxide degree and so on.So the property of the Al alloys could be increased by a big step,and the tensile strength of the Al alloys can be800MPa.There are of great significance for improving the properties of our national production in military industry,which is also the ultimate aim of this paper.The Al-Zn-Mg-Cu series alloys were manufactured by spray forming which containZr?Mn?Ni and so on.The alloys were studied with X-ray diffraction?XRD?,differential scanning calorimeter?DSC?,optical microscopy?OM?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,and so on.The elements and the Zn/Mg ratio were researched on microstructure and properties of the alloy.The extrusion ratio,heat treatment technology of the alloy were researched on microstructure and properties.The results shows that when the elements of the alloy Zn:12%,Mg:2.5%,Cu:1.1%,Zr:0.3%,Mn:0.3%,Ni:0.05%,Ti,B:0.05%,the alloy have the best mechanical properties.And the extrusion ratio of the alloy were more than 9:1,the properties were steady,and the extrusion ratio less than 9:1,there are microhole in the base of the alloy and the higher of the extrusion ratio the better of the alloy.The best extrusion temperature is between 350?-450?,the alloys could not be extrusion when the temperature low than 350?,while the alloys would crack when the temperature higher than 450?.The billets with size of?300mm*500mm were produced by the numerical simulation results and regulate the automization pressure and scanning frequency,the automization system were improved at the same time.The results shows that the solid solution temperature are 450?1h+480?2h,the tensile strength,yield strength and elongation were 580MPa,495MPa and 10%respectively,and the base of the alloy were not precipitated phases,there are coarse Mg₃₂?Al,Zn?₄₉9 phases and Al₂Cu phases in the Al base.The aging results with different time shows that the maximum tensile strength with the aging time of 24h.The reason for this are precipitated phases?'?MgZn₂?which were coherence with Al base.The tensile strength was fall down when the time more than 24h.The dislocations were slice the precipitated when the Al alloys deformation.The tensile strength and elongation are 810MPa and 8%respectively.As the time increase,the fractograph of the Al alloys are changed from intergranular crack to dimple crack when the aging technology became two-step aging.At the same time,the precipitated free zone?PFZ?were became wide and wide,and the phases along the granular were changed from continuous to discontinuous.The reason is the precipitated phases were changed from?'?MgZn₂?to??MgZn₂?.when the second aging time was 6h,the tensile strength and yield strength are the best.The tensile strength became higher and higher when the natural aging time increased of the Al alloys.The TEM results showed that there are G.P zone appearance when the time increased.The tensile strength and elongation are 823MPa and 13.1%respectively.The properties were better than artificial aging.With the help of numerical simulation and die design,the super-high Al alloys components were produced successfully,the percent of pass of the component are more than 95%.The calculation results shows that when the wall thickness is 3.5mm,hydraulic pressure is 9MPa,the safe coefficient is 4.12,the safe coefficient is 1.86 when the hydraulic pressure is 20MPa,the untimate hydraulic pressure is 36MPa;The safe coefficient are 4.58 and 2.06 when the wall thickness is 4mm and the hydraulic pressure are 9MPa and 20MPa respectively,the ultimate pressure is 38MPa.The high temperature mechanical properties shows that Al₃Zr phases pin effect,there are anchoring of dislocations.The grains size are fine and homogeneous,the dislocations block up together,so more heat activation energy was need to glide the dislocations.At the same time,the Al₃Zr particles were heat steability.So the tensile strength of the Al alloys at 100?and250?was higher relatively.