Disappear the model casts research of modified of surface of magnesium alloy cast

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Magnesium alloy cast is able to bear or endure corrode sex is poorer, the component below harsh environment is easy happen corrode invalidation, become the crucial factor that restricts its to apply more extensively. At present commonly used anticorrosive measure is put in the limitation of different level, be opposite especially the 11~41 of magnesium alloy cast of complex external form.

Accordingly, anticorrosive technology makes the appearance with new research the main task that enlarges magnesium alloy cast to use range. Use casting to undertake exterior modified to cast, technology does not need special device simply, burning in noting a procedure, finish directly. OlivierBeort 151 use die-casting craft preparation project of strong foundation of grain of SiC of high volume mark: National science foundation (50775085) change aluminium radical composite material, and studied be in prefab an effect that adds Mg to be organized to the interface with fuse-element interface, and add the effect of Cu, Zn to intensity of composite material layer. D.

The Coupard 16 composite material that using alloy of CuSm2 of die-casting craft preparation to be base material, the key studied preparation is prefab piece when the bulk mark of the sort of binder and black lead, aluminium powder, think both has very big effect to quality of casting ooze layer. LMPeng 171 in use force for 0.

The condition of 93MPa issues preparation Si3, - Al radical composite material, combinative interface is highest rupture intensity can be achieved 8.

2MPa studied the interface of the stomatic control below pressure casting ooze and composite material reacts, think to react degree rise and increase of temperature as casting ooze. The article is used disappear model foundry technology, use certain vacuum to spend the dip ooze driving force that will increase melt matrix, fluid is passed in the surface of magnesium alloy - originally to answer instead preparation is compound layer. On the foundation in relevant research 8 change material an ancient type of spoon as alloy with metallic aluminium powder one - second is hit one - of the heart. Frosting of department low temperature turns material for pottery and porcelain, alloy is obtained finally to change in cast surface / pottery and porcelain changes compound layer. 1 experiment 1.

Base material of 1 test data chooses AZ91D magnesium alloy, w of its chemistry composition (% ) magnesian; Choice metal aluminium powder turns material as alloy, aluminium powder particle size is 0.

15mm, choice PbO-ZnO-Na2 fastens microtherm frosting to turn material as pottery and porcelain, make up alloy to change respectively, pottery and porcelain changes coating to undertake compound modified studies face of magnesium alloy cast. 1.

The preparation of compound layer uses 2 faces established bubble preparation about, its dimension is 50mmX70mmX50mm, burn dimension to be stuck for cold glue continuously receive figuration. In bubble about surface even besmear brushs the special type painting with good preparation, brush an alloy that makes up by aluminium powder to change coating in about surface besmear above all, wait after its are dry, coating surface besmear is changed to brush in alloy change coating by the pottery and porcelain of microtherm frosting preparation. The ply of every time coating decides according to requirement and other technology parameter. Final dip besmear disappears modular coating, in drying of 50 ° C, use at pouring experiment. Craft parameter is: Of magnesium alloy pouring 800 vacuum spend temperature one 0.

06MPa is pouring below high temperature, polystyrene about produces bate, the metallic fluid of melt of the solution that crack Ft changes coating to contact with exterior alloy above all, the binder be heated in coating burns, metallic aluminium powder fuses and diffuse to matrix, the magnesium in fused aluminium powder and matrix produces reaction to produce the compound between the metal, form alloy to change a layer. Next outer microtherm frosting is fused below hot action, drop as temperature layer of a pottery and porcelain can be formed in cast surface, and with alloy union is good between the layer. Be like,compound layer forms principle graph and sketch map of organization of final cast appearance. The compound layer of cast surface preparation has observation through sweeping face report lens, layer of analytic surface alloy organizes appearance of form of layer of feature, pottery and porcelain. The line scans and can chart test is used at analysing surface layer to matrix main element distributings circumstance, announce the formation of compound layer process and influencing factor. Microscopical the measurement of hardness is in HV-1000 microscopical undertake on sclerometer. 2 tests result and discuss 2.

Compound layer organizes 1 cast surface condition of different coating ply dismantles the structure pouring gotten cast face is compound a micromechanism. Change two coating with pottery and porcelain through alloy is being brushed to change in the exterior besmear of about, wait for the compound layer that alloy layer and contented enamel coating form respectively in the surface after cast is caky. When coating ply is different, appearance of gotten compound layer form also is distinguished somewhat. A is about surface alloy is changed, pottery and porcelain changes coating ply to be respectively 0.

2, 1.

The compound layer that 5mm gets organizes a structure, get in the surface 200Mm controls the contented enamel coating of ply, alloy is formed to change a layer between layer of pottery and porcelain and matrix. When coating ply produces change, the ply of layer of pottery and porcelain of cast surface and alloy change mark of bulk of the 2nd photograph in the layer to also produce change subsequently, be like B.

Change when alloy when coating is thinner, because fuse-element latent heat can make the metallic aluminium powder in coating fuses adequately, and be below high temperature condition retentive time is longer, because this fused aluminium powder can be in matrix of Sunday run diffuse, and produce reaction with the matrix of melt make the 3rd appearance, below the case with make amount of the 2nd photograph particular, diffuse more sufficient, the 2nd photograph on surface layer matrix distributing more loose. After alloy changes coating to fuse completely, quantity of heat can deliver coating of outer pottery and porcelain, after the frosting of microtherm reachs melting point, fuse, form combinative interface with alloy layer next. Change coating to add when alloy thick when, pouring temperature is constant, alloy changes coating the quantity of heat with completely fused more need, accordingly fused aluminium powder issues retention period to shorten in high temperature, and the quality of metallic aluminium powder increases, generate the 2nd photograph to also increase subsequently, the bulk mark that converts the 2nd photograph in the layer in alloy so rises apparently. Outer finally microtherm frosting is fused below more than hot action, the contented enamel coating of certain ply is formed finally in the surface of cast. Preparation is compound when the layer, according to different craft parameter, should adjust alloy appropriately to change, the ply that pottery and porcelain changes coating, painting is too small, generated compound layer cannot provide protection to matrix, too thick meeting brings about coating fusion inadequate, generated compound layer quality is poorer. 2.

Compound layer composition analyses 2 cast surface to come from layer of exterior pottery and porcelain, alloy layer for research alloy matrix the distributinging change of each element, undertake to compound layer line scanning is analysed, if what show. Composition of layer of pottery and porcelain fastens microtherm frosting to give priority to with PbO-ZnO-Na2O, basically contain element of O, Na, Zn, Pb, in the union of layer of pottery and porcelain and alloy layer the interface is in, oxygen element content rises apparently, because the oxide be mingled with of certain amount is contained in the interface,basically be. From magnesian, aluminous element distributinging curve looks, have around the interface besides aluminous element a few outside diffusing to layer of pottery and porcelain, magnesian element does not have Xiang Tao enamel coating to diffuse almost, composition happening mutation is in in the interface. However, come from layer of pottery and porcelain in the transition process of alloy layer, the part that discovers microtherm frosting did not produce choppy phenomenon, this can distributing from composition of element of Pb, Zn, Na the curve sees, especially the metabolic trend of element of Pb, Zn is a process that reduces gradually. This specification is in the surface is compound in the course that change, the coating of pottery and porcelain outside is in after fusing, diffuse to alloy layer, make the interface realizes metallurgy union, this is helpful for increasing combinative strength of the interface. The compound layer face that I different alloy changes coating ply preparation is compound scanning of layer composition line is compound layer XRD analyses Fig.

Disappear of the model although working procedure is simple,cast but metallic liquid is filled model the process is controlled very hard, especially the surface is compound the influence of a lot of element in changing a course. If technology control is undeserved,can bring a lot of blemish, the place in be like is shown, main reason has two sides: It is to be in on one hand fill model in the process, microtherm frosting is eroded, by be involved in be mingled with is formed in fuse-element, as a result of,be on the other hand pouring temperature is higher, magnesium alloy oxidizes very easily, oxide once be involved in arrives among fuse-element, caky hind become be mingled with. Accordingly, if the compound layer of preparation high quality, craft must be controlled strictly, reduce coating to erode in order to reduce blemish, control fuse-element oxidizes, pouring when complete cuttings pick-up, avoid oxidation be mingled with to be in pouring fuse-element of the be involved in in the process. Anyhow disappears the control of foundry technology must have the model certain technological equipment serves as premise, next parameter of repass control technology will obtain relatively the result of beautiful. It is the XRD of compound layer analyses the surface, matrix of AZ91D magnesium alloy basically has A-Mg and P-vAlnMgn composition, and alloy layer besides original photograph, make appearance of AbMg2, Al, MgZn newly still, because be in the course that alloy changes,this basically is, metallic fluid and alloy change coating to contact and make its fused, aluminous content is in in the interface taller, by Mg-Al n duality phasor is knowable, the product that basically makes is AbMg2, Al, in aluminous content inferior place generates P-AlMg of the compound between the metal, be like A.

B is the XRD diffraction analysis of layer of exterior pottery and porcelain, the frosting that makes clear microtherm as a result produces brilliant to change an appearance after be heated, make a variety of oxide appearances, look from thermodynamic angle, the condition that be not brilliant is in taller freedom can metastable condition, below proper condition, be not the change of balance brilliant voice with brilliant condition or smaller energy to the metastable with inferior energy surely surely. After because prefab layer is in this outer microtherm frosting,be conducted heat by metallic liquid, make systematic energy reduces Xiang Jing condition to transform, the contented enamel coating that comprises by oxide is made in cast surface. 2.

What what analysis of compound layer function shows 3 cast face is different technology those who get surface layer organizes correspondence is microscopical hardness, the surface is onefold alloy layer hardness is compared to the change of matrix from surface layer slow, highest achieve 170HV to control, fall gradually to as same as matrix rigidity, formation alloy layer about 300~500Mm is thick. Because there is apparent interface between onefold contented enamel coating and matrix, hardness change is so apparent, fall to be controlled to the hardness 50HV of matrix from the hardness 500HV of layer of exterior pottery and porcelain directly, highest hardness wants prep above compound layer, this king if as a result of onefold contented enamel coating, pottery and porcelain changes coating fusion sufficient. From inside the graph knowable, the hardness of compound layer has an intermediate zone region among change, fall to be controlled to the 100HV of alloy layer from 460HV, although layer of exterior pottery and porcelain and matrix also form combinative interface, but among alloy layer transfers, prevented the direct union of layer of pottery and porcelain and matrix. It is the alloy layer with onefold surface, compound layer and the electrochemistry that did not handle magnesium alloy corrode behavior. This. Close through undertaking to every curve Tafel drafts, get corrosion potential (E) , corrosion current (1) , polarization impedance (R/ (N.

Cm2) . Parameter sees the watch is shown 1 times. Can see from polarization curve and the result that plan to close to its, compare with AZ91D photograph, disappear in the course the model casts exterior alloy to change, compound after changing, the corrosion potential of sample is apparently elevatory, especially compound change sample, corrosion potential is highest promoted 400mV the left and right sides, corrosion current dropped 3 amounts class, polarization resistance is elevatory 3 amounts class, the sample after because this classics is compound,changing processing is able to bear or endure corrode sex rises significantly. Express what 1 different technology issues sample to eat layer of alloy of sample of parameter of potential polarization curve 3 conclusion use compound layer disappear model foundry technology, turn material as alloy with metallic aluminium powder, pbO-ZnO-Na2O fastens microtherm frosting to turn material for pottery and porcelain, vacuum is spent one 0.

Below condition of 06MPa800 ° C pouring, alloy is obtained to change in cast surface / the compound layer that pottery and porcelain changes, alloy layer basically forms compound of alloy of P-Al12Mg17, Al3Mg2, layer of pottery and porcelain is comprised by a variety of oxide. Compound layer is microscopical hardness falls to be controlled to the 100HV of alloy layer from the 460HV of layer of exterior pottery and porcelain, fall again to matrix hardness, hardness change has alloy layer intermediate zone region. Join by alloy layer layer of pottery and porcelain and matrix can raise interfacial tenacity on certain level. Magnesium alloy course disappears the model casts the surface after compound modified, the corrosion potential of cast promoted 400mV, corrosion current dropped 3 amounts class, raised magnesium alloy greatly be able to bear or endure corrode sex. CNC Milling