The Study On The Hot Crack Tendency Of Al-Cu Alloy Formed By Indirect Squeeze Casting

With the development of modem industry, the need of structures existed strengthen andtoughening and light-weight together is urgent. So the high strength and toughness aluminumalloys has its development chance. The further application of Al-Cu alloys is largely confinedby the casting defect of hot-crack. In the experiment, via the squeeze casting hot-cracktendency test device which is designed by our selves, the shrinkage stress and strain in theindirect squeeze casting solidification process of Al-Cu alloys is researched, and therelationship between shrinkage stress and strain has been tentatively analyzed. On the basis ofthe comparison of ordinary casting and indirect squeeze casting, the effect of pressure andfeeding on the hot-tearing is studied.The experiments show that the squeeze casting hot-crack tendency test device completethe casting molding all right, and have a sensitive and accurate signal acquisition. Generally,this device qualified the test of squeeze casting hot crack tendency. According to therelationship between shrinkage stress and strain, The solidification process of squeeze castingAl-Cu(5%)alloy can be divided into three steps as follows, viscoplasticity step, viscoelasticitystep and elastic step. Hot crack usually occurs in the second step. During the mold temperatureof 100℃to 200℃, the shrinkage stress-strain equation of alloy in the solidification process istentatively obtained.In squeeze casting, hot crack occurs earlier and shrinkage stress is comparatively smallerwhen the mold has a low temperature, contrarily, hot crack occurs later and shrinkage stress iscomparatively bigger. Thus, casts have a big hot crack tendency when mold temperature ishigh, and a small hot crack tendency when mold temperature is low.The hot crack rate of Al-Cu(5%) solidify under pressure of 80MPa is 25% which is ahalf of the rate of the casts solidify with out pressure. Pressure has a significant effect toprevent the hot crack's occurring. This paper studied on the effect of the mold structure on hot-tearing tendency of thedie-casting Al-Cu alloy, discussed mechanics of feeding supplied by slag trap in squeezecasting mold. It is found that the feeding is provided by slag trap at hot spot and the hot cracktendency is decreased, when the solidifying module of slag trap is higher than the solidifyingmodule of adjacent hot spot. The ratio of hot-tearing in this experiment is decreased from27% to 6% because of mold revised.