铝合金压铸件尺寸稳定化处理的研究

铝合金压铸件尺寸失稳问题是一个普遍存在的问题,对高精度要求的构件尤其重要。本文主要研究失稳的机理。通过高温时效或分级时效消除压铸激冷中残留的热应力,并使合金中存在的过渡相完全转变成平衡组织状态,从而达到残余应力低、组织稳定及尺寸稳定的目的。通过金相组织的观察、点阵常数千Ⅱ电阻率的测定以及相应组织状态的应力测量结果表明,原时效制度下合金组织未达到平稳状态及应力分布不均匀是造成压铸件尺寸失稳的原因。采用本研究的时效制度能降低应力水平和不均匀分布,并稳定组织,可完全消除尺寸失稳现象。同时本研究的时效制度具有节能省时的实际意义。

STUDY ON SIZE STABILIZATION TREATMENT OF DIE CASTING ELEMENTS OF ALUMINIUM ALLOY

The size unstability of die casting element of aluminium alloy is a common occurrence. It is especially essential for high precise elements. The mechanism of the unstability of die elements of aluminium alloy is studied in this work. By using two-stage or high-temperature ageing, residual stress of die casting element in quick cooling is eliminated, and the metastable phases in the alloy is transformed into equilibrium states. So low residual stress, stable structure and unchanged size are achieved. Through the observation of metalography, the measurement of lattice parameter and the measurement of stress in the corresponding state, it is shown that the metastable structure and inhomogeneous distribution of stress in previous ageing techniques cause the size unstability of die casting elements. The ageing system we used can lower the stress level, decrease the inhomogeneaus distribution, stabilize the structure, and thus completely eliminate the size unstablization. Also, the present ageing system can save time and energy. So it is practically useful.