Mg_(96.17)Zn_(3.15)Y_(0.5)Zr_(0.18)合金高压下固溶处理时效硬化研究

AGE-HARDENING RESPONSE FOR Mg_(96.17)Zn_(3.15)Y_(0.5)Zr_(0.18) SOLID SOLUTION ALLOY UNDER HIGH PRESSURE

在4GPa高压下对Mg96.17Zn3.15Y0.5Zr0.18合金进行600-800℃固溶处理，之后在200℃进行等温时效处理．利用TEM，HRTEM，SEM，XRD等分析方法研究了高压固溶及随后时效处理后合金的显微组织，并测试了4GPa高压下固溶处理后合金的时效硬化曲线．结果表明，在4GPa高压下固溶能大幅提高Zn在Mg基体中的溶解度，Zn的溶解度由常压下400℃固溶后的2．11％（质量分数，下同）提高到4GPa高压下700—800℃固溶后的约6．60％，获得了过饱和α-Mg固溶体．在随后的200℃温时效过程中，高压固溶合金在较短的时间内即可获得较高的近峰值硬度，4GPa下800℃固溶的合金近峰值时效硬度高达105HV比400℃固溶处理合金近峰时效硬度（81HV）提高了约30％．HRTEM观察表明，4GPa高压下固溶合金时效沉淀析出相具有很高的析出密度，且析出相中含有粒状准晶I-Mg3Zn6Y相.

Rare-earth （RE） element addition can remarkably improve the mechanical properties of magnesium alloys through solid solution and age-hardening. Increasing the solubility in the Mg matrix and enhancing the precip- itation density are effective measures to improve ageing strengthening of magnesium alloys. In this work, solid solu- tion treatment at 600-~800 ℃ under 4 GPa, and then isothermal ageing at 200 ℃ for Mg96.17Zn3.15Y0.5Zr0.18 alloy was carried out. The microstructures of the high pressure solution treatment Mg96.17Zn3.15Y0.5Zr0.18 alloy before and after ageing were investigated by TEM, HRTEM, SEM and XRD, and age-hardening curves of Mg96.17Zn3.15Y0.5Zr0.18 alloy after solution treatment under the high pressure of 4 GPa have been tested. The results show that, as the rise of the solution treatment temperature, I-Mg3Zn6Y and W-Mg3Zn3Y2 continually dissolved into the Mg matrix, and the solubility of Zn in the Mg matrix drastically improved after solution treatment under the high pressure of 4 GPa. The solubility of Zn in the Mg matrix reached up to 6.60% （mass fraction） after solution treatment at 700-800 ℃ under the high pressure of 4 GPa than 2.11% after solution treatment at 400 ℃ under the atmosphere, and the su- persaturated solid solution α-Mg has been attained. After ageing treatment at 200 ℃, the peak hardness of Mg96.17Zn3.35Y0.5Zr0.18 alloy after solution treatment under the high pressure of 4 GPa could been reached in short ageing time, the peak hardness of the Mg96.17Zn3.15Y0.5Zr0.18 alloy after solution treatment at 800 ℃ under 4 GPa was105 HV, which was increased by 30% than 81 HV of the alloy after solution treatment at 400 ℃ under the atmo- sphere. HRTEM analysis results indicated that the high precipitation density was found in the Mg96.17Zn3.15Y0.5Zr0.18al- loy after solution treatment under the high pressure of 4 GPa, and some of precipitation were particle quasicrystal I-Mg3Zn6Y phases.