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采用脉冲激光重熔Zr55Cu30Al10Ni5块体非晶合金,研究了脉冲激光频率对激光重熔块体非晶合金晶化行为的影响。实验结果表明,对于给定的能量密度,在脉冲频率低于一临界值时,脉冲频率对晶化几乎没有影响。反之,晶化程度随脉冲频率的增加迅速增加。采用有限元方法模拟了激光重熔非晶合金的温度场,发现过高的脉冲激光频率会产生热累积效应,进而对激光熔池热影响区的晶化行为产生重要影响。其中,热累积效应的影响分为两种,第一种是由于脉冲激光频率过高时,受合金自身热扩散能力所限,前后两个脉冲激光重熔所引起的熔池局域高温区发生重叠,进而引起熔池局域过热。这种热累积效应只能靠降低频率来避免。第二种是试样周围的散热条件差,在激光加工时使得材料整体升温而降低了冷却速度。这种热累积效应可以靠加强材料周围的散热来抑制。
The influence of pulsed laser frequency on the crystallization behavior of laser remelted bulk amorphous alloy was studied by pulsed laser remelting of Zr55Cu30Al10Ni5 bulk amorphous alloy. Experimental results show that for a given energy density, the pulse frequency has little effect on crystallization at pulse frequencies below a critical value. Conversely, the degree of crystallization rapidly increases with increasing pulse frequency. The temperature field of laser remelted amorphous alloy was simulated by finite element method. It was found that excessive pulsed laser frequency had the effect of heat accumulation, which had an important influence on the crystallization behavior in the heat affected zone. Among them, the impact of heat accumulation effect is divided into two kinds, the first is due to the pulsed laser frequency is too high, limited by the alloy’s own thermal diffusion ability, before and after the two pulse laser remelting caused by molten pool local high temperature zone Overlap, which in turn causes the pool to overheat. This heat accumulation effect can only be avoided by reducing the frequency. The second is the poor cooling conditions around the sample, making the material as a whole when the laser processing temperature and reduce the cooling rate. This heat accumulation effect can be suppressed by strengthening the heat dissipation around the material.