6082和ZL101铝合金低熔共晶测试与分析

焊缝金属凝固过程中,低熔共晶的熔化温度及其在晶间的分布形态对焊接凝固裂纹敏感性有较大影响。通过采用水淬法得到了6082和ZL101两种铝合金低熔共晶的分布形态;采用差热分析法测试了焊缝金属中低熔共晶的熔化温度和吸热量。结果表明,铝合金材料不同低熔共晶的成分和分布形态有较大不同,6082材料有A l-Mg2S i和A l-Mg2S i-S i+A l-A lFeMnS i两种低熔共晶,其熔化温度分别为555℃和595℃。该材料低熔共晶在晶界以薄膜状分布;ZL101有A l-S i和A l-Mg2S i-FeMgS i6A l8-S i两种低熔共晶,这两种低熔共晶在晶界以连续网状形式分布,熔化温度分别为544℃和577℃。该结果有助于进一步研究焊接凝固裂纹的开裂行为。

激光快速成形Rene88DT高温合金开裂机理研究

采用微观测试分析方法对沉淀增强型镍基高温合金Rene 88DT激光快速成形裂纹产生机理进行了研究。发现裂纹为液化裂纹,具有典型的沿晶开裂特征。激光快速成形过程中,沉积当前层时,已经凝固的前一层沉积层经受再热循环,晶界处的γ/γ′低熔共晶发生液化,在随沉积过程进行而逐渐增大的残余拉伸应力的作用下被拉开,形成液化裂纹。激光成形件组织具有典型的外延柱状生长特点,沉积层底部为近似平行于沉积方向的细长枝晶,其顶部由于热流方向改变枝晶发生转向,在沉积下一层时,道与道之间的搭接区容易存在转向枝晶未熔的区域,因此生长方向偏离沉积方向一定角度的枝晶在搭接区交汇形成晶界,使得该区域成为开裂的敏感区域。柱状枝晶的晶界沿层与层之间具有贯通的渠道,液化裂纹一旦形成就会沿晶界迅速扩展,因此裂纹大体沿道与道之间搭接区域发展。

Inconel718合金电子束焊接头组织与缺陷分析

对Inconel718高温合金电子束焊焊缝及热影响区的气孔、微裂纹行为进行了分析。研究发现,由于焊缝金属中Ti、Al、B元素的偏析,生成γ/γ′以及Ni-B、(Ni、Cr)-Ni3B、Fe-FeB等低熔共晶,在焊接应力的作用下形成结晶裂纹。热影响区出现的液化裂纹起源于晶界处MC的不充分扩散溶解以及块状生成相的局部熔融造成溶质元素的富集。焊件焊面残留的油渍以及匙孔瞬态失衡是焊缝中形成气孔的主要因素。

Cr18Ni12Mo2Ti不锈钢列管冷凝器的焊补工艺

本文通过对一台经过多年使用的Cr18Ni12Mo2Ti不锈钢冷凝器列管密封接头多处发生泄漏的原因调查,针对采用常规焊接工艺越焊越漏的情况,而采了特殊的焊补工艺措施,成功将其修复。

Relationship between amounts of low-melting-point eutectics and hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidification

A systematical study on the relationship between the amounts of different eutectic phases especially the low-melting-point(LMP)eutectics and the hot tearing susceptibility of ternary Al−Cu−Mg alloys during solidification was performed.By controlling the concentrations of major alloying elements(Cu,Mg),the amounts of LMP eutectics at the final stages of solidification were varied and the corresponding hot tearing susceptibility(HTS)was determined.The results showed that the Al−4.6Cu−0.4Mg(wt.%)alloy,which contained the smallest fraction of LMP eutectics among the investigated alloys,was observed to be the most susceptible to hot tearing.With the amount of total residual liquid being approximately the same in the alloys,the hot tearing resistance is considered to be closely related to the amounts of LMP eutectics.Specifically,the higher the amount of LMP eutectics was,the lower the HTS of the alloy was.Further,the potential mechanism of low HTS for alloys with high amounts of LMP eutectics among ternary Al−Cu−Mg alloys was discussed in terms of feeding ability and permeability as well as total viscosity evolution during solidification.

厚板铝合金MIG焊缝裂纹问题探讨

通过对6005A与5083铝合金组合焊接过程中出现的裂纹缺陷进行探讨,确定了焊缝区域所出现的裂纹属于热裂纹,结合实际焊接过程分析了裂纹的形成及扩展机理,并通过试验对焊接参数及工装使用过程进行了优化,最终避免焊缝区域热裂纹的产生。