混合焓对激光多层沉积Ti-6Al-4V合金凝固组织的影响

分别以预合金粉末和混合元素粉末为原料进行激光多层沉积Ti-6A-4V合金,采用XRD研究了预合金粉末、混合元素粉末和沉积试样的相组成,采用金相显微镜研究了沉积试样的凝固组织.结果表明,预合金法激光多层沉积Ti-6Al-4V合金的凝固组织由外延生长的柱状晶组成,且随激光功率的提高,合金凝固组织倾向于由柱状晶转变为等轴晶;随着激光功率由1600 W增加至2700 W,混合元素法激光多层沉积Ti-6Al-4V合金的凝固组织则由粗大等轴晶逐渐转变为外延生长的柱状晶.扫描速率对合金凝固组织的影响较小.对混合焓对合金凝固组织的影响进行了讨论.

INFLUENCE OF MIXING ENTHALPY ON THE MICROSTRUCTURE OF LASER MULTILAYER DEPOSITED Ti-6A1-4V ALLOY

XRD and OM were used to study the phase constitution and solidified structure of the Ti-6A1-4V alloys prepared by laser multi-layer deposited pre-alloyed powder and blended elemental powder.It was found that the deposited layer obtained by using the pre-alloyed powder consists mainly of the epitaxial columnar grains,and the solidified structures change from the columnar grains to the equiaxed grains with increasing laser power.Meanwhile,the solidified structures of the deposited layer obtained by using the blended elemental powders change from large equiaxed grains to epitaxial columnar grains with increasing laser power from 1600 W to 2700 W.Laser scanning velocity has little effect on the morphology of the prior grains in the deposited layer obtained by using the blended elemental powders.The influence of mixing enthalpy on the structures of Ti-6A1-4V alloy was discussed also.