display current portfolio categories from a specific parent

$term_id = $current_term_id;      
  $args = array(

      'hierarchical' => 1,
      'taxonomy' => 'portfolio_category',
      'hide_empty' => 0,
      'parent' => 6,
    );
    $categories = get_categories($args);

    foreach($categories as $category) {

     if( $term_id != $category->cat_ID){
          continue;
      }



      echo '<a href="' . get_category_link($category->cat_ID) . '" title="' . $category->name . '">' . $category->name . '</a><br>';

      }             

I am assuming that you have current portfolio category in variable $current_term_id. However, if you don’t have current category id then and you are in the archive page then you can get it by using get_queried_object()